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STATE UNIVERSITY OF NEW YORK AT BUFFALO
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DEPARTMENT OF COMPUTER SCIENCE
II
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INFERENCE AND CONTROL IN MULTIPROCESSING ENVIRONMENTS
'
Fa
by
~-
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,,",,:~,.:~
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.
Harold
i
II
This work was supported
F~undation,
under Grant
~""",,~i'C1"::o:;:
in part by the National
MCS80-06314.
;
Science
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Ttle
ideas
betlind
infercnce,
as used
Artificial
in
.~.,
(AI)
Intclligence
control
"'-,
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syster:ls,
structures
used
in
are sit1ilar
to those
cther
of
computation.
and
specificallY
are~s
of
certain
,
This
studies
the
paper
discusses
forward,
data
backward
flow
concept,
search.
A model
Consumer
(SPC)
contrasts
those
of
and bi-directional
lazy
is
pOJirs
and
caled
Supplier-Producer-
as a vehicle
inference
and
bi-directional
the
introduced
of
infcrencc;
evaluation
Co!:1putation
/
I-:odel,
between
ideas
for
and control'
moking
strater-ies.
:::
.
Contrasts
.along
.
.
another
dlScusslng
are
static
dlfferentlY
.
and
eager
is
ln
.
disc
made)ln
the
c.
t1ultiprocessing
paper
diMension
'
usses
tt:e
evaluation
an
different
,"
idea
be n e fit
of
5 of
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schemes.':-"~"~:!-!!',ic~~~~"J.,'""",;'
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which
areas
,model
has
science.
r e
and
on
infercnce
uni-~rocessing
"'-,,~,.,'
been'lmPlemented,~;;;~~~~~;":.~.:.;""'c:;i;;
computer
so ftwa
~~;
This.
SiC1Ul a t ions
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'.-~~;:~~~i:()~'t~
of
""c
~ultiproccssing
.:.;;,;~~;~~;'I:;2:;
systems
for
these
control
methods.
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FinallY.
bi-directiotlal
method:.
(computation,
infercnce
~,:\:;":',;;".:,",;;"'"
Dnd
search)
hackwa
ar e
rd
di sc ussed.
coin pu ta t i on
Th e
rJe tllod
s
cot'lb
a U>\IS
i nat
each
ion
of
to
a ssi
for\Jard
st
and
the
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other.
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and
suggests
,
new
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I
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a
pro
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interact
with
a
user.
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IlITRODUCTr(jf~
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control
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the
one
data
stJo\/n
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by
ba sed
on
use
all
input
data.
of
t ions
pr9"ceed
whosc
in
inputs
of
the
Both
technique
the
there
of
the
area
!or\..ar~
these
tile
idca.:'
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is
In
of
u
other
the
Neither'-~ne
present
tr y ac t i on s.
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same
Ci pred eterr.ii
are
,,:ays.
exi~tence
concept.
are
irnmcd i ate
requires
--
or d er
I!Jay
becin.
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da t a-request
~IIJen
la zy eva luat
a request
is.
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ba c kwa rd
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that
a~ y
J\lonc
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Bl-dlrcctlonal
for
and
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cla:;3
:;'.J/cd:
whi CII r e p r c s en t s the
-eaBer
and
J
dimension
stCltic
of
6
tcchniqucs
in
the
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Cll!lOunt
of
in
c
~,,~~
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III oPPoslte
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schclnes,
to
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bc
amount
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parallelism
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TI1cse
specif~cd
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search.
~\roceed
enc t'.
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cor:Jputation
to
evZiluation~
1
val u at ion 3.
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infer
incompletely
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inference
f
a number
:'";~.'~;;"~':if
1.
1
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is
in
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used
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l'lay
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provide
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and
allow.
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Colrlputation,
C:.JPC) 11odcl,
Production
mClkine
of
the
corltrasts
called
is
uf:t\:('en
the
introduccd
the
Supplier-Consumer-
as
inference
a vehiclc
for
and control
mcthod:..
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'--
-
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B
a
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.
.
ti..any of these techniques
;:
9
\/hieh
allows
parallcl..
nlore than
Tile
m
multiprocessing
I
inference
1.1..
Organizat-ion
of
to be executed
in
software-sir:tulalcd
l10W it
improves
metl1odsand
the
operation
especially
of
thc
the
of
the
Paper
,-
I
2 I~ives
11
top i cst
I
multiproce~sin6.
3 explains
techniGues
relRtionship
between
discussion
inforr!\Rtion
in fer en c e.
Der;tons are
and control
the
somc background
0 bed is c u sse d ~
Section
'I
fron MlAltiprocessinG,
computations.
Scction
-I
discussion
and control
-m
-
benefit
one operation
shows
bi-directional
11
Pa be ~
~
the
also
on the
c o'.~t r 0 1,
and
introduced.
S PC rn0 del.
Dre introduced
'
All
of
the
of
production
is
in f c r en c e
s,ho\:n
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(:'-,;i::I.,;
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and acquisition
4 discusses
tIle
result
of combining
forward
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Section
,:,:¥:~~~~'
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methods.
1
c
c;:,;'~::,':';""5~""1~~,i;~,-,
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and contrasted.
the model and computation
of combinations
t """~"'-K;.:'i
and
r:
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.m
back\'/ard
cor:lputation
bi-directional
i
discussed
:1
schemes.
This
combination
col11putation,_inference,
gives
and search,
which
and contrasted.
Section
5 contains
the
summary.
-' c.
1
1.2.
19
licknowlcdgements
I wish
.'Ii
Buidance
11
deal
:1
to thank
and Ddvice
durinE
t'l1C tirne
I
Co!
~y C1dvisor,
in
this
that.
.../ork.
Stu Shapiro,
I have
I have worked
for
learried
witl~
him.
his
c l~rcat
arc
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1:
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this
cleiJl
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the
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Groul.'
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ilnd
f1artins,
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involved
Joao
constructivf:
in
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SUNY
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tile
is
discus.'jions
In.
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wllich.led
to
thesis.
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of
tiri1c
am
very
t~rateful
cditine
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friend.
to
tcxt,
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for
.Duck
being
for
spenuinr;
supportivc,
so
and
for
tnuc!1
bcinr;
I
Last,
J
but
certainly
not
least,
there's
"The
Team.";:,.
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It
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Inference
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Simulating/intelligence
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behavior
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;?2.
Cont.t'ul
Tec)jlliquc:-:
I
I
I
(:ontrcl.
tl;l~
1:lctllOJ
in
c;ilcl
t,1.<.
(xtcnt
,/
:)CI::';...
u:;ed
'..C)
~:::icll
-
in
Ci
t.ili~
I;ror,rar:!
j)c.)Ic::r,
r~l..t(!s
ev..lu~tl::s
t.o
:,;;:!¥;'
:-,.;;,
c"';
,
,
-
.
,
.
'f
IrsFEI:ENCE,
COriTROL AtlV ~jULT1 rHUC£5S1l.G
Pacc
(,
..
I
)
state!:lents.
Ii
evaluatinG
J
required
tecllniqucs
The
all
expressions
do
to
so,
to
purelY
1
difference
between
1
is
1
Der!\ons
range
to cvaluatinc
and from
evaluation
not
studied
using
sequential
what is
froln
inlr:,ediately
nothin~
until
11ir;hly
concurrell,t
methods."
"control"
,'ti-ote
that
and what is
the
"infcrence"
absolut<!.
c'
-;
'"
'.'1.'.;.
J
i
A,rule-based
,
ways.
One charactcrization
flrcd,
1.C.,
..
j
system
i/hether
by
f
the
..n
is
systcm,
until
interpreter
be implemented
.
how the
rules
& nu:nber
are
chccked
a
t y PC
~
~
0
f
base
found
at
with
:'
Thc role
"5].
of
s~'me rDrt.
the
rules
~
intcrpreter
.
DDVis
and King's
whicll
a portion
oS
but
it
DCt i v cpa
cacll
i-lIICn
i p Dn t s .
r tic
to
der:1on has
fire.
a pro'i,r"n
which
is
a y 5 do r rr:;, n t
..1a i tin
G for
A dcl,on
not
invoked
its
II
.
new
pie
activate
ceo
to
t~
tliC
k now 1 e d G e was
and would
kno~;lcdee
rfJ
f
creDtc
uy ~ipplying
oriGinal
add cd,
own
additional
their
pi<..ce.
picces
respective
Tllcsc
new
"
explicitly,
de rI 0 n s
of
t0
"~j:
could
in
turn
[JarBon
kno~lled~c
19].
Dre
consists
:/1
:'-;
rules
J~
Denonz
'c';1
'.
W0 u 1 d
rf1
)
"'-c,,"
'
inference
pieces
:-,:""i_~
;;ocr
(:!',b'
activate
r:lorc der!\orJ~ "IS tile inferer!ces
filtered
down
tllrouch
ch,Jinr. of Jul:,ic.
I:eanwhile
the 1:lain pr°l'.r;IM
could
continue
wit!:
\;Ilatcver
its
prir:lary
task \-1as.
11
.
is
50 me con d i t ion ( s )
va r i 0 u s
"'""1:;
"1~
;",:,~:
,:~'.~~~'
"cc:'~~:
occur...
For exam~'le,
a knowledge
r:1anipulation
procrC1rl
rli~!Jt
implcment
infcrence
rules
as demons.
\,'llencvcr
a
ra
~
:~'~~i~~~}
this
-,
tcrrlinolol~~'
tells
of
whi chI
of
".'
in
-
UsinG
;:;~~~~~I
"""",..,,~
f..
a pas 5 i v eon e .
Hu 1 c 5 r e pre 5 e n t e d u y de m0 n:3 are
'4
,. """,,"",fi~
i."nd' checked'
.
[Davlz
s Y5 tern is
Eind "'i\;.~..:i!t~
:,,' 1
looked
.
data
of
active.,
.or
are
~ !:IC1tch is
in
rules
they are passive
In a Production
!
can
u~;cful
in
.--
bec,.u:3e
kno\-line
-
"a
:111
lot
sorts
of
cor1non
of
tiny
sense
little.
fact.';
r
c~
;j1"":;~;$~t~~:
,
i:
I
~
~
I "FI:: 1\I::r~CE,
AI; to r:UL Tl PReCE:';':; 1 NG
.
..
pop up whcn one
J,
[~;tcels
1
the
19].
is
rnC3in tdsk
if
they
in
thinkinc
about
liroccsses
TliCSC
Charniak,
arc
related
iMpl(;~ented
[Charniak'16b].
states
that
be made as scon as enough information
1
enters
a systeln.
.
]
Toward that
for\~ard."
~£utines.
used
to
ttlan
one
fiis
;
~~~pi~.
activate
demo~'
base
updatcd,
are
~-~ch.
Dll
he int.roduced
demons to
BA5e routines
,
and I:lay be responsil:lc
is
used
for
to
keep
~rc
r~ore
the
d~ta
",~,,~,j;::~,~~'
~~'~~~~~~~
,
when new information
enters
the
system.
.'~1;~~;~~;:;:~~"
,ij~?,~':!
.,. "; "\I!"""-""':!'~"";)~""
..."
Factfinders
.
~
with
fin'dcrs.
f.)oukeeping
inferences
to nake them
implcmented
and £!ct
deMons,
'.
I
demons
end,
intcrruptin{'.
a:. uemons.
should
"look
objt:cts"
c~n work witt:out.
I
1
,$
-
':'
P:ll~C
;;~{,:~f~'~.5;:
that
I
CO:lTI\UL
are
used
to
deal
\~ith
facts
which
are
"'if-¥V'i:\i";:',~!C.,~~~
not
"s",:,::"~j:
1
important
must
1
1
enough
be deCJlt
tCJ be asserted
\lith
in
tile
~
a ~latc~1 on
keep
pro
c c s so r
(r
c"
base,
but
1
whicll:
;'c.~~,,;::~;~.;~~~
;1;Q~~;~I~1,q,t
,,;;".;
::,;$"
;';
.
..~
Some deGree of r:1ultiprocessinB
to
data
the
0r
procecc
sir,,; IJ 1 ate
is
ings.
d.
required
for
Each denon
see
the
':~:,"!f;~
deMons
':;;""',-;1:
:}.';:'-;ic1~
t;;;
may be Bivcn
d i s c us s i 011
'
0 f
,\:cc~..~J.
c
1
]
..
multiprocessing
below)
rnakes
tllUt
thE:
runninc
point
the
prograi:1.
[Charni~k
12].
describes
sitUDtions
\:hen
it
begins
onE rnust
set
and
tlley
Section
that
tile
executinG.
;::;;:...~,;~
'::~'~~
Charniak
are
not
"learned"
LI. on bi-dircctional
'"
.
demons up beforc
:;!
"
col1'JputCit1on.
~
J
!
j
wllere
Der.lons rcpresent
z.:Iy "If
,.
.;:
~
~"
.~
\If:t."
outside.
it
It
is
raininr;
would
ACrCRa
Gcncr..l
and
ill:;tcad
ill
de~on5
JaIl!'.
::;;IY "If
get
wet."
are
rulcs.
is
it
created
A
deMon would
outside.
is
\':hilc
dyn~ll1icallY.
John
will
.~"',
not
'CC;"~
r.E:t
raininr;
and ACTO?;a is
certain
dcwons
rr.ight
'"
~,:
:.
'- ~".~~
.'t;,~
I
c
'..~;C'C""
.c,:,"
"'""""1""'
""c'"
..., .o,.~t
",co
L
r II FEREtl CE .
4
I
I
I
C(,):. T r.0 L i: !; D I! UL TIP ROCES~ I IJG
.
only
I
I
.
rclale
to
ir:~tanceS
tt
of
..
certain
situations.
.t
lo~e
Pa Be'
tilcy
can
bc used
in
C
.:11
.'
uill.lons.
51
!
2.3.
(
Multiprocessing
is
l!ulliprocessinc
u tcchniquc
UScd for
I
cxecution
1
in
a computer
.
system.
speedinG
up
0 - --
~
'root)"
be defincd
gS an integrc:ted
containing
t\o/O or Ir:ore ccntr:Jl
A multiprocessor
I
computer
.
Pl-occssing
I
.
:3ystem
units.
implies
tt.at
pro bra Ins
.
The qualification
the
CPUs cooperate
[ I; aye s 1 C:, p l4l48 ]
By increasinG
on a prograrn',
I
r:lay
the
number of
execution
the
'intcgratoed'
in
the
execution
processes
should
rcquire
of
availablc
to work
less
tirlc
real
to
"
~~"~,~t""
"..;..;;'C ~;;
,.' c-~~iJi~~
,
cumplcte.
There
\Iill
perforril..ncc
wil!i
t
proccssors,
ho\o/cvcr,
rc~ources
in the
Somt: further
I
the
!'.Cirle prOf.rar:l,
I
input/output
of
the
tt:cy
~ystems
tile
nccd
number of
to
!;lcI1tioncc
to (}xecutc
that
in
in
share
'",yo
..,
f!lust
an<; lie
by
different
sh.,rc
I:ayes
[Jre
processes
ne~~ory
thnt
of tIle
and
by the .same oj:-eratill(.
controlled
system.
I
!Iayes
"lso
i n cJ i r c c t 1 Y
Thi~
1
,
nClkes
if n d
d i r (; c t 1 y
di:;tinctjor.
bct~Jeen
the
.;;, (.!i~tirlction
co
dCl:cnd::
u p 1 c ct
on
Ci'Us irvolvec~.
tIle
r:ote
between
f.1 U 1 tip
der.r(~e
that
roc
of
in
standalone,
e s 5 i n -1
5 Y s t e 1:15
~
~oftwarc
t
~
.
Ii r e
not
~i!~Jul~tion
of
I"ultiproce~:.ing,
r e 1 e v ~ n t .
f
I
I
~
.
.
I
,/
,,"
and
.
cumr:1uniccltiol1
the
cJisclJssioli
,
these
distinctions
c:;'o~:::;,:~c.~c"c:~'::
:"C;:;:~~~~;1i!'~~
°j:ii~;i;~;;~,f:,~
;":;:':,"!;c7
lirilitcd
"-
:3y zter:l.
restrl'c-lions
or
illcrc~se
increase
l;CC:iu~e
CPUs must bc able
1
be an n-fold
an n-fold
I
J~
not
of
",c:::;;i,...:ji;~
::"c~:i;
'~
Ct\'
'-"
'"
,
]
~
IlifE/\I::HCl-:,
COl;TiiOL
:;ljLt
liULTlrROCE~~I::G
I':i:~(
11
1
J
LC5Sin(!
'[,ncl
~ultiproce~;5in(:.
Corkill
sy::tens:
J
(Col;,plctelY
t.ccurutc.
1
encl-: Ilodc
Ila::. .:.11 of
~
~
i
tllc
~ computc!tion
Accuratc,
Coopcrative)
sh~rinG
of
able
to
I:,erforr.J
lack
of
data
'.
The
Ilc~!rly
cor:plcte
C1] dcscriLc
[L~5sine
first.
inforl:lution
on itfi
inforx.lfition
cor.1j1letc
thot
it
'ill
~;:Iicl:
,necd:',
n[1(: can
(I-.unctionally
on tlle
otllcr
nodcs.
coMputations
incollplctc
Ci./t;;,
syst(~::lS,
own. FhlC
bctween
cal1cJ
i~
AutOl1orlous)
:;ystems,
and/or
type
cf
t...1O tyrC:5
lland
They
flay
due
to
knowledge
~f
necd
riot
be
a
:~...i~~,
:;!~:;;':~;;;";"lt
c;n
l!lcorithrn
"j.i,;;;-~~~;;f~
Cur.
coopt:r.!t.c
,.,
1hc
i
in
fI
the
t\IO
nodc!s
\lays
\lork
\lllicil
1n
fin
[r;,r1ith
(:1]:
involved
tl1e
;i1Ultl(,rOCCS5in~,;
in
experts
5ystCI':l
t.as~-sl:arinc.,
the
in
r,roblcl~;
report
which
tlley
~rl1t
C!rld reslllt-slla~i:1C,
parti..!l
re;3ults
to
~~%~-1~::~;,t:;,:-:';J~f~~+
~'~'H","'"
~
IJ:
ill
c:ich
(,1'.:.licr C1~ ;?;
1:1
tllcy
worl;.
III
the
forll1er
case,
tllc
probl~11)
is
such
tllnt
"'~~"':~£:l~~~j:~}~~
~;!'
~
i t CCln b c d i v ide din
13
~
w
rlorc
experts
\:orl:inl~
C~lS("S where
the
II
'
bt
.
tt.c
corlllJleticn
..
t.l,t-
bf
,-".
l~
r:.
b c: sol v (d
The other
sub-task
~',
cxp(.rt.,
s to
Clre
i1l1d
by
metliotJ
OIIC sub-task
;Inott~cr
..
- t ask
tot:ct.ilcr.
rczults
of
' ...
t,/I.cra
t 0 sub
50
0 II C "r
1~"~""~:
"",..;1;
..~
'...";:-~~~~r:l
:'i,,;~~":'i;"'~""i
is
us(.'\! 111 ~J"~~Y;;J;:f1~:;::!;'
':hT,~:;;~;~~
nec<:5sury
for
.
"'-j~~:S.
i;:';t~i
comr:unic'tltiOli
-,,;;;j,,'c:;~
"
;
c<:.,,~ry.
,:,-:~:,..~"'~~~:Jt
.'.~"'.j~~",
."""'~~~
'tI
In an Clrticlc
riapl,Oiel
12
~
D If:s5
Ilu:;ic
iii
II
suspended
l)rocc~:.;
/lJ
is
in
rroj:r~(!lli\inl'.
stril.:t
co'ntro1
~lvLiilclule
cont.cxt
control
~iI
"
I
Tllc
Civc
on
t!IC
C1 :;tut.~
dcfinition
il1noVation
..Lility
:11
II0dt,;lc~
is
tJc\:,ivc
of
that
to
savc
I;nl>ro\...
is
nO\1 beil1t.
a r"lodule
ill
c...
thin
~r'onc
t}l~
slructurc.
Li Lir~c,
we
.'
o,lld
l,ultirroc'::~:;il;I',:
r~oucl
cDll
0.11) uf
If
it
""'-..c~~'
'f!lto'
.~ trr:(:
tl
('
CJrlly
one
" corout.i:I(.'
of
::;';;]"c:r'~i,-;1
'
:".':~;*4
its
...
is
.~;;;~-:
: ,..
11;.(;C
"nd
c:f ~;u51'cndcC: ~nir:lc;tion.
r,t:U(:tllrc
j rldt;c(~d ~y
\11 th
(~ontr()l
"as51ni~
modul~:;,
lunr,uvGC:s,
,;~
c~:~:
"c ',c7~:
,:c;:~j~~;,
c~,:,;;~,~~."
,
,
I
"C"
II.fli'(;"C~.::C(~-JTI:fJL
:'
[,lit
~'
;:::L.lIl'ROCE:';~II!G
f,tr';C:
'!i)
1;-
",
.
~
'C
rc..ime.
If
proccssir,~
can
be
thought
of
as
r;oin:
r,)n
~;'":-"silnultaneouslY
in sc'!cral
130dules.
we c:lll
it a
;~ !;~;:: muitiproc('ssinc
rc~i:-.e.
:iultiprocessinr.
is usuallj'
" ;::;:-t ~~~~'-bY scl:cdUlinr:.
tl.rouJ!.h til:1e-qu:1ntuIJ
interru~'t~
"t
'the
systcm
lcv~l.
or tine
allocation
in the lanGu..~e
in t e r pre t e r
u cue s f-rea 1 sou sed. s c c bel 0 \J. J. [ bob roW
..
t.I
[r.
74.
p 157].
Dy simulating
,
!
1!lultiprcce:3sine.
one Gets
a rr:ore dynaMic'
flo\1
II
J
as
of
control
the
-
than
ability
to
in
a
(see.M
strictlY
to)
sequen~ial
do
r:lore
than
SyztCM
one
as
thin~
at
well
'.':fj';;7~;~"
,::~ ., ,:
c;)~:
,-,
a
. .-
.
c
1
,
tiJ:le.
The sY:3t~ci
is
oil'
a uni-proccssor.
still
but
ovcr
tir.le
it
.;::'i:
'"
!
...;
.
,:
appear:3 to be doing r:ulti~...ocessins.
us i n & dcmons.
for ~ x 21;1;>1
e. or for
This
in ference
is helpful
in
":~c,_z,ti~.
~~1'::';'~~~~
te chn i que s wilt ch ~.;~~:,,: '.
,
';t;"'f" ;'f;
can
then
run I \Jhile
rlemory
5tructurcs
are
beinB
built
f"or,-
I
-,,':c ~~~~~!"
5 i 1;1
U1 ate d mu 1 tip
r
J\
it
I~ultiproccszing
c
;: ~~~.. ..:<~ii.;:;.~:~,t' t
:.;,
~lhE':ther
system,
:"~~'~'
'!1'~;;';~!i!,*:ti~;l';f,
;:
~r:"""
mean
to
-
power
deDctivated.
opcrc.tinr.
,
taken
be
should
"'
cornputinB
i5
:.-',
.
. -\ ", ,
relinqust".t.;s
wIlen
otlaer\/ise.
.
roc e s sin r.
process
process
]
5j.)ecified
~aper
unless
this
read.
in
being
"J::ultiprocessing"
I
story
or
'y,
to
by
.~-:.'J~i;J,i';~;:.'~:;'
"" !:I~;-,'4!;;iIi!f!+
anotller
'"
,,""_i\f~j~~:.":
the
. ~, ,:-~,;:., ;;,,~
':-j,:;r.1~~~:'"
by itsclf.
F:e~sons
;'
for
:j~i~;?,,:~
1
d(~clctivntion
includc:
succe.-;sfully
corlpletinc
an assicn~ent..:1~~i~i'~';",,~
,!~~i'~~;;;;
no
lancer
bc
in
g
ncedr:d
beccuse
of
the
re~ul
t
s
of
Dnotl-.~r
"'~ft~t-
:,"."
."!~~
.
jj
process(
resourccs
cs).
or a procc~.'".
zuch
as til~e
cr
'.;sing
up its
complement
the nur.1ber of inferences
",c'J
of
7"': I'. ':~~;~i~5.:~1
c..;,,<;~::~~. I!
Made. ,," "C~~.'~~~~'~
]
;:;~:.,."
~..-~~'" t
Thc lattcr
1
rc:ason
The ncxt
i:;
c~llc.:
t(;
procE::jS
resourcc-limitcd
receive
processinG.
control
can
be
cc":~O\1
j:~~i'
current
tIle
;J
..-",)"
pro
c
c
s
S
I
Z
r
are
n
t.
..
P
r
c
(
0:
S
5
i
t
has
c
r
cat
e
d.
or
0
n
Co"
w
1"1
i
c
I.
\l
AS-.
"',
,,;z.
J
,1e (! c t i v .. t c d c CJ
r 1 i l:!"
.
ilnimation.
.;a
Pr
:,
j
~
.. %';
,! i:;
n u \1 i n Os s tat
e 0f
'~ i#
~~
';~;~'::":~~
. ~"
s U 5 P f: n d e cJ
"'"
(; v
'lllcrc
is
i 0 u ~ pro c e s s.
.1
--
:'!o rt:.-:uirernent
.
to
return
control
co~ i r. .: ;:u reI y s e que n t. i a 1 z Ys t e 1'1
c
-
~o
.
i,S
,
--;
-~
tile
c"C,:,~:.c"'
.
.,~~" ::~
10
,\"~
"
;;:"'.#"~
~,¥~~:~:'
"'M
..j"",
~
;~".«~~j'
,
!i;,
-:;
.
1
'
.
IIJFl::f:EI4CE,
CO;!TRLL
;.I:r;
=:lJLrrPROCE~SII!G
Pace
I
. . ..,-
Uohrow
and Rapllael
note,
I
proce:iSCS c:ccording
J
a~ rcquircd
by the
control
to ti,e
I
rnultiprocessinl';
J
0
.
J
f
1 ue u c s
.
i
crcate
I
flow
l.icrarc!IY
for
~iMulating
tt:is
sequential
type
:iystcm
one of Many. dcpendinG
takes
to
processes
rc-activate
and sfhedulc
or r.ot.
.
froM
tiler:!.
on the
the
the
use
the y are
systel'l
put
dcsiGr:).
queue onc after
["rocesses
new processc.s
of
is
Asp roc e s s c s ;1red. e e Med c x e c u ~a b 1 e,
An evaluator
1
~llJong the
pass
trce-strlJctured
on d strictly
on a q-ueue -(or
another
can
exccution.
One itlplclnentation
1
i;.
r1ay be allowed
execute,
as they
to
i:"::'
so the
;~:.':~:ti;!;it:~:,
.,~f."!:~"~,:~
of
control
!:lay be very
Stallman
'J-
que u e s,
and Sussman
e c.c h wit h d iff
EL prObr..n.
1
j
que u e ,"
In
dynalnic.
(Stall
ere n t
!:Ian 77]
p r i 0 r i tie s.
11ULTI (I:ct~ay
wh i c Ii con t Co
ins
;;),::f:~;:::"'~~,~~
80],
there
pro c e s s est
use
D number
of
.
t 0 i 1:1
pie me n t . t I lei- r
is
':1'.j~~z,:~~
;';:J:!;~~~i~:+1"
';(rJ:i':'j~~;;i~1!,~
:~.i~~f~f~
il "process
0 be' e val u ate d,
l''~f1~~~'i"
",..c, ".,
,
a l\ d a rl y 0 f
:f:~.:~~f:;
,;..:~t~
;?'~ ,;,~;~
thcse
I
describes
1
(Stccls
proces~es
i!lay
a sir:til~r
80],
Ilave
its
own
orl.:~l\izC1tion
\-1hcrc experts
for
1
queuc of activities
to pcrform.
,
B1]use
I
~
pC1rsed
1
par s cr.
f~spa
I:.tlCY are
tul{en
I
j
in
their
for
(:valuation
queuc
to
distrit'uted
of
Ili~
(constr~ints)
"top-proccss-qucue"
a f{UtI-IIE
queue
hold
and
Hei~er
tile
list
\.'ord-cxpert
processes.
Constraint
wait
of
tl:c:
w':
:Iac}lirle
"1~;.
':It:
on tile
eac}1 rlay
hClve
its
OW!'!
and Small (neiger
of
words
to
naturnl
r sin G 0 f \; () r Cs i s co ffi\>1 e t c d 0 r
off
Steels
be
lanGuClgc
z u s pen d ed,
c;ueue.
..'
1
c".t,
.
1
.
I
,j
~
..'~g;
:,c,'
,4, '
/
1
1
,,;
ii'"',
..',:?o-;,.'...'::\~f'
I
..'
,
:'
.
--
3
.
THE"
oj
,,~¥'1i;',../~';" "':~c*""ri~#,."..!"~",;,;~,*".~~,,,,,.
Supplier-I)roducer-Consurner
The
an~logy
the
PC "ODELf:
I'.
(5PC)
a 1.ypotheticCil
between
inference
and
control
is
IJodel
nanufacturin£
~tructures
,foc
an
situation
discussed
in
i'nd
this
,~"\;
paper.
. Jh e sy stelll
cons i st s of
thrce
part.s:
a produc er .
c:o~
~
.;
.,
suppliers,
and consumers
as ~lIown
in
Figure
,- ':
i
£r~~ucer
Manufactures
nunber
of
only
supplics.
suppl ier-.
Each
The conSUMers
one
type
supplY
can
of
is
e~ch
3.1.
The
--
product,
produced
:
use'the
a
by one or
:
~')
usinc
-'~"
~orc
~,:;,
",;L
;~;;::i{::;t~I4,,;~;~t
product.,;:
.
sup P1 i e r
I
~
:
1
.
-1 r
con s ulne r
!i~~t";
..,
._'~: pro d u c e r :. ',"
.J
.,'./
L'
suppli~r-rn
!~!jf:>,r'::;r,1';:'!ii;:::."~
.",
0/:;,
:,~J..:"~
~~",,
.
.
.
I
-1
~
;":lM"C"""i~
consulllcr-n
"::~ii.:,;..;:$..
..
.
S PC
F1 I'... U r e 3 1
t
Di
--
(1
B r CIm of
the
'
a n a 1 o.g y
,...
---
!
Each ncmtJer of
t i rne S
-
t}le
r:loctel plays
each role
at different
~
""
c"'!"
'c;"~:",~~
-
;~;,c:,i
",
"'1~
.";"~
.
1nor
d crt
0 suP.; 1 y its
pro d u c e r,
the
sup p li e r r1:u St
!
;;1
C ",,;"*'i,
J
consume
1
supply
j
the
thc:
liroduct
c!nd consul:1ptiorl
production
j
The
control
flo~l
I
schemes
I
of
an
earlier
rrltes
rlay
procJucc:r,
therefore
and
~o
on.
The
be as varicd
;:"",
.~..
as
rate.
SPC syst.~r!
J
J
,"
"
perfOrl1~j
iMl'oscd
tJifferently
on
it.
de{jendin!.;
Data
flo\l
und
on
lCizy
the
"",}
cO'
";,'~,,~,
~
if
THE
PaGe 15
evaluation
wllile
of
can
supplics.
::
also
t
eviJluation
production
methods
model will
I
oS belnc
r:lcans
of
production,
rncthods
arc
of
acquisition
...
of the
inference
at
and static
cager
Each
.
be looked
will
techniques
and its
be described.
be discussed.
Its
correspondin£
effect
on the
The same treatment
SPC
\Iill
he
-
I
I
applied
to the
production
and
production
both
acquisition
techniques,.
acquisition
\-lill
Four
be analyzed,
combinations
of
consid'ering
I
as contro~
and
as inference.
,
.
3.1.
1
,
I
:;;;:i',;,c;*Z:~;~
Production
l'lcthods
This
model
'"~~ti'l
:, "
~:;':
I
includes
two
types
of
production,
.c""";:~":?"-""""""~~
dota-entry
:;.~;t7.:,:~~
1
;~:ti~':';:4.
(forward)
CJnd dCJta-request
1
d i s c us sed
us
1
model;
(backward).
Each
typc
\1111
.:'.,:if:"~;;'~
be_~c
-
.*,1":":.'1i~~1i~
CJ
n in fer e ,nc co:'"
con t r 01
mc tho din
the
SP C
';;:7::"tK4',?~:
C"~i'~.
3.1.1.
Data-entry
Production
~
'c'1:,~
1
C"""'.
c ';.4;[,
';"C
'-.
The two
1
forward
J
~se of
inferencc,
a~l
InformatIon
1
data-entry
input
share
data
enters
can use it
production
t,he idea
should
methods,
that
be made.
suc/J a system,
all
full
data
and
of':',;,'
and irllmediate
;'.s soon
actors
flow
or
.'.
)_:;;~
as new
rules
";".
w11ict.
""
may do so concurrently.
J
1
.
.:'
,
J
~
i
~
Forward
Infcrcnce
\l/Jen new kno\-lledBc
forward
inference,
inference
I
;'
j s added
rules
to
a SYStCl11 capable
may be used to nerive
.
.,;.;'
_c_--
of
ij
,if:
,*"'c'~"'"
~'!:1![
...
.
TlfE
SPC 110DEL
Pa;:e
1f
.
.
roore
information
purpose
of
froc
forward
new information
[Charniak
In
of
the
have
inference
and
order
for
that
is
which
all
in
of
to
to
Charniak,
find
the
connections
already
found,
fire
antecedent
In
in
matched
system.
I:lad e .
can
to
are
the
their
in fc r c--.r.
~ ,'-:; are
processes
a rule
assertions
rul:~s
Match
According
exists
between
in
memory
76bJ.
input
mode,
it.
a forward
against
inference
the
antecedents
As matches
are
found
conditions
satisfied,'
and rules
forward
a mu1 tip r oc e s sin g en vi ronmen t ,
be set
up for
and they
can
inferences
all
corresponding
be active
to
eac:l
simultaneously.
I
In
~
full
forward
also
trigger
will
continue
been
made.
inference,
the
new inferences.
until
In
all
This
of
restricted
the
resultin~
infer-assert-infer
possible
forward
assertions
may
loop
new inferences
inference,
only
lIave
inferencE:s
\
directly
resulting
Charniai,
inference,"
refers
~lilks
lie
is
that
of
input
forward
deals
are
performed.
inference
with
as "read-time
story
A
understandinr,.
"knowledge-acquisition-time
.
mentions
inference
l~ziness
term
the
to
lJecnuse
more ~eneral
inference."
In:;tcad
from
a dispute
sllould
allowinG
Ilypothc5is
over
be made in
full
to
forward
rcztrict
the
amount
a progrDI!1
inference.
tIle
number
of
in
-
forward
[\-~il~~s 76].
11e sug~ests
of
inferences
made.
TlIiz
hypotllcsiz
st;Jtes
I.I.
oj
.'"
tllat
one
should
." -~--
flOt
introduce
a
,-
?"~~#~t
""
,,';:j(.
.:-
'.
TilE"
.r'u f' ~
~..PC }'(;r..
into
a ',no\lle<lGe
base
. ..:
necr::;~C1ry
superficiC11
unles:;
levcl"
prcference
the
equation
part
of
(x
75].
The
Figure
of
or
Dny point
be
this'
the
boolean
asserted
i.i::
point.
C1l&ebraic
operators.
expression
w is
C1t ,.., mort;
describez
illustrates
,
.
tliDII
:;olvc~
SC1I;1epaper
3.2 .shows
antecedent
& y)
ot
CC1nnot
which
1n terms
when the
when either
problcln
system.
expressed
fire:;
inforr:1at10n
[~Jilks
semantics
The first
only
"more
~
...
;
is
The
rule
satisfied,
as
as true.
'0'
In
the
second
part
of
the
figure.
a
sir:lple
rule.
"All
.
students
.
I
story
co.
:':
is
hur:1an.
attend
school",
sllown.
This
We "know"
\-lhich
rulc
that
might
may
be
see~._a"
students
used
for
~1ttle
go to
reading
a
redundant
-
school.:-but
,,'Co~':i
';.'i,~~~~;;~fg;&
a;.:t;~~.'\:~;~'~"'~
" ,-~,.~':;,!
to
a pror.r
,;,;""¥""
,
need s th is
.
assertion
1
c
c.;C,,~~~"
\.,~"
'J-
,.
'~~~':'c;.;,;;
!
I
:.,~
,;;:,:~
d a tab
only
in forma t i on ex pl i c i tl Y st or ed.
or
in
a rule.
Instead
as e \~i t h in for mat ion
those
so idcntified
:J
ass ~ crt ion
~
as Codemon ill
t hcm
tile
wasting
as
space
v e r Y p 0 s :; i b 1 cst
input
'would
'"
~
'!:O;;;
..,.
~:'
.
,::~'~~~i:~::
~:~1i4";':'~
an
in
"'i;~%;..~,~:~
a b 0 ute
in
mad e a b 0 u t
of
ei ther
'.~!'
~
~'~
the
u den t
,'1..:~:~~~~~~i'
:'(;f:~;;~i~:;;:,~~~
.! . "./"""
t
this
have
:;;:ii~,$!
.
s imp 1 e r u 1 e 1 i k e t his
[\
can
act.:; ",,;;.\!:~;j;t}~
-,~!£J~4.'$"~
a multiproccssillg
system
whicll
does
:~r~iJi~~
full
J
-;":~',,;~i~
for\-/ard
irlfercncc
--
it
c~n
sit
ill
waitinl'"
lookinl~
for
,"'r:
":~,
:1'
a
j.
:;
information
it
that
i~nowS about
goes
to
someone
is
students,
a student
such
and
as tl'.e
fact
then
add
whatever
thCJt lie
or
zchool.
she
:,f
..,;:';::!:;;'~
"
"[(4,'
-i;~;;,,~1f!
~t""".,,;c,:d~
'c'~"~'i~
:.~;~\;~.
'c",ift"i:i~~;\,
"
",'
"-..,~,~
'V~",,":>;';
~
.
Tlli s rule
~/oul d. of course.
only
be useful
in
a
;:!'...,,"":f;;
;;~:;~~
situatior.
",/IICrc
bcinG
a ~tudent
arid
attendinr.
sc!lool
wcre
,~"t;;";o;;,:!,
""Co''Co~::~"
Ii
ir:ir,ort~nt.
Irl
otllcr
:;ituutions.
the
inforl,lation
:~]iI
:ibout
"";;<~
1ft
W
S orneo n cis
uc in ('; CJ stud c n t
co ul d be
\-/uuld not
trii~ger
infc:retlcc.
(
~
\i
i
for\Jar,j
au d e d in
A uscr
a l!1an n e r
could
\.:11i ch
thel!
'
..
-,
.
"t;:t!
:,:;,;;..~,~
.i"::;;~'
"'"CC;;'!~
C .,.c,;:,,~,~
"'c","
I'
I
..I
,...',:;:,!*,!if~":
THE :';PC 110
~':'c::'~1';:"
..
Pa (;t;
1.:.
'"'1'
'~..'J:
..
...~:"
;:',
1
query
the
systern
Cit £! later
time
about
a person
~:llether
J
attends
1
school,
discussion
Dnd trieecr
of
bacl:ward
backward
inference,
inference.
in
See the
section
3.1.2..
,
I
j
..
.
]
Rule:
(x
&
y)
Assertion:
Result:
1
j.
t
A ""
o>o>er
x
.
.
10n.
or
w =>
rlothing,
x is not encu~h
ant e c e den t con d i t ion s 0 f
asserted
alone
forward
to
f
.
V
Asse r t ion.
is.cnouB1I.
1nference
.
tr1gcer
this
other
because
were c: full
z
.
could
ex1sting
be
rules.
c
11 001
1
The
S
ru
result:
e'
recorded
c'i~ci~'~"~"(~':~~~~'~~",~,
the
liary
cat
this
attends
a
bas
c
type
:
systcm,
were
so
asser
t tl'.at
w0 u 1 d not
Inference
C;~;,;'C:C
,':
.
f
c ?,i,~;r';;:':,~
,.~c',
,
ed
fie"
;,::;~~;':;g;!{~~~.~
t 1,e
were
."'"
111
"'-.:-.'},
~
c.
t'..:
~'~'Y;;;fi..
"""o"'iN
,";:"'"";,"
~,,:t~~.f;,
c.'
if
r.gain,
1.a vet
",
f?.;~,,~i:;:";';:-';'
'. ,"'~,':;;,";;;~"'"
:""~."cW'.f;"""'l:;".
,J'"!""""C
of
;', ""'CN'C"'"c.-'~'"
:.',f:';:.; "':-"?i'!:..!~i~C"
.,' ,;,~
-.
0 he
"."",~:i~i;bf"::;;,;:;";~
C
~~
;",i"',
';.;!;,J~.",',""'.';E":"":':'§~:
3.2
r~xamples
- .
Y'
C":~fj
-'--
l-low
"..:"."'i;,i;I'
- ,C~~
AdD t a f 1 0
5 Y :. t em i son
I!
c \/ 11i Clies
c t: e ws the
t r a d i t i 0 .n~~
;:;t,t;j
.._c"
4
j
..'
-"~(!'::lc.:",j:~'!i!:';~~;$%~
",?",.'~.,t,
,..5.,~!, .
:
",
. c--
Z ;j rea
11 ass crt e din
The processes
. '-o:hic}:
of the
de d u c t J.
0ns st
Fi&urc
Forward
l>c:it..
used'j:::'I7;cci;"""":7~,,'.';:i'~';i~t
c.c!:;ty,t'Y'~,;~i"~1'!:;~"",w.",":i~.:"
and Attend~c1Iool(li.iry),
Student(iiary),
made.
':.,;
one antecedent'
. that
5i ~
tn
h i f it cant c e of
e
ex
a new de d u c t ion
.0
as its
facti
y) .
n
(ilar
rer:lain
in the
" t U d en t(I '.ary )
.)
I
c.. ;.,-
ij:~';~!:R~"
,
"ee
0>.
x, w, and
data
base.
used
1. naIl
1
'c"c,,'!i
w
,',c,~,c.", ,'.~,~r~',:",C",
fires,
AttendSchool
,
;
If
base,
'c~P"',"co"';!"°J.:"~~1;"c~,~,~
present.
.
For1 tile
J.
';:i
"
=> AttendSc11ool(x»
.
The rulc
J
:
,)l~
";..::;
tile
:.>t u den t ( I: a r Y )
.
S
;
data
system,
any
x (Student(x)
.
L
.I -
Firlal
t1le
..
is
»
in
I
Result:
i
to satisfy'
the r u 1 e .
c;'"
z is
I
Rule..
z
w
Result:
I
!"""
,.':"";i;~;.
"";i~
,.'"'"
",~
,I
---
;~:~";~
c, ;,;~:
"",,::~~r
.
..c
'.~
%:
,
~
. ,.
~"'r
""~
PC
"
,J
D t;..
t: L
ir; "
p~"C t..
.
conce,pt
of
t i::i E:.
in
cocc:.
An
0 n l~'
opcrZ!tions
u r d!! r
,; r e 5 C r i !J c d
un
rcady.
.
ev;:luati~i:.
operation
is
flo~..
system:::
con
t r c 1
s t rat
~ i~ Y
.
1'.5
described
in
(\:enr.
on
thc:
at
t i r:I e
when
use
this
75].
ooservation
instruction~
the
perforr:led
Datn
ba:;~d
or
that
\1 r i tin
data
datA
an
0 r
its
"tile
one
{:
ore
a~
flo~l'
operation
a
t I: t:'
inputs
depelldency
'datCl'
at
their
concept
(or
an
tile
required
is
,:
/
instru~ticn)
zhould
i rl . u top
coran
'.
opcratlons
c s
be
are
S Y.$ten
~;a its
f1 a d c
.
ZupplYlnB
cxccuted
CJv ail
for
zoon
ab 1c
by
lnputs."
r cqu
ns
t 11e
corn p 1 e t ion
.
.
the
'on 1 y
as
Uecause
i red-
data
a
inputs
data
and
0 f
flow
does
';~"(!.i:T"¥:~'~'~~
",?~~~j~t~i.~~~,?~
not
"!'~l~:~;;,.'",~~~r~;~
process
instructions
tOlay be
rcady
a
sequentially,
for
cxecution
number
of
and
simultaneously
opcration~
.
"thus,
c,;f;l,;f;:';",:~'!t
t:1Btlly
<~~'~,~:'":}'-
,
concurrent
cor,lpu
t;.
t i on
i ~
~
natural
cons
l!qucncc
of
:;:;,':;:;,;,';;
thc
data
-f10\.j
conccpt"
(u~nnis
60J.
'
;';}..~:;
,';:":..
~'c;,",c:;);'
c:J~;
~
D.lta
f10\1
pro(rarns
;,re
cenernl1y
reprc.sentcc
as
procrnl:!
";(
"
f 1
;: r C) phs
0;1
tIle
by
truph
~I i t 11
for
0 r 5.
-
ttie
function
,~
act
arc
~
-
expression
nu~e
an c
l 0 ken
---
"6=3*2."
circle
a
inside
.
Fir;
An-
actor
is
"*",
It>",
s
(e.n.,
3. 3
11r e
s!
lOW
j
,;
c,t
S
,",c
,o!!',-
specified
,
:,"'1t
"r:lcrge")
,
Va 1 u e
~nd
u Sf. J
is
in
Ct
to
used
c 9 :'J S tan
specify
t
an
operation
expression.
/111
or
CIc tor
an
S
C)ctual
:;:::-"1:
" Ge n c r ~ t c
";:;?'~',;f,,:
';'"f!';';'!~~
;~;
SO::1C
value
.:::s
tl!eir
result"
[llcGraw
79].
To':ens
represent
,,;,~
tl:<:
v;'llu~s
cdrriec
in
ar:l!
out
of
tile
actors
011
input
and
..ctor
is
'.~f'
"f;;
outj.Jut
c..rc~,
rcspec~i\'clY.
In
Fir,ure
3.::;,
tile
"I"
"}:,,'~'
'... :,;,i:~
for
r;;u1tip1il;t,tio:1
0 u t l- u t
cnc
v ~ 1 u l: 5
~ r c
t.1le
"1 r i t t c fl
t;:)kens
0 nth
rcprcscntinl';
e
ti r C 5
tl.c
input
"lid
"~~:,
".~
.
(~~
c..c
...,'h
~
";'~
[.
dr.ti1
flow
I
!
~:,'stel~
is
data-driven,
and
COr:lt)ut~tiorl~
grc
"'of;
"
.
.".,,~~(~,..t~,
.
"
TilE
~
...PC
II
.
r..i.'.C
~
..!.
::~'~:;:~"\;',;
by the input
triscercd
d;It...
rlu~1;;J~1t~U<'I~c:-
because
of
thri
ClIJplicativc
76,
79b)
lClnBua~es).
arcs
its
:10 n(!t
of
for
the
output
arcs
Firinc
An exar:lple
of
Exi&tinl~
input/()ut.~)ut
flow
thcnl
two
as soon
however
1,rucc:Jurc:i,
concept.
-. of
fire
each,
are
rules
data
can
Ie systcm.
incorllorat1118
ciescrirtlons-
one tok;en
0
:ip~ciry
of
An Clctor
hav~
a a ln
difficulty
rlCJturc
Dennis
of
they
into
(Sec
datil
f10\-I
as all
of
ent~r
tl;c
[t\rvind
':
its
tile
input
Systen,
and
clear.
show :..ow an actor
a rule
for
tile
proccs~es
Multiplication
its
c-:,
input~.
operator
:";i;\~';IJ,
:' ,",
(".")
",':~c
,,;
.'~Z,i.f;,,;,..c.';~~
is
shown
""
lnput
in
arc~
3.4.
~il:ure
The "before"
have tokens.
but
the
patt'crn
shows
arcs
.:\rc clcar..'
output
'1:;"-.'
,-
"Dfter"
pattern
.
-..
--
1 n put
the
I'
the
in put
how
Clr c S Clr c c lea r
tile
the
,t:1~;~~~)~
!tIC,. o~r~~.~;,,~~;i
,
~ .
operr,tor
;
proccszes
.
2 n d a to ken
th~
r e ~}r c s e n tin
,!i~"~;-"""~.;"
"c;C~~""'(i';li:;'
~"'~";;:~~c";""'t~~
r; ":'f;*¥:~f~(';;'~~
c
":~'r~i;;~"~:1:1
'.".
re&ult
flo~
demonstrate~
tl;at
is
!?;raphs
on
arc
the
outut
r:odcled
(The
arc.
...fter
fiuurcs
for
.
[Dcnnis
19a.
~~enr;
"
pro~ralrl
15.
Lt.'unr.
:;,!'.;i;
""".
'1it:t
.' ;~"':~
0';::1',\'
,
. '7
'
1 :J] ) .
-
~;.";:!
"'::~'L"f;;
-
;c
~
-*,
~i~~;'
-
,
c'
6
-;.
;,
Exa:nj.;le
,
The
of
Go L,ata
--
r:Jultiplicutioil
arc ~ and one output..
them.
,\ctors
art.'
Fieurc
Flow
;..;ctor
r c.
,I
..
"'---, .c.
i~
.:l\.Jays
even i r tIle..
conneC't.ed
I
I
3.3
:1ultiplication
in
{"ctor
s}lo..;n
\-/it!/
t\..o
input
r C:3 h;, v e no vallI e s on
a networ~.:
to
rcprc:=ent
~
r
~
TIlE
'ZPC
00
procral.1
Pa!;e
as
1n
cxpression
of
not
U3C
fi,~ur(:
Thc
in
c
repr~scnts
tllC
that
instead
values
arc
nlecbr[Jic
data
have
flow
syztcn:.:
"immutnble"
Ileld
on
tJo
values
the
arcs
as
lon(;
as
uze.
.. .:
.
are
w
r:oticc
and
79].
.
2.1.
v[Jrinbles.
[licGraw
tllcy
.
3ur~
;:;
--~.~.'
-
'-..~",""",-.
,
'7
*
..
,
1
cur
.
1
r
e
~.
.
1
n
g
k
u
1
e
';:f'
0'
'c':'
.*"..
.
,
F
.
F
.
v''
4
-
for"
t
u
CO"."
-
;.'~c.;
~
;
.
:
1
t
i
pI
i
cat
i
on
~"":!:i;~
",~:,.',~;,i-:,;t,;~~::
;tc"...';
',,~;
"i:;:';J
~PC
110del
io
the
;:'c.o
on
.
Effcct
;;fi;
,-
c..
.;~~.
producer
in
the
t.liC
data
liict1est
flow
ttlrouGhput
~ode.
rate
\lork
iz
\Jhen
.beeun
on
it
2
-t:;:;~
"C,,".
product
i:\!(~~
operates
tiuS
.'c'..;":~
The
a~
soon
m
i
(',lit
as
be
all
part:;
(see
section
3.21.
tl1e
if
tl!is
\/hole
tliC
r:"y
c3t:h
is
be
built
d
i
available.
3C
ussi
because
\./Ilich
on
producers
uses
will
be
as
input.
built
:Jecol!1liosihle
at
into
\..I:enever
their
if
of
earlier
producer
product
l,rocuct
are
the
or
tl!lich
only
but
parts
orders
products
liorllallY.
necessary
of:
in
completer)
tliOSC
the
becuuse
acquisition
tir'1c,
of
Clny
one
sul"lIJart.s,
input
pDI.t~
;,re
prc:sent.
I
'.':~
I
i
Y
-;-_.~.
i'~~;
,
..::!;,:
..
.
n'
!I .'
J ,to
"Ii (. '.I:"
L
'"'~
r' PC
oJ
I,J"e;"';
'"'
--
--
I::qucltion:
=
z
PrO~ralIJ
flo~/
(X
..
y)
+
\..
;:.raph:
.-.
X
':':\*"
"
'-::
-, -
y
- -.
-
~
,
.,
.; +
Z -
--cc
- -
..
;
i
Input:
x
Result:
no
tot
"~~'_."
...
W
action,
because
x is
r i 3 g era n y act 0 r.
not
.
:
enoui~h
c:,-' ""'(
y
In put:
Res u'l t:
t Ii eMU 1 tip 1 i cat ion
act 0 r f 1 res,
sendinB
the value
(x*y)
to the;
.
suIt:
'.c.j;:..~".":"",~,~..~,:>,,.c
the ciddition
actor
fires,
and
result
is placed
on its
output
for
use by any other:
actor.
Final
result:
tllc
arc
,
thi~
part
of t!le
syste/1
i~ in the
s am e ~ t ute CJ
s be for c t I. e e x a r:IpIe.
AIl
in put arc s c:r c c 1 e a r- an d t h c
C!c tor s c:r e
l' r e par e d to fir c . c,
't:
,
",;.',-
F 1 Gu r c
Flo~/
DDt;l
"',;~~t'::;,';"~."
",.'
,., ,
':~::"'
:
:.
::
3. J
Example
,.;.
'~!:':'f
~
.~
-
."
.,~.
,'"
"~f
\./
lie
I~I
,~
~f,-;:,:,r::.,~;'."
add 1 t 1 0 n actor.
Input:
';,,:~,:
,
,'"
t, s
soon
as
a Ion L1 for
use
tile!:.
ue
\..i 11
was t cd.
the
\/110 1 cpr
by
the
ublc
to
110 0 r d e r ::
co rI z um e r.'1
US('
prodl.ct
not
5tockpiled.
output
.
i sex
the product
but
pre 3 c nt,
par t s are
is
com pIc
It
,I C C e p t e d
i r
Wasted
.
?r e
pro d u C c r ;
is
0 d u c tis
l,o!J'efu1ly
0r
t c,
i...
:) E:n t
p e c t e cJ t h D ton
if
\..a i t e c
not,
for
by
pro d u c t s are
inadc
i t
up
for
it
I
0f
is
the
hui 1t
b~' tllc
e
.
l~ xc (: S 5
"
"
.'~f;:
\;,~~:
i
,1
.
-
: ""
%
P. t," e
1
.
1
,:,~;;.
I
c"
,
IT. i n CJ
t ion 0 f
c(JnsU~Jcrs)
nnd
boo ~~:<e e p t n n
<: 1 i
III
1
t;ddition,
]
~ Lalnnced
]
Contrast
tllat
tIle
(e. n .,
(;fficient
tl.c
,:jp.;
to
r e cor (: in.::
use
~ystem
:Juppliers
manner
i:;
Cind
lJininize
\)f
(Jr d c r :i
til1e
in
or(.anizctl,
con:;UI1I~r5
fro n
production.
will
it
is
llf:
chosell
ill
\lastc.
~
/
Th ere
]
by tl.e
ullen
expectcd
C1
r c so me d iff
ere n c e s bet \1c end
a t a f low
(I n d
c'~
,!
.
1
'-.','
...
~",.c.
forward
inference
prescnted
.,:;
here.'
They
arc
not'
1 ..
..'
nccessCJr1ly
yifferences
1n
technique:.
the
ttlel!lselves,
bl;t
.
!I
.'"
system
.
asserts
conclus1on
1tS
.
!
n c ~I structures
or
by
C1
S :. crt
i n r, c xis tin
per~nne~t
~ z t r uc t u r c s
:,;~:';:::-"'.::~,~
~~~.,,;~~;
atf!~-,,~,~ .. "~~
by building
,
";~'~;;;.~!';~ ~
..;,~;i,,;,~",~
"
,,'!\"'
,.~
.,'~;:W~~1;~i~~
,~.;.c:~
t h C 11:1pie 1:1
en tat ion s .
An infcrence
in
c;;.~~.~
e.
~4..~~t.'II'~~:""'~
~~?l'$"~"-~;;;f'~.,..,~
.
"1n
tI
-
; ",;~~.,;:"1;'~1
;~;;!::~~-'c:~;~
I
!
data
flO~,1 sy:.t~m,
no
lcft
bel11nd.
nssertlon
file
record
of
15 r,lercly
C1 cOAlculntion
a tokcn
on
iz
i;n
~
output
~,~ ~,!
-:;
;,rc.
~
I
of
!
wl)ich
datil
notl;in{~
di:;...ppcars
flow
is
~yster:l-~
cllDneed
if
r.ot
--
tlley
but
ti.t'
uscd.
This
arc
is
value~
which
pazz
~ .~i,":':~i~
-C:l:~
and
alonc;
the
I
,,:,;,
;'.;',;c:~~';,~
a cllnr"cteristic
sidc-cffect-frce
.
-'~c"
nrcs.
-j,,-~"':i~;
".t,C';:
c'c",:.~{i
;"~.~:'
I
3.1.2.
I
Prc:duction
DatLi-rcquest
,;:"'"
!
",,='
'
""",
IJot
doing
i n vol v c (~
i n
~ny
t I; c:
work
<.!Ci ... Q
until
it
- r e (; u cst
is
requested
pro d u c t ion
is
c,'
concept
tilt!
t c:c t n i que s,
cv~lu~tion
(tliG
!JoCt:..;;3rd
infcrencC':.
I:valut,tions
1 tJZ Y
.
and
,":;:
~
inr~'rcncc~
u:;cr
or
.jrc
I.cl,!
.:notller
cff
part
of.
lAr-;til
t!IC
"t
c
~...
~:;:,;:
~
'"
~
;;:;#;
explicitly
rc(;ueztccJ
~yster:;.
Ly
tile
.
;' ::"~~
;r:'~L~
-
',.:.:I.;:;?:'.'
,:;;c;:',*,'~
.
-
I
,i
/
'
-
. .- -.
c
..11-
-
~
-,').r.
":c.,",."':
.",
'"c.,."
"'.
;"c"
:;j.~
~
THE :';PC !~ODI::L
:,'
i~.t(;kw;)ru
~4
In f(~r(:IIC(~
An infercncing
ques~10ns.
of
The
01 computer
provcn.
wcre
UackwO1rd
;J
Questions
may
proBrac.
and
or
be
they
created
in
inference
1 t c r n at i v e to
uses backwarcJ
systcr:l
is
for ~..or din
infercncc
explicit.
may
some
as
be
goal~
other
part
described
in
fer en c c for
to
from
which
of
[~lack
anS~lf.:r
the
user
necd
to
the
3yster;1.
68]
as
be
an
..."",,-
an s~..e r i n l~.
que ~ t ion
""'::'~\'i
;
.
Suhstituting
requirc
for\-Iard
r.lakin{o; all
number
of
..
-
rules.
lnforr101tlon
.
Dac~:ward
for
Doing
.
\-IhlCh
this
ut
slo'-'
.up tl..c
ncvcr
solves
inference
the
us~ng ,s::~~:c,~.!'~""'.
'c'~'#'~.L¥' .'
input.
know1edze
tJart.',,;:~~~.~~t;
::£~~~,$:~:":{~
hase ':-'.~~~~(;'_'j.k".
:c';.'~;:,;,:~f~;";:!i'
used.
l>e
this
\-lould'~ii'4"~~,.i~;'"~*,.~
:"'- ~"'~~~"."(!~;'.,
""-'-'"
read-time.
would
clutter
rnieht
infercnce
backward
inferences
and IlopelcsslY
trcl1lendously
~/lth
possiblc
-
largc
infercnce
c'" ;;;; .'::..;c\'c; ;;t
~!!i\~f,~:~;.~i*~~~;:1
c'::::;'-~~::,';..;
problcr:a
~;itli
back\lCird
'~:J"';f~";J;:f'~~
~'::~;1~~'~~~~
~_!Iainin~.
TIle~.
,1301inst
the
thc
consequents
about.
Tilose
.
for each rule
rul~s
of
are
found.
question
rulcs
u5ed
the
to
systeIl1
beinG
wl,icll
?sked.
the
try
to
can
use
is
r:latcl,ed
"."i:;\~;-";:,,~l
I:no\..s
,,:,{\~"'ij~i
5ystCI:l
derive
the
tile
rule
\. ;,!.'},,;:;.;':~i,
;,,:~~,~lJj;~
';~i~;;;~:1;~,~jI
":':J\!.,~.;':;;.;~~
',~,," i:;
answer.
if
it
can
:rl!,,~c.
"'
5110\1 that
the
cJntecedent
of
the
rule
holds
in
the
current
'ic
";'::~J:i,~~;;;;':~
~
::"';Ci(S~"";.;i#{
.,
environment.
r~
r u 1 c ':;
This
requires
clrl t e c e den tag
a ins t
Matching
the
the
pattern
in
the
aSS e r t e d k now 1 cd g e in
the
.::7'~~;;'~~~{;"~
!'~ci,.ft~t
_;ft:~::.
dat a
,
.
..
.
bO)z~.
itself
If
in
superior
a rule
is
con~equent
rulc
must
found ~/11ich matches
the eoal.
but is
po~ition
of another
rulc.
tllcn
tile
be :;1'0'./11 to
hold
in
tile
~
~
Ex a r:JP 1 c s 0 f
IJ
en c ear
:,;;,,::?~,t~
'
e l';i v en
i n F i Cur e
3. C.
.1:,:;,'.~~";;~!~:
;ti:?~~~
.::'::;~il;:~~
::;:;~;'cS~,~
;:'.~~;,';'i~
;, :;:"'5::8,
using
the
zalTle r\llcs
a;.
~
b a c k \-1a r d i Ii fer
""J
!!,,;,;':::'~;~
game cnvironmc:nt.
!
':'I:)",
,'!f.
th a t
b a c k ~Ia r
r
/
as in
tllC
for\o.'ard
ir.fcrence
ca:;c.
I:ote
",:;(c~ZM;::~,"
\:i;.:[~-
i
rI
f (; r en c e i s t r i r; g ere d b ~t que r i e s (C';Ucst ion :3
-;--
;$/~;~cC'.~
,;;:;~;:~c,;j~
,
-
.
,ii,
TJ!E
;.~rc
auol,;t
i:C~i::L
p.:,~c:
forward
, whill,
cora:;f.:qucr:ts)
,,:>:.crt i 0 rI S 0 f ojfl t e c cd c n t s
infcrer.cc
is trieccr~c
,I,
:'
r'j'
.
--
--
Rule:
(x
t- y)
c.ucry:
x?
Rcsult:
or
w => z
!lothing,
x is
of a rule.
Guery:
z?
Result:
not
in
conscqucnt
position
(,issuI1e t!lr3t w l1as becn a:".sertcd
previously)
The ij'stem
Ilotes
that
tl.is
rulc
has Z i,n t!le
consequent
l)osition,
;Jnd trics
to prove tl:..t
its
o:::Jtecedcnts
Irold.
It finds
the cxisterlct:
of L'I, and c;ln thus conclude
tilat
z? is true.
..~~"-,;c.:,"~'
Jiule"
\/x
(Studcl1t(x)
=>
f,ttendSchool(x»
:,';-:'
;;;
'\)ii:~,:,;~'\:r,'f,:;,~:'5~;:
"
Qu e r Y ". I. t ten d Sc h
. 001 ( J 0 h n )
Rcsult:
(..ssume
that
told
that
founc
0
f
t
i,~,j~,,~:tv~,:?~;,~
"""-"",":
";,~~\:
tllc
between
t-.
e
r
system
John is
u
1
c
the
.
~
t
~IClS alrcady
a student).
query
u
den
t
(
J
0
and
the
h
i
n
bcen
i;J]"M.':;',~;
':~'~:;:;~t,
""';~;"~J!i
!::?Z
"".~, "':",!"
A r:Jatch is
)
s
consequent
f
0
un
d
t
0
'
"':c,~:f,;;::'":!i
"',,"
-
c xis t
thDt
in
tile
John
is
5 Ys t em, a n'd the
indeed
a student.
user
i 5 told
i
,
Fin::!l
result:
\.. and ~;tu!lent(John)
The results
of the
are still
deduction~
kept,
bc
and
llavin~
to
tl1CY
Inay
Inakc tile
used
actual
nsserted.
are also
CigDin
CDckward
tIle
sugC£::3t
:'~:
"::;:J;;:
'..;"
~'c,-.~.'~::~
,
'",(
:.)z,_;:1~~::
wi thout
deductions.
FiG u r c 3. (..
Infercnce
Exar:lplc
~,
;,,~;:;j~;i;,ii~;
;0&,
t--j""",£.:
;,,;t
'..;:l.
"'~\,
~a zy Ev~~!£.!!.
In
[F"ric:c::ic,n
,'(,].
Clutilors
ttlat
ccrtain
functions
""C
,
ir.
(siJc-cffcct.-frec)
upplicciliv(;
ir!tcrprctc:J
arr,ur1entz,
1 ;; t (.'r
t i ri \:
ir;
ii
hut
132.')
il'lsteDd
fci;;:11ioti
5!joul(~
: II
laneu3Gl~!i
and
shaull!
"prol::isc
::.lloull'
not
to
evaluatc
cv.;luc.tc
bc
tl:eir
tht.:r"
;It
;:.
'.
,-*
C
;:
i
I
/'
:~'Z%!:
;:~~
';--"
'!;~';;
-
;
I.
I
,
!
11£
':
c.
.
Sf'C
It
;'..\;'..,:~~~\,~:\~;
',;,c, ~"c."
'";""";:,:;""'.'1:;;
,-",
c':;
,
is our thesis
rccord
.
can
suspf:nded
Cc ,;..
fillet!
evill
in:;te;ld
i
be
uf
fields
tile'
l1ith
ot\"~:newlY'r!ll.oc?tCd'
a structure
r~.l)rescntir.t
uatiolt
of
the
rcsvcctive
value
of
thilt
arculllcnt,
tlltc'
~S
10'; done
suspensions
and to force evaluation
that the valuc
is :;elluincly
critical
i
tIle coniputc::tion
function).
then
strict
!
I
By using
evaluating
scnel,e
a lazy
funct~ons
VII
all
tllcse
the
tinc
to the course
of
to tIle value
of tile Maill
are the same as thosc
of a
(neccssary
tile results
evaluation
0111)' at
If
2(,
tllc
drr;UI1ent,
.
syste/:ls
,1/ith strict
imvle/:lcntation
of. cons.
other
clel1entary
fu:lctions
are ablc
to dctect
I
i
that
?:Jr~e
whenever
both
cvc;luator~.:'one
need
whose
results
complete
converGe.
not
spen.d ti!;j~
are
not
,;;:
neCE~ssary.
.
environments
of
tIle
cvaluations
I
in
I
The
the
C;,
suspension
expected
to
of
the
evaluation,
~'Iake up for
the'
is
b,e
I:ept
.~":"
;:c~:~
"' ,..;~
t'he'..til:ie
.'
cxtr:.:
s
l'~:'.;t:~;5,\~!.'
stor&r.e.l);~;i~"~;~;:";"~;~{;ii;¥'~
':
output-driven
c ,!;;~t~:1';r~'~,";;;:~'1-:~\
conputation,
Ct
"-";';;;""~,",f;-""";'
,;~~;;'cJ~~;,,;j!4!o""
r
"'".;,..ci.w""'.'
evalu;!tion
,'i." ~
but
i
Lazy
(,lust
i
1
CJ
c t u ale
!
fun ct ions.
-1
f
dt]ta-drivt'n).
I
.
i
A-"
!
!I
v CJ
1 u a t ion s are
( Co n t rCi st
If
. th
~..l
tt: i:;
the
~f~;::.$;;.;;::\~:::,:;~,:'~
t rig Cere d bY c a 11 s toP RI r:T
d at;).
arru.,cnts
to
fl ow,
\/11i cn
i s
PRIt:T lire
tile
'$,;,~;" ~~":!;;~",:':;;i;;';?'
'~~;,~"~~;tiii,~~!fT
not
c:ctual
.
v C)I
u e s,
s u c II as con 5 t c;n t:;
or
1 i t c r nl
until
finc!s
involved.
.
ev OJ
1u at 0 r h n s ba c ~:e d up ,I S far
as i t can \1i tho u t r C5 0 1 v i n B
.
all
of
tIle
vuriable
bindings.
In that
tu
,.sk
tl1c
user
furtticr
case,
.
of
until
~ne
the
'""'"
',';:~:~~t,1
;'~.:~7;;;f;
tIle
solution
.c-~¥£t;,:~;,
",.,' ,c',
vnriables
continue
all
'
a
rlay
for
t I. e
back-chains
}>roccss
values
then
evaluator
Thi~
it
va 1 u e s,
':';~.,;'~:;;~i:~~
i~
:;;',;;~4i:,;;;rjf~J
",'1.'i.ii~~",~;,;
;f,~:;~~
;\.;~E:v~t'
;.
for
inforl,lation,
:.ce
section
4.3.
,'if
'.c;li
\Ji tho u t
.
cvaluator
I:liel.t
val u e s n e cd
ca
I
cu
c c!11 s toP
1 t .
u'lons.
to
ignore
F.I r:T fun c t ion S,
..11
b C 0 Ut put,
of
t Ii ere
tIle
calculatiu:1z.
i",", nolI
,,!\C
OJ pur c 1 y 1 a z y
c e cJ top
Sinc(;
!'
c,:,-,,'
c;.:::£
110
e r for 1.1 t I: c
\
"'c
;'".
~
.
'"
TJIr:
~rc
Par;c
'10PE
-
..
(CC);IS
I,
II
:;tandard
\\
II
SIJ~pctldcd
\\
\1
;
{
.
n).
\\
II
Evaluation
(Value
!L)
\\
(Value
.
Evaluation
B»
-'.
{
\\
(Susp
A
\1.,
env)
.
,,;:
Where
a
..
(Susp
,-
(Susp
suspcns.ion
t
un
1
.
Fiaure
standard
The
standard,
arl~uments,
part
vs.
or
and
return5
pointing
to
.
of
r:leans
x
.
, '
tllat
'",
tllc
:",
stored
d
.
;,
.'
.
.
i'f;1~;~,i~
.
COtlS
c
".
function
data
the
.
in
evuluatlon
two-part
value
e)
neeCJe
.
env»
-
e is
t
115
Lisp
a
the
1
D
. .
of
3.1
lazy
strict,
~
x
environmcnt
--
;;"!
t..kes
structure,
witll
respective
"':".1"7:~+:;'::';:':.t
two
eacll
iJrr;Ument.
'\;;:~~~~~:;!~;fc
For
-
example,
Fic;ure
3.1
"'l,,;,;:,"i~,tif
sho\..$
how
a
Lisp
.
CO:IS
would
be
evaluatec:
\lh1Ctl
returns
."~~~\:t~~
.'
\.J1th
thc
:.tandard
""".';::;;:.\,,:"~'{~'?
evaluator,
i1nd
"":;i:i1~.~:c;r{5"f
\-lltll
one
~,:~,j~;,~
"i!:"~§¥i~:
s u ~ pen
5 ion
function
5
ins
tea
d
acccs~es
0 f
the
act
u a 1
val
u e 5
suspension,
i:h
.
it
can
e n
CI
5
t r i c t
coerce
':
"~:
,.;::~
the
.
,:f!->~
,:.;.-~
"valu
a ti
...
otl
.',
.
-'"
Su:.pcnsions
:> t, r
uc
t ur C s
are
\...1. i c 11
workin~
wit!-1
c ~l u e n t i a 11 y
CI c c e sse
useful
r:1U s t
\.Jhen
be",
data
d,
1 i k e
1 i 5 t s
.
in
Lisp.
Tile
0 r
t h car
function.
of
~ti1n(~;!rd
!~ u 1;1C n t
In
the
S
(:;trict)
0 r
sor:le
furl
situc
unnecc~~ary
The
;J
fol1o\~ing
-
c t ion
b c for
e
e val
inn!:.,
this
iD
not
..Ior~~
~!}.icli
will
Lisp
fori:!
5~:0\:S
!
-/,
--
;---c..
evaluator
Lisp
be
ho\.J
done.
IJSinb
evaluate:.
U r1
t,
i nG
dcsirnblc
all
t hc
bccause
"
,
c:
Pal~e 28
THE SPC r:CDEL
.
save5
execution
time:
( r 1\I r~T
(C AD R (C 0 t. :j
(0"')
(COrl~ 'n
,
,
\
-.
TIle CADR function
returns
case the
the
its
atom D;
argument.
the
(C)
5econd
iteM
function
PRIIIT
A and C are
A strict
(COt:$
"
evaluation
the
»
in
prints
unspecified
of
'I»»
a list,
out
in this
the
value
of
functions.
expression
would
c.ausE:.:?!.!.
,
of
these
functions,
A and
C perfor:m
wasted
because
I
tIle
CADrI of
If
their
values
be evaluatcd.
tllen
nluch
necessary
the
f." or.)
were evaluated
suspensions
a list
would
t h a n e val u a tin C a 11 0 f
PRIllTi
.
be
nc
COt'S
"".c;:":",,-,-C""
...',!c:;ii';ii~4;s~?~.,;':'
by Ct lazy
be
C.
f.. and
set.
up
.',;;c~:~~~:ci~r;:r~,~~;~:;;
for
"';"_c'~t~~4£~;~J:
';';i.!11'j;j;t~:~~~
;
Somework has to be done
suspensions,
of tl:c
will
F;'f'"
resultlng
functions
If
time
to
.'
li5t
of
C, to
are not
...
thcn
COtJStruct
A and
cDlculations,
expression
tllis
evaluations
to
cotnplex
the
interpreter,
-..
including
is less
.
:'
.
t II e fun c t ion s
but this
. ':;~.~i~t~
.;:j;!i~,..;
On c e t his
lis
t
0f
be
located,
r(';)~~.,
:;,i
;;!)
..;;t,~~;;i~:-
5usl,ensions
and its
i~
value
crcated.
the
returned,
in
CADR of
tllis
the
case
list
can
just-the
:,;~~;;;~!,~
:!,;
...
atOl11 8.
i",.,~
C'
- ;
Effect
on
the
.
,:
t
.'.:.PC f)odel
'c'*'
;,"\~
flo\1
A lazy
ZPC sY5tem
system.
rlothin~
rcque::.t
out
to
for
tl:c
the
eliMinates
i5 built
product.
supplicrs
until
At that
for
tt.e
waste
tIle
found
a consurler
time,
needed
reque~t5
parts.
in
a data
tnakes a
are
sent
"5 a full
-,
"'
cor:lplcment
,
!
;
:
of supplie~
cor:1es in,
the
product
is
built
and.'
,::
sent
to
the
consum~r
wllo
requested
it.
;:c';~;;)
, '~.
1-;--
-,
f~;!r§
i;;,"c'
i'¥i;f~~j~{
T1:£ ~PC r:ODEL
Lazy produccrs
titl£:
wiselY.
IJlar~:et,
use
this
technique.
of
model
porC!llelism
c""
f.f
allow
be
of
beavcr
dore
SIIO\'/~
tlc1ndle
the
t.hcir
Supplies'
tIle
to
is
sar11Jle
:",
'
differ
one
use
unneccssary
\lork
;"..
"
';;":;""'~"'!~i'
c,
:",;;::.""':~1"c.'.';~,;""
..:~1,
[Uaker
CIS possiblc.
of
called
77]"
'~'::
~~~1c
:i i mu 1 tan eo u sly.
7h i s is
not
lio~/ever,
as
as
".,
l~".
;,
the
Tite
"5ililplc
propositions
bccause
r~t:Jf.linin~
ln
soon
futur(~~
rCJrC'l:1ctcrl(.':3~
cnough
ttle
eaeer
c:n "eOleer
evcry
Dre
to
.
.-~
[ Pr CIt t
-
"
~nd assigned
then
all
ttlf:
to
evaluated
a r a 11 e lop
opcrands
era t ion.
return
conditions),
located
i.LGOL-GO
\:0
'
,~..
.
created
of
f
~valuator
Olr.tecedent
2n~i
~hunl.:s,
[used]
s\lllpror,rains
Ii y n ~:~c"
.
I
~
that
rarDllcl."
s t r i c t 1 yap
cv"luntions
li::cn
\. r LIn :'1!1i ~;s ion
are
\.J1\ich are
(~atisfyin('.
Tr;UE
..utl\or~
of
evaluatinc:
and
tlO~1 ('In
!uture~
eacll
of
r:e
ttlcir
starts
"-.Jhicll
i:'
as acquisition
in
c1nd I:~witt
"':...'
valuc
bc~t
,. ,,', ,- :.::_;( .,
rule.
Processcs
tile
c;
.,i~t,t
,
discussed
ClMount of
l~aker
;"
,
reprcsentation
the
on
quality
,
of
wor~~crs's
r!ono...oly
hiCh
;t1:.;,
~S soon
i1
of
. ::;,;.:::~.,'
.~;:.-;~!t;fF,,;
evaluator"
subcx~lrc:i:;ion
3.U
are
colllput~tion
in
Accordit1£~
u:.inc
tlClS l! tlear
structures
and
to
~
in
'
Acquisition
t1\is
pC!f~ti ; ~
,,:...
The control
in
who
one ~/hose produc'ts
:t "3.,t':
3.2.
]'i' '
interested
producer
/,
or
tirc
,
for
75].
till
terl:1inat~d.
\;}Iicll
;:rc..
5il~,ulatinf-:
~ ~;:
..
~l~;~.
'
r
Prol~rarnminl~
cv",luation.
lunr;uar.('~
In
cor.1pilcd
it J-"ortran
languages).
cvaluated.
fenerally
st~tcmcnt
(or
of
their
use
one
subcxprcssions
!.!.!
reGardless
do not
in
uould
ear;er
most
otht:r
uc
commonly
result~.
1\
Lisp
interpreter
in
strict
left-right
.
order.
of
the
;-,
evaluates
a Uoolean
but
as
stops
d e t e r mi n e d
.
soon
11
expression
as
e i t h~ r
thc
vDlue
Lis p nor
expression
For t ran
can
i n vol v can
c";:~~J,~:~
~.:~~t,,;r£\~~
be
,.
.,~::~;
::.~~
y
..
,,;'f~
:¥!
".'
..
con cur r en c y 0 r
:~~
.,~~}:
:~,j:':7
s a vi n g 0 f
( F u t u rex)
\
\\ \
res u 1 t s
.
-"""
-;~:':~
( F~ t u r e y)
I
( Fu t u r e 11) .
-
"f~"
:
I
II
I
;
OR
:
c"C;..C"."'c..c..,."'~~.-
r:'I~
;
Ar~D
"'~:~'~~~;~~7:,
::',:':'
wa i t
for
one
FI RST
to
finish
:
I
"
~igure
"
I]
Example of
3.l::
Eager
-
Evaluation
;~,:1:~
:c~Cilfii'~
~~
Results
future.
of
so the
cofTIpleted
value
ev..luations
of
that
arc
J;Jarticular
saved
process
uy
the
need
-.;c¥f~'~~:
:'.- ',:,\-;",.:'
not
be
i'~~i~~'.i;'~i.-"
"
'-\;~
rccomputed.
For
pc.rallcls
to
this.
sec
[t1cl~ay
80]
for;
..e
c:'
;it11'
.,
description
of
the
-<!at~-collcctor
proceszes
[ Ka p 1 an 7 3 ].
W11c r e c I: art -5 a r (! us cd to
sub g ram r:1()rev
a 1 u a t ion sin
n a t u r all
in
Savet
r1ULTI.
or'
he r c s u 1t s of
an Gu age r roc e s sin C
.
,:::c~,~c:~:':,,;~~
c':...:.,;::~;~c~
:"~::,,:'
;:~::,,'~;r::,~
7i~;:
Eager
evaluation
I
rc5ults
-.-
in
savinGs
of
execution
time
"i~~'
:.
\!.:¥f;~ij:-~:1!_'
,.,,!;~~I
~
-
,",
TliE
:':Pc
but
it
r.iODEL
~b ~C
,
'. i
.'
.
r:Jay also
Irrc.:lev~nt
Crf:C1te Many irrelevant
processes
par a 11 e 1 Iii tho
others
the r s.
finishes.
savings
in
where
arc
but
In
overall
the
which
exalip1c
in
time
FALSE after
calculations
but
Ilave
beLun
Fiuure
3.f,
the
proce/s ses
a series
w quickly
beG in
but as soon as the future
irrelevant.
Uaker
ir.
of
to
ev a Iua ti ng at
for
w finishes,
and Hewitt
in the
lonG
evaluates
note
c~sc
and
TRUE.
1\11
,
samc t i!:le ,
the
tile
that
tl r c
a larr;e
!:lay be found
- c"
t hr ec of
exE'clItir:r.
b c c ome ex t ran co u s when 0 n e 0 f
execution
x arid y return
corup1cx
ttlose
processes.
others
without
beco~e
;,:."
some nieans
,""
:;
of
::t.
large
':,c.
deterr:1i~lnc
irrelevancy,
amount
these
process1nc.
of
"'processes
-
tit1e.
waste
:,
introduce
!hey
scheme to recycle
Garbage-collection
can
a
irrelev~nt
,.;",;;
c'~
'!if:;'"~"';:.:c.,f~
~":;;",;;;':;'~~:l\~\$'c,r,~
a
.,--""
,
";\r::'!'~",...q;y';;',~:;:
cc~ c:;:~,:!Z;;:}~~
processes.
j,.;\ti:O:;,:;:t";'i'i
-
TllC
are
node:;
eai~er
in
ttie
FA/C
producers
of
system
\.JI.ich
can
[Lessin~
share
81)
(pace. 10)
information
"?;(:-::~::;~,'...:Wi
r?":,&~jt
t'~'-::i,..~i
aMong
t
thenscIves
bases.
to
fill
.
in
Gaps in
their.
respective
v
.
COrl{111
and
state
bc "self-directed",
d i r c c t ion
passin~
ttlat
t h c i r work.
ba5ed
Ef
. f C con.
t
--
of
in
t. h c v' PC
nodcs
they
state
of
in
an
CDn eacli
and the
)
on tile
tllat
ext cnt
the
rest
FI\/C
of
{,::.l!;:;,':.ff'
'.::1- ,;,::iif
~i'y
'"~~~:~
c.'\I'
. ;, ;.'
tile
,!c.
t I: e i r I::e s saG e the
,
network.
pro d u c t ion.
first
,1:;~:;'i
*ic):;;"j
;",c-:
." 00 d C 1
'~'."'."!i.j,~
;;:
~pc.;
procucerz
are
concerned
Ii e que 5 t s a r (: s Co
nt
part.
of
each
~"
-~f';:",':""
";.:~~~;~
,
---
I;:a~~cr
]:;
~,~c
.~'ii;,;;iki
systenl
detcrl:1ine
of
"~,t;~
data
en a b 11 n r; them to compute nor e c 0~ pIc t c results.
Lessing
Tile
the
type
0ut
received
to
\:itll
all
will
spEed
0f
the
11(;' u:.ed
of
sup p] i e r s
bccaust'
".f
'-
":..:;,'.
.
'is?
.
32
Pa[.e
~ettinc
than
the
waitinr;
for
outstanding
Partial
of
product
out
the
par,t
hest
orders
productions
the
work
to
consumer
part.
begun
is
Tllcrc
unless
are
involvcd,
the
50lne of
more irlr-ortant
will
;ilway:;
each
part
by conpleting
and '~/aitinc
for
--,'
b~
prcscnt.
i~
a certain
an actual
~
rlr"lount.
order
ueforc
~~;
its
completion.
:~,
;.of;
The
arc
suppliers
there
which
are
not
Clny prcferences
part.
There
acceptance
of
queried
in
any
as to which
special
supplier
r;lay be a r:1inimuln-quality
parts
supplied,
but
even
order,
provi.des
threshold
in
nor
this
for
case,
all
c",;."\.~Jjc"~~;."'~
replies
f
0
-
h
will
not
be waited
o
for
once
a part
arrives
whicll
°
ll;h
Static
enoucll
Evalu~tion
In
:.
tat.
1 c
prescribed
statements
.,
.'
";". "'~"":~"c;~""""!t;li~iC""7":"I'~"';~'1i?c'"
°
e val
u a t
3.9,
x is
before
w.
Unlike
purcly
static
Static
1 C n,
e v
evaluated
some
of
evaluator
(11
u a t
before
the
will
cvaluation
o.f
processes
is
which
evaluate
all
st~ndard
in
requires
is
tl!ut
it
all.
Its
drawbacl:
i~
tlj~lt
cor:1plex
mir;ht
rc50lvl:
on tile
y,
methods
adv,:ntar.e
.
1 0 n
other
rnain
onc:; which
I
.,
"
,.~:,,~~;~!;~~;r"i;;c"f~
~.':J,J"'"'~1'c'
'j",
.
Its
-Eff<:ct
c.,'
is
in
a
problens
is
sequerltial
.;c"2J$
c::'~
,:'
evaluated
its
;'"
,~~
:",:~;
(I
arfuments.
systeMs.
no parCillcli~m
evaluations
mucll
'-;':;'.;,;:;
in
dcscribcd,
of
c.:1.:;ci;,,;,,':{j;;
"::,~..'~
(static)
order,
usually
the order
in whictl
are ~/ritten
dO\'ln in a progralR.
For example,
FiGure
,
?~"'~~
c~;i;':.,""'i:',;~7:(
-",~,,:I:~~~;v~
,.
qualIty.
;::;~~~~:
I
is
delay
nt
siMpler
fa:;ter.
~PC liodel
I
\i';~':
!,,!!
c'c"
'c
"""'00
.,
c,."
""~"",..;;c,!'~,
CC
c""""f""""'.
;;
r
I
-
,
~
~
"
\
T!IE
~PC
!]GDE
Pc.:;e
33
/
---
;,..,"i;f!\
"';;;f1~,-5PC
:oyster!:.
\Jllicra
ollcratc
if)
a
~t~tic
cv;;.lu~tion
~odc
"'~-~""
are
interested
in
IlrC)(juction.
c
a
c
4i;~:lity
Whcr:
h
sup
p
re::;ults
1
i
e
supp1i
but.
i~
the
worth
ion
r:lay
.,1)11
r;-:tt:cr
ncc(led.
act
Tir:lc
but
!>rod'uct
c,rf.'
no
in.
er.
qu.J1ity
parts
r.
CJ!"C
of
rL'quL'st.:;
i
he
'..i.c~11
s
t
a~:
(;
nun
wnsted
osophy
of
r:lethods
and
~rf.'
t
i
~l.!.
1
wait1l1C
tile
sta
tic
cf
scnt
to
f
0
I'or
rcltco
t
h
the
produc
c
slo\..est
e
r
is
tha
t
waiting
/
3.3.
Combinntions,
.,.
Thc two
.
""
supply
hc t\loproouction
~ethod3;'~;UF~;!'~vi;~;:~;~
I
Ci!.n
be
corn
wll1
cd
to
yield
r.tode 1 rea 1-wor]
,
four
cor:cbinations.
:~Or:lC
d sy ~t.CMS in
conputcr
of
~c 1 CI1CC or
.;';"?~!:f',c:;";;
.
:USinc:ss.
"'
-
S
t
CJ
tic
e
val
u
a
t
ion
0
f
(x
t.
y)'
0
r
\1
>
=
"
"
evaluatc
x
to
TRUE
or
.}.
f:g:,;;;:;,~,~c;::;
.,~",",..:,
z
':
"
-
c'l'~!
""c4[
F/\LSE
i;:~
,:""
~:.:~~,
.
-
evaluate
y to
TRUE ,or
x is
FALSE.
\:
"RUE
FALZE.
cven
if
l-"I\LSE.
even
if
~"i~'~J~
:,;,"'{?"
~cf,:,
-
evaluat<:
to
(x
or
i'r y)
is
.
TRUE.
':,,?",
'?
"'"c(;;:
~::ft
',";'c'
"::.-~,~;:
-
a:.:.ign
L:
its
value
fro!!!
the
(jtove
.';~':
e v ..1 u at 1 0 n s .
l;"iGure 3.<;
Ev..!luiJt.ion
F:xal~l:le
;JtHtic
-
If
a
iind
-
---
n
a
log
0
bacl:\/iJrd
u
tIle
I:ro,:uc:ion
sin
f
c
r
E;
n
C
co
:ll:'..I:ocJs are
t
Y
II
(.'::
(f
infercr:cei'cr
0
];Izy
r
\1
a
r
din
cv;-,luatio:~).
I
I
!
.,
---
looked
fer
t':S
..;t
-
bin
li:!~'~-A;!'~+~"1'::#'
en
c
C
J.-
then
0
tt:e
r
l~
Ci
,Ie
t.
c:
f
~:O1'/e
low
'",,:::
,..
.
TI:E ::;PC i:LDEL
Pa[,c
;1,
--""
to
;ir:;:]()LUt.~
lypc~
of
ilip}Cllcllt;lt.i()ns
cQ/;JbillcJtior::.
LAZY/EAGEJ;:
;)
t,rocceds
as fa:.t
requested
frol:l
tliat
in
come
Daker
is
and
is
ordered,
the
\ihen
for
that
IJc\/itt
j;()t.l.
a con~ur;cr
itel!1
sugGest
p~rts
first
a new
are
parts
pnrt
are
some
ord(:r.';
lirocluctiotl
rJecessary
nnd
used.
:;)':;l\~I::~.
until
done
possible.
suPJ..lier:.,
order:.
jllf('r(:II~'~
di.c;cu:-;scc1.
a product
c.S
are
outstandine
Clrl:
:;otllin;:
i':llen
IJroduct.
for
is
of
eCicl1 tYJJc
delivered,
.1n)"
st.opped.
deeree
of
lazy
evaluntion
~
in
their
:;c!lel:le
evu}Uator
I;cttinc
instnnce,
Col!!j)uting
inteGers).
---
to
This
take
c'c:.re of
a li~t
would
t
problel:t
on an open-cndcd
stuck
S0 r~e ~;p e c i f i c d poi n t
tile
of
be
not
thc
used
an eager
cornJ'lltation
:'iquarcs
to
of
tialt
of
tlll
(for
of
_..,:'.~i~~~':~\{;tfi:
tilC
'1:~'-':'" ';,,:
;,!~;;';~:~
-:ii
nfter
,
() conli'utation
co.'
.
to
be COIl tin u e c! u n t i 1 r e qui r e c1
,
"
~'.c,:",{
"~,,
1"~~";
LAZY/STf..TIC:
a I!:adc-to-order
l:othinG
is
conSUI:1er.
lazy/.c;tatic
I~
r:-lanufacturer
done until
that
time,
and only
the
best
:;upplic~.c;
tt.e
and tile
of
Eotl;
the
:i i mil
art.
0
1:1U 1 tip
roc
<:,iecr
DcCjuisitiorl
process
e s sin
to
t II C! t
r;
products
II
/.!
to
In
are
involvinG
s y 5 t e r:l
per
.1 n din
for
tile
a
the
same time
tilan
and/or(
a
I:lanner,
only
r:~dc.
evaluation
The
fer
.'3 e q u c n t i O;i1
r:lore
as
supplicr:i,
tllis
lazy
M i n Girl
at
custorrlers.
from
lJ.'JcKward inrcrcnce.
b c t \.. C C t~ n
at
received
used.
1~,etIIO(! ;:ll()\-ls
bef.in
deManding
GJrc scnt
arc
coMbinations
m-oY !J~ looked
very
is
orclers
"freshe~tU
uc vic\...ed a~ involving
i ~
for
an order
At
best
:;ystem
c ncc
C 1-: c
one
thc
.
I:jay
difference
i n
'J
a
~ i n (~
"
-'","'"c,
a n
inference
:3ane infcrcncE:
"~,-
.
,
..:;.:;'[~,,~:i:iilir";:",;,
TI!E
~PC MCDEL
r.'~y
be
ruJl
U~i~t.
:0ir:lul
stLitic
and
DATA
over
uti
tan ('ousl
'l
cvDluC'ltion
inference
on
one
by
assertion
LIt
Tllis
the
need
sc t.~
restrict
to
cf
the
.
~ s scr t i Of IS
system
to
one
C:i tirne.
in
becausethe-.dat3
constrained
d i f fer en t
\..\)ulc
FLOW/STATIC:
on
;:-
Pace
not
the
flow
aspect
;/ait
for
nornnl
of
all
dcJta
thc
of
flo~
c;>eration
tile
is
suppliers
of
"i);fC",
any
part.
f
\!hen
;111 of
the
requested
parts
II;JVC arrived,
th"e
"
rr.ust
best.
As
soon
productioJl
pro
d u c t
til:le
as
all
The
1 0 n
~e:cidinr.
of
tl1c
It
!.Jeiiri's.
.
finishcd.
;3pend
chccl~
~/hic!1
have
parts
terMinates
on
tIle
of
been
\lhcn
.
quality
cach
of
type
is
decided
thc
OfIe
tIle
supplies
:i~;*'"~;~",;,:~,,.
. :,~'t;~,.~~"i;;;.;.t1
.' c::;ii-;"~:","l'~'~:?'i!:f:'
on,
vroduct
1:'#
.
tt.c
is
~""rJJ:;~'
holds
c;:5':~t;;:'-;5~~~3~i;
producc:r
ul:
"
~.'
-:
!,,'"
"
"'A,.,~~r~~:;':
;;~i;"'~;~.
c,:
c
";~.:¥;;:,,,~
'.':;;~~:~fii~,;If
-..
Coin
bin
in
c.
d
a
t
tI
f
1
0
\;
GJ n
d
s
tat
ice
va
1
u
at
ion
~
c
c
m
s
t.o
be
f.
;~<:."~}j'~~~"
:~d:"f~;,,:;'~r;.
contradiction
of
~orts.
Thc
data
flo\/
part
tries
to
procuce
;;;;!§~:":'~!i;\*'
..
LIS
und
mucll
~
bruke
of
tile
on
as
fast
the
as
possilJle,
throuGhput
\Ihile
by
requirinr,
thc
static
an
cvaluation
Ilaif
":~1~~,:f~\~,
puts
of
~',!;:;:I{f
:.",'"~;~~,:;~'" .:+~':~~~~;i
cill
;.";~;~ti~t~~
inputs.
The
data
flow
concept
says
that
as
soon
as'
,~,t:
~
.
all
data
are
present
for
~ny
actor,
it
can
firc.
Static
;S~!!,,~.~.
'"i':4~~,:li(t]:
{i';~:"~J
eviJluation,
I~oi/evcr,
requires
tt1at
expressions
be
evaluated
"~ff;:~,"i;:~]:~1
;;:
in
CJ
predeterr:lined
order.
The
resul.t
is
tIle
,.Icquisition
of
.1""
."~i:';~i;';
::c"~,;~;:;';~~c4!1
:;:;i;;i'c"~;i~j
SUI!plies
rI 0 t
in
b c i~u tl
a
ztalic
order
Uti t i 1 ::11). are
(onc
L1t
p r f~~ Cn t
cl
,
tir:iC)
\-Jitll
productiorl
".;;,~
:;
.
. :".,""~
:,'
OJl.T/. I:LQ\:IE;~G~~R:
proccdure.
(~((:
.
'i!.i.'3
.
.
[.:.-:nn1:;
~s
tl:c
7<;b]
for
:;PC
systcn
~tandf)rd
G:
dcscrlptlon
J.:"Ita
.
"
flo\.J
of
tIle
"0,
,
data
,
"
"~::c""f!~;~
,"
'4~'l5:$'
~::';:.'.~1~'~
flo\/
pro
l'ilneuc;ce
cj II C (,
.
VAL).
The
is
always
pr(.'p;tred
to
c;::;c;;:;:;::.-;':~~~~
~';";li:,!~;..t"'~
/~11
tov .1i 1;.!J 1 e t: (I r t ~ tI r c u z c c1 and
"II
-
0 r (I c r s for"':'
.
;.::,"
i
.~~~
1
Pane 36
..
rcplncer:tents
Only
are
tl.e
first
sent
of
CiS soon
each
as
tYIJe of
tile
supply
proc!uct.
is
will
used
t;':ver
up./
be
.ac:ccpted.
There
does
not
may be excess
concern
the'
t>rodlJct
system.
is
\/Ilich
bccnusc
the
never
~oal
used.
il~re
Tllat
is
to
produce.
The distinction-betwcen
forward
to
infErence
toe
distinction
.
b a c h \1 a r d
1 n fer
between
enc e
.
sub
e que n t 1 ale
.'
...,
,
..,
inference
n V 1 r 0 nMen t 5 .
flow
for
the
5 t 1 t ute
/ .
OJ
data
substitutcd
betwcen
forward
.
..
is
the
d
datu
pt.irs
flow
wtlen
is
s'ilTlilar
lazy
evaluation
pairs
In.
It
d iff
1S
in rnultiprocessine
the
with
ere
".
,;,;...'.~:j";':':'"~i;~
n c e c ,;~';;;'\:r';:~:i:;;~t'iit~
."
'r,.,!,~;'-;'-"
and
.'~,;r~~~:
(~.,.
"'\C;~.;:4;~;~~".ii'i;""
:..;;,"
f",.;;;~\f"!~~,~:~"~;';;;~,~)"
~
..,
,." .
.
~it;
;:{i~,
'~""~f~1
~
I~I-r;)Ir::::CTI{jI:f,L
.
COi1PUTI,TIO;1
11. f~I-DIHI::CTI(iijf,L
All
.
of
bee nun i
tllat
the
- d ire
triggered
of
-
or
d i s c us sed.
In
I
the.':
product
tile
- parts
of
llave
1:0
:.1ere
~
and
.fhlS.
cla.:;s
f.
been
(data-driv-en).
,..~
fot~l...ard
bl-dlrectlon..tl.
::..,ve
demand-driven
vrescnce
of
fL:r
PC 1:1
CIcIC'1 t II i s r::c ~ n s
might
(representins
ltiUS
for \1a r d a :"1
d b a c k \1a r d pro d u c t ion
combination
.
di~cu~~C'(!
t ern s 0 f
I :)"..-;~f';/.:':7,~
.
c~lled
scllenes
CI specific
by
Uinn t ion s 0 f
A
.
c t ion a I
by an order
COI!Jputation)
COin
COI:rUTATI(1!:
cor:lvut~tion
production
37
PaGc
bac~:\-lard
schel:les
cun
...
be
.
of
COni)~t&tions
lncludes
~nd
comput...:.tion
r:Jethods.
;~,:,"
;'i;~;;,c.
:L;~;,~~~jc;"
:;::~r~}~..;=.
"c.~,c~::,~~~
conhinations
of
Uencfits
-
0
of
f the
inferencc,
ttlese
cor:lbincltions
~ c tua 1 nur:lbe r of
col:lponent can dlrect
Dyn;!mic
suspend~d
demons
demons
proccsses.
described
searcfl
savinGs
~onpu ta t ions
tIle
of
space
,1nd
:::!\~~~~;,:";~
!::;~I:fr:-_~:
C'Y:'~..,:;;~1:":;;c;"
""#'~"."1"~""",..;"",,;;;;"
""
per forl.j ed becau s e each
i""ii;",t~
~;"r':~~~~r'?;~?}
other.
j;;'fff&'~f~
";
be introduced
will
These
in
include
f:~~~i~2":*i1!
are
[Churniuk
as a description
different
72]
~nd
ttlan
thc
~.. '.cii!,
of
st..tic
abovc.
.
LJ.1.
Ili-directional
ProbleMs
Se;,I'ch
\:tlicl:
tllought
of
F'il~urc
4.1.
stei's,
,-'nd Olle
CJ:)
tot
~;olved
occupyinG"
;1 st;;te
by
increlnentDl
~~,
space of
r(;~.rcsent5
one
st..:te
r::a)' Ilav(:
a nul7ibcr
is
tt.(-! (;ollcction
Thc 5tQtc-SpC:c~
~o 1 uti ~
arc
II cpr
I
i
of
of
steps
Ci:J sllown
tIle
be
ir.
irlcrel:lctltal
of successor
all
nay
of
0 b] e rl i s r'~ p r f: SCn t e <f b yap;)
tllo~c
stL1tcs.
states.
i\
t I: t Ii r 0 u 2.h the
.'
:--
",C"i'
"jii;~:'!';"'~'
..
.,
.
8I-DIRECT!O:SAL
COr1PUT/\Tlf;:~
Pa:.:~ 3f
/
:;p~cc,
conncctinl~
5t~te.
~c.lrch
rJDy belli
any
path
rcquir<;:d
i~
attacking
i~
tIle
:;t.:tcs
tIle
procc:.s
po s s i 1>1 c Z 0 1 uti
to
of
;In
irliti."t1
findinp;
Cnd'd
it.
[rli1~50n
Therc
;;0]
are
is
(081
tl1CJt patt:.
0 :'iS t 0 a pro U 1 c n,
s01vc
searc:1.
bet\/ct'n
but
'ilany
a eood
Thcre
0 n 1 y () n e
ways
sourcc
of
of
sorlc
of
them.
-
-
f
I
i
..
'/St~IISt~
.I
\ c'
.-tl
..,
,>t5 - \ \
'-
.,
..
"ic:'~~::.,'"
- - O)tn-c: - -.-tg
II
St
\ <,
"
\\
I I
.,,:;~:,..
'
\ I
~tn-1.,
:3
\
\
r."
1
I
St6
:~
c';c.co
I
\
\
Fl. r: ure
Thc
~;tate
.
4 1
Space
hcprescntation
scarch
tccl:niqucs
.,
of
a Problem
Two stRndard
search.
irlitial
r 0r
In
forward
.
~tate.
;1 pat h tot
bc~i'l
with
\ihic}1
direction
\!iti'l
for
both
tile
h eGo
C1l Z t c.t c.
St {~
conl
and wor~~ to\/ard
select\~c
the
bcl';ins
Figure
.
j(:pends
trick
fo!:\-}{-Ird
I~rocedurt:
(in
situcltions,
I
tl:e
exa/:Jl-.le 3ti
is
I
seDrc:l,
are
lies
initial
on tile
in
~t
11.1) and
A b ~ c ~:WD r d
tJ!e
and ~kl/~rc
zor,c
se~rcllcs
sea r c i1 '.J0 u 1 d
st:1t~.
CltJpliccltion.
havinr:
an ~lLoritt,I'i
"
c
I
'l)l-!)Ir.f:CTIOl:AL
(or
COilPIJTATIO;i
Ileuristic)
for
::cl(~ctinc:
l:i-dirl'ct1oI1Lil
lI:lcl:\I./rd
seArch
the
ir/itir.l
to
Rc.t}ler
than
advr!ntaccOU3
two
to
hi-directional
the
solutiull.!TI:e
exponentially
few c r s t D t cst
tree
1'or"';lrci
w}lcrl
...: t:or:IJ>lr:tc
i.s
Poh1
~Incl
t}I':
!J..th
fron
say:;,
searches,
t~:o scnrches it
~un
into
bc:~
-- .
sct:rcii
\.;i~h each cohtributinr.
p~rt
l'f
r,:otivCition
is that
~carcll
trees
;.;ro..-;
znd two slicrter
searctl
diDr:1cters
l;(!llcratc
h a n ,i sin G1 e 10 n Gc r' d i a r;'c t e r t r e e .
l Pc h 1
DcChal,lIJe"ux
for
st:-,tc
01'
at.
tcrr.~inrltf"s
5tatc.
indt'I)Cnd~nt t}le
cor:lbine
is
c:1d
the
somcw!-:at
erowinr,
s t ;Jt c.
frol:)
rej<::cts
in
[1'cCh[tI1pe~ux
Ih<:
IJroblem
rJore
co~p1(;:x
in
0f
initial
of
clir('ctions
of
ti.c
(ivc
therc
and
his
next
a scarc}1
from
tile
pro b 1 e r:! e X i :3t
[lJicho1uon
c~lrdin(11ity
ilnproveu
the
is
one
([',liP!,).
an
selectinr~
t!lat
0 n 5 tot
Algorithlll
A1(:,oritllm
77]
of
~tC1te
sol uti
fDvor
Path
Patll
ul!PA.
,Jlternntion
that
J;euristic
iclt
tile
f. n u mb e r
il1cludin&
Sltortest
I
j~i-dircctionul
[,
hcuristic
-.
~o.Jl
a f;i-dirccticnal
Gives
and
\/lli1c
look
-::::
P 128]
Polll
([)~PA)
s(arcl:
indicatinG
th(';
to
:1 r:ur:-iJirlntiun
TI.c
intersect,
state
71,
i:;
te~l~ni(iu,-,:;.
trecs
stute
~ n('xt
:;c:,r.':1
-.-
sc;:rcl.
t~o
p~~~
(;0,,1
,
66].
f'0111
colI'parison
:
r,rinciple
not-yet
[Pol.1
69],
visited
nodes
(:oI1IJoncr,t
and
rro/;.
providing
tile
!.~~
l,rOI:lisill:':;.
l;ncc
~ati~fie:,;
s t' 1 t: C t e ~
\.J}lil~:1 col~pares
tile
re;;cllable
tilC
by
l-~(;k\/ard
~'articul;:r
I.est
one
ccec
cor:IIJur.ent.
c."!n<.!idutl's
tJ (!ir(~(\.iol-i
sizes
tile
is
i5
choscr:
~)electe'!,
b(:inf:
thc
sets
fror:1
the
forward
or
111(' direction
as
tIll!
us~d
of
for
tllc
r;\ost
nodc
\/J~icll
closcriess
i~
.
I.i-dircctionijl
se~rcl:.
p r c,z ("rl t e tJ II Cr e,
bc' n c fit
!
,I
"i!:c
tlie
~, f'r c ~i a r;1U1 tip
other
tcchljiquc~
r u c c s sit:!~
/
-- ~
c n vir
0 tl ~ Cn t .
"-0;'.
'0'
'c
:
:::,'
or
a
EI-DIHECTIOi;AL
CCt:PUTATIO~1
P.ICC
I~~
.
P:lrCJllcl
i'rOcl'~:;c~
sclcct
Cilrl
Bi-directional
combined.
<~tloo~e
~nd back\o/CJrd inference
t1artins
ct
al.
call
in f c r e n c c [t I art i n ~ 8 1 ]
.
either
c()n
direction,
towards
0f
the
one
interests
full
for ,\1a r c1 0 r
neC(;S5ary,
Dacl~ward
Forwar<1
for
is
inference
"focus
the
full
<~irl'ction5
allC
tec,hniques
arc:
to
result
bi-directional
tile
u~cr
fer e n c e to
systelil's
and
can
l' roc e e din
attentioll
cut
down
thc
fan
."
b a c !-:". a r d c h a i n i n g
r 0 r \01
a r (! 0 r b 3 C~~
W~ r () i n fer c n c C d r c
bCC3use
inference
the
l~Y 2110 win Gin
of
SP e c i f i c I;;0 des
not
to
Inference
\-1hcn forward
0 ut
u~;elj
nodes.
~.2.
--
bc
e~cll
input
initiated
is
used
\lhen
I:lay be initiDted
where
a uscr
whcn
the
it
appll£:s.
asks
a question.
user
:"idds new
,
!
inforrnCition.
TIle
0 lJc r ,I t e ~.:) full
the
bDckward
This
[\lilks
Fo r \1a r din
inference
fits
7~),
"nd
in
the
IIOt
exists,
sinply
need
1y i f
~va1uatiorl.
the y ::.red
This
ssi st
"lazirles5
lclzy
a usC)ble
I-:ay be used.
not
1 y <:n ou g h to.;
\lil~:s'
ide<1 of
becDusc
Qny rule
lJu ton
\litll
fer £:n c e s Inil y be mad eon
a :':nO\ln coal,
cOllIlJoncnt
r 0 r w<1r <1 i 11fer c n c c.
p"rt.
hypothesis"
no goal
for\lard
rule
i r c c t c d ~t
exists.
is
not
the
If
5()~iC
as r cst r i c t e d for war cJ i n f (; r c n c c be C:1us c t tl e s y s t e1'1 i S I~0 t
nccessary
to
triGL';er
prc...ented
a nF:W for\-I:'lrc:
For~::1rd
il,fcrcnccz
fro!::
inferenc~
whicll
c:.lnrlot
!
!I
usinr;
R newly
~sscrted
propo~itioll
infl:rence.
<':<:r:Jon:~.:ay
j;rov(;
-
,j
!)c
crc.:tcd
sufficient
by lJ:lci:~;:lrrl
nll!~bcr
of
~.
~
.
.
LiI-DIHECTIOfSAL
~I}tcccdcnts.
l..s :.oon
c:.sserted,
tile
expected
.
..s the
demons
queric:;
c n t ere d
'c
Paee ~ 1
CO1IPUTf,TIOIJ
In
act.
riis3inc
propositions
Alternat.ively,
30l:!e of
C..11"1
bc M~de beforc
t 11e ~:I e P~ s y s t em,
arc
any
t his
thc
d;Jt:1 h,1S been
i s k no ..111as
,..r"l,rc-conpilinb",
proccsses
saved,
all
at1d is
at
tile
unles~
rulc5
start.
inference.
be used
Another
set
up tl.e
\-1orks because
inference
ti,e
cleared
by the
uscr,
either
for\Jard
or
for
cause
exll~ustinc
to
It
explicitly
can
procedurc
used
of
its
for~'ard
of
and because
bac~ward
demons
allocation
are
proccs:se:.
is
an
inference
resources..
;;~:'".:
Until
~~i~~;~;:i::~i
it
,.."i'C'-'
is
O1:.signcd
t10rc.
and re~ctivated.
the
inference
remains
as
1] den 0 n .
t hi:.
u r e
some
of
_'."iifO:;i~~
'~;~;~~~~;;--:;~
"'Ch",,"'\,-"
'.' ::'~, ..'!7;~
Sorlc
-
,,"
deductions
t h c
U5 e
fllC:Y not
of
r C sou
be
r c e -1
~lJle
i m i t c d
to
cori;11ctc.
pro
c c s sin
Causes
r;,
or
of
t h ~ t
;~_Cc":
. ,':~,";;\;;~~
,t:(:-,:\;(;:~;~
!i:;:,,:,~'
the
required
prcllositions
.
t lie
s c
cas
C s,
t h r C cop
art:
not
available.
In
.
.
t 1 on ~
~iij",
CX1 St :
Quit.
If
-:-
pro CCsse s
an
inference
cannot
'.;'l;,:;r~~
"3'""~';c"';;,,,
..:~#!t'?~¥l~{
--
*
c,"~::"
complete,
tlie
1 n v () 1 v e d (:.] n iJe 10 cat e d .:In d de .c;t r 0 ye d
.
"':i;';'
c,~
cl;;
'"'0
\Jhen
;:,:::;;J~
tlle
nceded
propositions
are
found.
thc
inference
~an
he
c,:k~;
,
S t [j r
t
(~
cI ,I :~[1in,
res
1
t
s
u
n
!1 cI
~
\1i t t. a n c w set
U
S
pen
d
(~ d
pro
c
e
S
of
S
c
s
processes.
are
not
Par t i to1
.c; a
v
f:
d
0
r
~: e
p
,,:,:~!l:;.
,":\-;.~~l'
~',i'.;:,;~!~
.,
c';~)
t
"
'.',~
,;
trO1c~:
of.
rillc
t r i L 11e r f: J a t
Sa I;)e
d c ,~r e c
protJ]
i1 1iJt t' r
11c"n y
* ~uspcnd.
inference
it~clf
c..ln
.,
tile
and
!!.~!:.
<, ~t~tc
:3arlC rule
nicllt
lie
par t i a 11 y e x e c i.Jt e tot
comp1 e tin l'..
11rocess(c5)
be lC'cCited
irl
tllat
tin C,
t j :1 I; s,
Till'
isjltllcn
j
(!r,.. is
involv~d
in
the
Clnd
susp~ndcC.
Tile
of
sus~cn,:Jc(!
t.nination
"
evuluation
.::nd
'";"
'.'1
11(",
I
..
.
bI-ul.,
r n ECTI0
-'--
C' Or" pu ./I~.,. C' ! '
':I.,~'I
J ft l
I"' '~.,
J "C'
.,.I'~
.
lias
becc)l:Ie
I.
s
(j
CJ::I'~c;i,!l
c
s
c
rib
e
type
d
particular
i!1
~:
c
c
t
trieeer
bc
ion
~.
~u:;i'cnsivn
2,
t
p~lttern
prcsent
.in
c:..lleC;;,
II
C
d
(tilt'
thc
data
C:-1
0
n
..1
at
l:Iissinr.
b..se
de:,O:1.
c
he
s
for
its
propositior,s)
and
tllen
rctS.
II"I
t.ili~
~
to
of
casc,
the
demon
opposed
lias
tc;
can
re-do
\o/ork
dynarfJically
cier:on...
cr.eClted,
dizjcussecl
reSUMe
in
w11erc
\lliich
it
::;s
left
[Ctlclrniai~
off
3lrcady
Ci~
72].
without
been
TI;c
11;jvin:~
to
conplctec.
J~
C:~t3
."..;"~
,
dci:lorl
the
bcen
\1
act
0
actors,
r
v
h
i
c
J
lis
"
"
but
wtllcl,
S1 t
u a t 10 n .
\.IJ(; n
I
\,/i 11 fir
i
s
sin
g
SOt
"4-.,
fit
S
,
r
c
q
II
j.3 in
co
r;:1 w5 1 n C 1 n put..
1"..
:'he
0
prcscnt,
'.."
un t i 1 t !: c r. i tis
A.-;I:.
e
11Ci5ot.hers
I,
~.
.
r~
;4r cpr
i
.,"
C;4n nsl{
tI,e
c
d
";c'
uscr
1t
C"~:':i;,;,~;~'~~;;\i',
tat I! .
for
: :'C:'."'!f'{~
the
'c:;,Z~
-
--
needcd
:::
propositions.
lJy
dolnc
so.
the
i'\t:~
,,:"",,"...,:::t:~
a sir...ilar
e~,c nt,
i n a. s u s pen c!cds
rrOl;rcllJ
r
interaction.
C'.s
;';';~~
,~'~;,.
1'.-;:
a:;
t
h
c
co
1:1()
U
t
c:;
t
ion.
be
mi s sin G i t e 1;1
~ nee d not
corn
e
s
b
i
_.<~
i
r
{'
c
t
ion
~].
I,
-~ n s
t~riB 6 e r c x t c n d c d que 5 t ion
'c"~~!
11
',,~~
c
well
..1
~r
7J;~
0
c
1
,
f
:;,,:;~~~
sessions.
Certail".
hiel!cr
priorities
prot:ratl"-;
col:1
rules
can
tllarl
exccutio~
p letc.
be
others
to
P
C\~
and
query
l~lternativcly.
identified
!;e flble
the
uscr
oint-vallJ(!s
!lavinG
to
if
""?;J'
stol~
they
can
"~~*
,
the"
",:~
!---cii~~~
cannot
be
':."f~:$'l~'
t..
a:;si~ncd
';;f};.
'-.:';~;
'-':
cDch
proposition
involved
in
a
dcduction
rule.
.
"':,'
'.'.'.
for
\;I~cn
the
cul:1ulatiVE..
total
spccifi<'d
of
a question
thr~shol{;.
\1!lich
C.:Jr:rlot
itcflJS
can
~ontinue.
pf..SZf:S
a
bc i.!skccl.
but
do
rIot
trirgcr,
,.
'"
Procc~s('.c;
r:Jissing
que
s
t
i
0
II
5
r
e
1:1
(1
i
n
c;
r
LI
~
(I
C
1~1
;-:.
p
e
c
0
n
s
.
C
..¥
\1
hen
the
b
a
c
k
~I
d
tis
s
top
P
c
Co:
d
u
c
toll
CI
v
i
n
r
~
:_"
I
-
.-.
"!:'ii[i'~#'.41
--
':~
'.
~
.
I.;I-lJIRECTIOfJAL
CUr.~FL'TATIO::
Paec 1:3
.
eX;lrIUSt.<.'rl its
ifivolvcu
nore
cor,l;ilcl,1ent
(If
LJre su5penccd
resourccs
co., put a t ion
request
ba c k
nace
ar.iJin
arc
i s
oy
(!cr::ons,
cillocated.
for
the
:.;us~.encled.
~hr1piro'::;
as
rC:iourcL'S,
ready
t h C II S crt
progr.1m.
prO{;rarl,
\'::licll
to
lattcr
c. usc
of
\!herl
hold
us f:: to
involved
the
is
continuc
\1ay
0 ref
Tha
llrocC55t:'S
to
f..nothcr
J;n CXC)111..lc of
COCCI
ttlC
backwr1rd
;Jn 5 \1e r
(;
proccsses
are
sltuation
is
tlis
:i.y~tcm
SUePS
.
Rulcs:
"'"
1. 3tudcnt{a)
2.
(x
t. y)
=> AttendSctlool(~)
or
\.. => Z,
z repre~ents
where
Studcnt(a)
cz':':.
ilre
,',
.
and
"
:;orle
x
\"andw
",
conditions
"';o,c,..",
'.".",,',
~/llic!1
ttlat
~;::
"""".!'
" "".'; :~~t~;':'~;i;k
.
esttlbllstl
~'::;.,.
,,'
.
lS
ona
;~';""
a
.
':;
';c
,
student.
Input:
httendSchool(Joiln)?
'ii.,
:',';
",;,.
[backward
:'
aspect]
.
--
Rcsult:
)(ule
1 is
seen
conscquent
l~..Ja r din
to
tlave
Studcnt(John)
fi1USt be
5YStCI1 tlClS no v;;lues
i fl fer c:n c cis
x
Re~ult:
,";. "c
f?:
/--
eoal
in
,~,
"",:"C,":""
its
position
and is 5clcctecl
for
f c r en c e .
TOll set
his
r u1C,
b CIc
In lJu t :
tile
provcd,
for
x,
but
y or
s us pen d e d a sac:
ttlC
w.
.~;;,
i'
'
TIle
'
e r,10 n .
;
[ for \Jn r d i'!5 P e c t )
If
y can be ~ho\-In to hold,
pc r for 11i n e ,I b a c k \Jr1r din
far
(possibly
c n c to'),
c..n be used to assert
Student(John)
can be used by the suspanded
rule
Attend:>chool(Johrl)
, r,nd the systeln
rcport
this
to thc user.
Thc systcrn
initiates
a r('qucst
for
y.
If non e is r1va i 1 i'jb 1 e, t tl e in fer
s u s pen d e d
.
by
the n r u 1 e 2
;-
, whictl
1 to
can
conclude,
"'
,'~"""'f~
.;~;
a valuE:
for
':
en c e is;.::
..' ,:~
'"
,
Fl '
Bi-dircctionn]
--(1S "If,
eXllert
r. u:;cr
of
or
IJnknown"
in
COCCI
to
.
<!o:n(.iill
tl;j:)
the
ur C
l'
.
..,
. . Co
InfcrL'nce
--
tl:1.:
~,ny r(;qul.':;t
"
oriticn
I",~de
of
by
r~plying
tllc
,
'.;,
"'"
Exanple
of 11icrolJioloBY
[Shapiro
"riot
l,ro,l;raf1.
1ge 1).
';:~i
appli.cable
;\s
~tnted
,
!
';'~~:r
=-
'
I
..
.
:.;!~!)rJ1'r:CTICH/lL
COI1PUT/lTIOII
P:1r;C 41:
.
. .
ijbovc:.
the.-;e
:,;eetion
2.1:
ClcI10ns work
uccau5c
Infcrl,:nce
direction;
rule.-;
and processe.:i
of
c..rl
the
~5SU:1rtions
he uscd
Clnd jlartial
in
r;Cinc in
('itllcr
evCiluDtions
~re.
retained.
A sir,1pl c ex alnpl c of
in
Fi(,ure
Su h s tit
u~cd
4.2.
using
uti 0 n s arc
\..ith
tile
suspended
both
rulc.
shown.
information
to
rules
r; ~d c i n t Ii e fir
second
is
bi -d i r ec t i onCJl in fercnce
the
FiGure
st
r u 1 -: to
A case
and ~ case
ask
fro':;
user
\-I!lcrc
where
for
a 11 o\." . ft
is
to
be
inference
systeM
c. value
shown
2.1.
the
the
is
lIas
nlso
is
enoueh
s}:own.
..
,.
c
~.3.
Bi-dircctional
Cor:1iJutation
Co11bin i n C d a t ~ f low
c1n d 1 CiZY e val u at 1 0 n y i c 1 d s a
hi-directional
computation
sche~e
analogous
hi-directional
il-.ference.
Again,
there
$y.stem
to
at
time.
3ny
prol:lpted
l.ave
nn alGorithm
because
tile
--
/Is described
COli!(Ion e nt,
i sou
P I! I IJT
Tllc
pro.:rat:1
run c t i 0 11S
for\-1arcl
C0 f;1put :1t ion
i:;
used
LI
lazy
evaluation,
1IIIert'
i nit
it
i~
;/
r: i
for
component
depends
or
-d ire
by ttje
no nced
a PRIIIT
the
the
to
use
on wh~t
function.
backward
c t ion a 1 COMput a t ion s
need
to
evaluate
is
data-driven.
arr~ul'1ents
.
cz.;lls
i:3
is
taken
function.
-d r i v en.
to
~Ihich
HEAD
cor:lpon(:rlt.
cont,;in~
decidc
dircction
above,
t put
to
be initiat"d
r1;JY ttlerefore
0f
the
..iction
'
", "-.",: c:i;:t!~~~i~'i
i'.'i",;"" ,
rlatCJ
\.0
i ate G
READ
.
f\
functions.
If
a
for\';<1rd
:3 c. val ue e n t e r s t h c s Ys t erJ, i t
Cippropri;:ltc.
,
flo~J,
-,
;'is
lonr:
..:,;
a
p~rticIJl~r
lJSC
~
"",
.
DI-DIRECTIOi:r,L
i s
COl1PUiATI(It4
<I i r to'c t e <I tow a r (I
no (:xislirll~
tllat
~0&11:o, ltl~n
needs
happens
actor
if
f10\1
opcr"ting
v~llJC
sc t
r 0a1
.
Ir
t I: e r <~ i I r (~
Ci1n bc lJ:;/. I ItY any
in
component?
bi-directiona1
but
one
are
either
a for\Jard
Thcse
questions
prt:sent
or
CiS suspensions
Clc1.or
if
are
for
backward
tilt'
mode?
system
ans..lerec
i
a
input
in
has
::;ection
thrcc
4.2.
,\
choiccs
:
by
process
as to
i
'
11as ~
actions
in bi-directiona1
computation,
t. 0 the options
r r e :0en t e d for
i'nfercn~e
a missinp,
to~:ens
exist
100kinc
~t possiblc
which are similar
finds
lilc
all
\-1IIY do computations
da.ta
c v i 0 ll:O 1 Y
it.
\lhat
given
:~0 1;1cpr
Pa~c ~5
;
',~
.-'
...
1':
\-lhich
ho\i
.
,"
.
~-:'::"":'~
,
c
c,.
"
'
",~.'
to
continue:
.
-
Quit.
The processes
involved
in
an inference
I
,
whic!1 di~
partial
complete
results
aG~in,
the
not
are
arc
saved.
new !Jroccsses
arc
sct
up for
,Ire
dynar:1ic
demons
the
involved
and becomc
:;uspended,
rule
is
the
:1'.
tri(:;gered
inferC'ncc,
but
repeatedly.
The processes
inference
IIone of
\Jhen thc
saine ~~ork may bc done
. Suspe~.
destroyed.
arc- Jiffcrent
froln
in
tile
demons.
tllos~
of
Thesc
[Charni~k
"'~~ -:,;,,;!fi~~
72]
llccau:oc
prograr:l
:~~'
Hrc
cxecutes.
found,
it
tl,ey
the
lcft
dcf'lon
cre.,tecl
l!llen
and
tllo
C!(:ts,
and
destroyed
l1'.i:osinc.
the
;:.s the
propositions
deduction
;:rc
rCSUI1es
..:llere
off.
.~.
Tile
pror,ral1
can
Dsk
tl1C
user
for
thc
"
missing
.
,.
inforr!:"tion.
-
.
/I
III
-
.
this
ca:oe.
the
-
interecticn.
,)S
i
.
.
BI-::JIRECTIOJJAL
well
COI1PUT!..TIOt!
Ct~ the
Pal;c
in f c r c n c (!.
be c 0 r1e s b i
d i ~ c US S Cd i t. Se c t i 0 11 II. 2..
.
valucs
need
more
trigr.er
important
normD1
pro(',r.Jm
is
of
passivelY
J'\ n 0 Ce i nun
r;lissing
--
interaction
4.2:
it
tllat
can
C:1se from
another
information
is
n is:: i n C
user.
only
steps
progr~ms.
s
1'.
in
tt,e
out
ttlat
inforMation.
of
the
the
not"..
.-
F.\ / C s y s t em [ L e s sin f; F.1) \.1h i CII i s
it
ha~ choices
cor.1putation
the
the
.
it.
information
section
Tl1is
;lcquirine
;lcccptinG
~ t ion n 1
0f
of
data-driven
actively
a 11
questions
ones.
bounds
not
-d ire
needs
5imilDr
request
node).
it
forthcominB.
to
to
complete
tllose
l,resented
tllc
inforr:1ation
can
suspend
OJ" it"
can
a
in
(in
this
itself
heain
if
no
n new
cornputDtion.
An cxarnp1c
FiGure
tile
4. :1.
Three
situ~tion
Su~pE!nd.
of
bi-rJirE~ctional
ros~ibi1ities
where
or
Ask.
In
the
requested
for
r:iore
C'.r ~
II res
is
Dnd no inputs
input
C 11t
vullJes
sllspcnded
~re
iz
could
the
fi~urc.
wtlen
iJllows
t II t'
bc
for
QIJit.
two
",rc
lattcr
c!loicf:s
result
A request
t~:o of
~.CI) t
from
of
tt:e
is
the
ttir~e
user
input~
t ~llci r.l~ COt.":P 1 e t e con t r 0 1 UY
i rl (~l ud i n {~ res 0 u r Cc -1 i:1 i t. c:1 pro Ce ~ s i ri e
O:1C~ to
Q~ove
.
Ea c 11 c om po rl e n tis
wtJicll
ShO\ln in
not" cornplete:
\..hcn it5
present.
n"de
is
prcscntcd
\~ere
cc:1cu1ation
L!
The conputation
S!.OWI1.
com{Jutation
~llort
('X('cutcc
I" C sou r C <:~
n
!
cCJMIJut.,tiorls
in
Yl0 Cale
Ilurst~;.
d to
i t
to
finisll,
\:her;"
(f 0 r
(s e e 5 e c tic
lJut
cat;sez
cor:Jj:ut.:lticn
ins tan c e,
~I 2. 3) ,
Ion eel"
exh::lust:;
t i r1e c r
n u 1:1
Ue r
46.
I
-,
,4
~
,
,
J' f ' CTIO I"
' J A L C()I ' PU ~ ' 1' IC
o.
1,.
..
';T
: T
1:.1.-"-.1.\,
-o.
of calculaticns).
it
it
'
.
("ut;,t'
",
t:
{!cactivrlted.
'illerl
::Jure
':f
re~ourccs
-
C;qu~tion:
Input:
z
(x
=
requcst
user or
tlle
+
\1
for value
of
anotller
pDrt
back~Jard
z.
of
Rcquest
nClY be from
the systen.
. This
is
"-
corl;::onent.
IJot cnol,.l.';t! j,ita
is prcscnt
to ,IS~: the
u:;cr
fcr
inforrlation
to conJ}let.J
the
corn I; uta t i 0!1 .
It
i s s us p c n d e d. 1:1
Clkin (, i t
I(esult:
i1
for
..;~
x.
y.
Ag~in.
user
or the
proGram.
for \-1a r d I com po n e n t.
flesult:
""'C'"{
", ,-
cler:-lon.
values
Input:
y)
f!
Th('re is
cOMplctc
this
It
can
aIr-lost
enough
thc calculation.
data
a value
\l
request
bc froM
represcnts
';:~,-'
"
the
,c,~jJ::';;c::{~~~ ,~<:~:Y~;':
o"1:;;"~~j:;:,..,,,:;.:,'!;
, ,:!;",. "
:,:;c"':;"
"
.,~:...~
and
;;""t;,"'!~:- c ,:~~'
,oj"'c
complctc
tIle
user.
the
::::;
.
-
i;';"'
".: _:::'~J';~";o
-.
0"'"
'c'~-,;';'!:;c".j.;;"~.
present
to
so the vrorram
frOt1
~-
evaluation.
If the user cannot.
s ~ p P l)' a v iJ ] Ue. t I j e comJIuta t ion
r e f1a ins
suspcnded
.
CClfl
for
the
'..""
l;"iGurc
4.3
ColliJlutation
Pi-directional
--
' :':i;::',:-,-~';.'
.
Exc.:!l;Jle
.'::",:":_,,,,(~
-
-
":~~';',1;~
,,-"0
,"
i:rc
:1
l~rovidcd
for
it.
it
r;IDY continuc
executinl:;
fror:l
tl:e
0
~
I~oint
it
lcft
off.
Its
E:nVirOnlilent
\lill
have
been
savcd
in
:c';i,~
.~,jo
"c-
suspcndcc1 proccsses.
tliC
;:r,:
',,-(
,co:
(
II , ;. .
Con t r t] s t:;
Any or
I
iJ
~
."
;,ctt;urJ..
r;r::;:-II.
of
t.oc
rlocJ~:.:.
(~il.:Urc:
rer...(':.-:cr.tln;.:
~)i-(.lirec;tiontJl
\!!;ic!:
~.4:
I
,!
---
I
rcferrcd
fOI'.t'xa:1;J~(:.
,) ';)1-f!lrcc!.1o:::Jl
I
.
is
CClll be I'eprc~('!jted
;jctiOllS
to
sho\/S
Infcrencc
.:~
t1
:;tc:.tc-~p:,ce
,',"
an Ar~D-Cj{ ~rcpr!
t:xD!Jple u~ed
b:,'
ir.
,:;;¥:~
-"
,"
"":"1'
;,
;C':.'"
~
':
l'
:;
::
.
~
.
iJ1-D1RECT1UIJAL
[I:artin:;
tI,e
COrl{'(;T1\11O::
'.:1]).
t',raph
ncl\/ork
is
for
P\.l;~(,
1:0<.'(;:; rCI)r~~;ent
for
hi-directional
;...nd rulc~
inference.
bi-oircction"l
intermediate
propositions
:;eo:rcll
or
Tile
if
nod!:::
cor:!putation
4[
irl
.1
rCprCSE:llt
steps.
II 1
I ~ri
J
/
':
f,l;
R2
.'
.
ii2
j
.
i'ocic~ labeled
,
,
11~..
:15
:'
.
"f"x"
tho ~ c 1 a b E'led"
~,'t;l~;;;~~:lt~'c~~~
{'.
re pre~ent
Prc position-x
r e pre s c n t
r u1e
""
1-;x"
~,.:&::\""
::'~,~~;~:t";:;:~~:;:
"'\ c"',
,,~,';1~~
.
-x .
-",i;C'c:':'!",;;c,;,?,;,(
--
I;
I~
. .c'"'i~;r~.~
fl(,
'!~~:~8
Fitiurc
-
An 11f;L'-Olf
for
I! ~ c h (I f
the
b i-Ii
of
~cckinr;
~
j;<11.ll
tllouCI!t
a~;
of
az
~~i-directionCil
'" ,:,
Scarcp
--
TI;c
.!~
. 11
throu:I
..
a net~:ork
.
tt;e"
all.
J
j,
'.ot
:~;:;k;~
ctin
~
)':c;",:-;~!c
.i4"~:.
searc!.
t~cllniqlJcs.
;~\,;
i r c c t ion a 1. s t rat c L i c z c:'r"n b e
~cC1rcll.
Ui-<.!irectionDl
thrc:c
4.11,,~;~
::artins's
nc c c;U3 C
thou~ht
bc
Gr~pll
i:.
tnc
initi~l
':lost
(Jlld
re:;trictcd
~oal
of
zt;:.te5
must
.;;~
t~':e
},::+
~e
';;:
"'~'"
'+'1j:
kno\:n
CXtJlicitly
'olticn
tilt.:
3ec;rC;!
u~l~ins
[D'~(:I:c:mrenUX
7",'.
,!;'
"""~
Pon!11].
palli:;
"i"he
i~
:.ec:rcl:
~ucc:cssful
\JhCTI
tliE'
t\IO
:;c~rct.
intcr~ccl.
Ilultiple
~tC1rt
ant!
i;o~l
5tatcs
3rc.:
possible
in
~
'h
'C~
~
t~
,
ui-<lireclionfil
inCcrenc(..
"II
rcllr~se!1tillf;
-,.
nodt"~
c"3~;ert.~c!
)
,
.,!~
or
:..~~
,:~;~,,~;"J"i!
.
:~
...
.
.
I.I-VIRECTIOrJftL
qucricd
by
CliiiJ;'JT,,\TIC::
for'.J::JrcJ
do not
Thcy
'.Jr !JCJ'.:i;wilrd
r~pre5cnt
Rntllcr,
tlley
instead
of
c:r~
tile
P~l;~
irlferen(!<:,
~C:t:arc;tc
dynill:lic
~in2lc
stiitcs
of
initii'll
~scd
in
statc
ncets
tile
frontier
i n f Eo'
r e n Ce s can
by
tile
IOU:}
tlultiple
-.
com
output-lJriven,
nny
:icarch
of
.Jsit
one goal
i::; in
[;ro\/in(;
(1n)' st~rt
from
a Goal
CDll
states
nay
De c a use
to
~
beco!le:3
to
functions
rRIljT
or:(; of
!iicIJ
mlJ3t
bc
output
trcc
t'IC
U:;C.
1.;;,,<: furthcr
to
cor.ijilctcd
tlJ,-t
tllat
statc
sc~;rcti
3tate."
::etl
s 1 t u C1
t ion
also
c rea t e d
exist
b a c I: w ~ r d
initiates
the
nodes.
goal
take
f~:;~~~~t:,~
'.
a t Ion
1 s
c,.',:':~~~:~.~C
:~;~~'t,'~"';:;;?'
':;:"4:~('
.~~;.
~;,,;;;(..
:;;~"
... '"c"_:'j"' " '
t-,1;:""
.
rcpresent
input
c.
,.~¥. ,.!i,';":';~~'.;;~~~
irl
co r:Jput
function
is
TII~
it
of
not
\)f
duta
<l:ftCi
is
u~e.
,I
tree
.
t!l~t
inr,ut
flo\.'
tJI(.'
n('!~urc
n!.;cf.'s:"Jar'j
Tllis
:;Uf:l~"~"'S
r-:--
one
the
searcll
initial
nocJc,
:3tate
r;j(!ctinC::.
t:iat
printeC.
:;oa!
IJ}' thnt
forl/.1rd
ull
d'ita
[ort:arG
t.'
fron
pat';
c.:Jn be
of
for
search
valuc
rcj')re:;Crltcd
:10t
./hen
of
the
initial
~r;
a
rt;prc:3entinG
De c a u ~ c C3 Ch Go a 1 :3tat
I,c ~rint.ed,
so
node3
satisfied
1~leets tilE: scarch
:;c('!r(:~j
in~i(;ate~
C:I
thc
t II e i 11r ere n c c c" s e
..n
The
ir;ipliC!s
"The
f 1 e c tin it the
.
r. u t C1t Ion.
COr:1I-'utntior!
rcprC:3ent~
found
~1) reports,
frol;;
nn~I :;oal
throu311
bi-cirectional
C,IC!I
.-
statc:3.
The search
trcc::
used
_: --~~:::.
and
c,"ll:3
initial
[ro.:in:~
initi.::l
~ir"iJarly,
nod~-"
one.
.
0
b 1 - d i r c c t 1 0 n a 1
bncl:\/ard
~oal
n~tt/orl.:.
-- ---
frontier
the n be T;I",d ere
0
prey
th<:
arid
thc
classical.
/:s r.r;:a,rtin~
i:3 succcssful--!-lhenf:ve:r
throur,l-:
- -.
-
bi-directiona_L:;~c"rch.
rc::I;cctivcly.
.'iearcllcs
:;ct:-.
4~4.
Sti!tC
i,as
coMr:'utation
or
resul
Scarcn
t:;,
trccs_-
to
",,;;i'.~J~oili~~lf'
.,
.
~
CI-ijIllECTIO!;AL
rll..I?U not
connec:t
.j:J:..umption
on
Goals
set)
it
COI.:PUTATIOrl
tllut
set
by
rcquires
iz
\;itll
Goals
exist.
Effect
--
on
f"or\/:lrc.!
the
UaCI~~/(ird
[Ill
the
sc:c'!rcil
tree
searcr
(it
not
to
Boals
l:fJve
zearch.
sf?arcI1e:.
focus'
l-ccn
unlcs~~
If
are
~O
the
be undertCi~:en
;J backward
for\..ard
Ilo\-It"vcr.
rcztrictcd
lIe
coMponent
of
possible
trC':c:;.
col:1J.oncllt
fOr\lard
C!
at
tIle
bucl..\/ard
the
that
directed
Pafie
no
c:llo\/ed.
~PC I:odel
/1.5 di3cll~seu
thus
fiJr,
production
in
the
is
SPc Model
,
uni-drcctional,
prczcncc
tllst
of
product.
-
(:at~
-d ire
of
it
can
Tllis
triecerz
ir:!:!ediately.
or
Si1I'ie proccss.
CI supplier
A producer
c;rc
CY.I.) icitl'j
.
tile
The
to
uct
rc-1ur-:;ts
\!!Iich
a bi
to
~Iicl;t
for
rec(
;Jctin!~
irl
ivcs
lilc
at
Uti
Ilave
t. h e
some POillt).
pro d u c e r .
order
froM
Lo
tht'
\.,ill
i('s
tllrOui~li
is
rcacllC"":.
1::'CCiU~C
it
tllis
~Dck-c:)t!in
:!)i~llt
!lccds.
tho:;c
tliell
It.s
a
..
del i v e r t' c.'
(!irf;c:tiorl
r('cilJC:!31.. thc
r.,.st
of tllc
I),~rts
,~uppli(:r~
woUlri
tllell
lit..' c.!emcnd
of
0f
for
on :Iand
;:;or:1C :;uppl
a
COI!1putfJtion.
to
SuPi:lies
t'or'\:arl!
ideas
by 'un
suppliers
Ut'
tile
a
nIl
llack\-/ard
tile
by
for
- d i r (\ c t i 0:1Cs1
stilrtcd
!JC
1~(:5 I..llc l'(irts
\/!IO
t 11u t
,3S procJucer~
'fh 0 S e par t 5 r.1i e h t
supr].ier~
in
the
( Rerr: e I,)b e r
rcpre~cnts
re(juest.~
eithcr
Ci COrlSur:lcr
incorl'orate
uct
C:1n
rcqucst
[t p pro p r i ~ t e p C1
rt ~
:;Ulil:lierz
syster-.
SPC sy~tc~
consumer.
ordcr
thc
trif~r;cred
from
producer
t 11e ,1c t i v i t i (~s 0 f
An inactive
01.llcr
CCin be
a reCIucst
the
r:!ode,
Lo 0 kat
urll..il
it
c t ion (I 1 c "~I put ~ t ion.
corl(Jonents
The
by
Uy allowinG
rnultiproccssin~
bi
~r
is.
~
.
."
DI-DIRECTIONAL
Tn f'
of
:; y :>t
suppli(~s
ha~
no
COI":PUrI..TIOfl
~!;)'5
to
to
an
"oriGin;"!l"
requests
inside
any
for
and
tllc
be
~
allowed
cannot
be
oriGinal
for
any
of
for
any
nurnber
processes
the
Di-directional
coclputation,
u s c r 's
wi tll
tille,
nee d 5
I!lore
tllan
.,nd
pro d u c t
.
for
r~quests
parts
/
parts
or
demons,
can
All
of
on
and
these
.1
til,e,
number
of
etc.
likc
a ~y~tem
conSUl:lcr
based
proccsscs
arrivcd,
usinr
to
more
sensitivc
roc c s ~ i n l~,
und
supplies
be
bi-<Jirectional
I;lore
can
tllan
be
r e que s t s \l h i c h Ii ~1V e bee n 1:1
ad e .
I
ii
required
Ilave
products.
schelne
supplies,
for
linitinG
production
sif"!ultancously,
n y u sin C I~iU1 tip
one
by
suspensions,
"..hose
production,
.,110t,,3
the
.
by
c;'Jn initiate
r~quests
of
bc
of
then
created
or
can
abs(:nce
set,
are
~llil;l;
tirle.
processinG
amount
been
cnc
supplies
the
producer,
Tllese
be active
rescurce-limj.tcd
in
have
sub-r,roducts
can
workers,
each
producer
of
These
processes
a later
is,
c t e G t 0 ~1a r d .t hem
obtained.
'at
rcactivatcd
The
i 3 d ire
production
resources
wllich
goals
i C'.t e c b y i n rJlJt
tllat
systen.
productions
If
for tl a r d pr 0 d u c t ion
proouccr.
thc
all
parts.
Suspcndcd
.1i ~0 be i nit
3 Ct i v i tie s can
supplicrs
applied
Pc1CC 51
to
a. l-'rod u c e r
one
focussed
suppl
(';
can
ier
to\l'clrd
dea1
at
the
8
-
.
Pa c e t;2
c""""
f'"
oJu..I"rl"
~
..
~.
SUjll:Jl.RY
p;) i r:3 0 f
for
\: iI rd.
tJ ,I C I: \..rJr d
discusscd.
are
co 11t r c 1 a 1'1
~.: in f <:r c n c c ~;t r i) t Ci: i e ~.
TI:e inference
11c.nifestations
For\/ard
of
dati:;
irl!:JcdiutelY
Cilld data
The
backward
to
co!:Jput;:;tion.
r CI; r t' 5 Cn t ~ d by
.c v..1 u Dt ion:3.
wait
Ui -d ire
for
1:1C3I:cup
wtlic}1
evuluntion.
to
~:cre
all
I;ossiblc.
Group
before
is
perforr:;inG
c 1 uo e b i -d i r c c tic
inferl:IICe.
.,11 of
ion s tor
e d u c t'
strategies.
irltroc:u~ed
These
involvcs
differ
jlCJrallcli5m
wllich
the
~ D1
cornlline
n U::1b c r
static
i
0r
to
in
add
two
;an~ o'loi~s
anc1 eat;cr
Clllother
~/ays:
dir:ension
ear;er
unnecessary
~Ji11
~;OI1(; 1::lnCcr':o.~;ary
i,:..
r OI"'
('
r
,,v,,'I.~,lJ
<
'&-"
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.,
'
au
I""" ""
r::odel
t:.:.e:3 I:rcduction
d'"t.:1-rC(!U<l~t
~t
c;11 tJn d
work.
(~;I'C)
j"!ie
the
Col!1putations.
c V r. 1 u ::1t i () t I j II vol v ';; s n 0 pur" 11 f: 1 ism
I)Cr[orm
tc
evaluation
\1h i 1 c ~ t n tic
<lc:t~-cnt..r}'
[or\.;'irl:.!
use
extent
data-request
c t i 0:1 a 1 "c t ion sin
control
cprililarisons.
introdllccJ.
r:".ir
required.
Two otller
In
eacll
tllc
acts
erc;:;test
c1 rcquest
for \. a r d ~ n d b a c k \-1a r d 0 P c rat
calculations
in
f c r e n c e ~ n d 1 ~ z y e v [! 1 u a t ion.
and bi-'Jircction~.l
sc'drch.
the
or
b a c k ~Ia r din
tccllniqucs
flo\1
Group.
and
5cllCI:ICS
5C1me idea.
01" datu-entry
new
(~
c t ion :11 t c c :! n i q u CS \Je r c
And control
the
i(jfercnce
Col:lputation.
These
-() ire
bi
;JrI d
r c r r L ~ (; :"1tin
l~or:1l)utations.
tlJC
of
cor:putatiO:i
to
r(.pr(:'~Cr1t
LI~(:
~cqui~ition
.1,15
to
-
I
~
,
.
U
... """"'
.;> ",'/\11
Y
Pan" '-
ra:'r('.~ellt
and static
eaGer
cilcll
t.cctlniquc
discu:;scd.
evl:Jluation.
i1ncl it.:;
Cor.lbin~tions
d~scribed
to
sito...
thc
J~:O~Itile
rcspcctive
Wus di~cussecl
usinr
for war d and
to
enable
search
space
overiJll
of
use
arid
rcsource-linitcC:
togethc-r
a computation.
bi-directional
tJlroui';l,
ev(.;]uatiorls
pro I" r Din q u cry
~as
which
could
the
u ~c r
Spi1ce;
rIot
for
the
u1 t
r,nd
SPC modcl.
irltroduccd
cut
to
down
tllc
,,;erc
to
i3llo\J
dcmons,
complete;
/" is sin Gin
i1nd
0f
t.cchniques
ShO\1
s c lie 101
c s co u 1 d be
computation
senrcll
I
in
\!erC'
a producer
Tit ere:;
infcr(';nce
A/nons
pro(:cssin~,
the
und
of
.
\;as
acquisition
operation
combinations
work
Inodcl
and
i s aft' e c t c (I
computation
ta'
for
search
in
prorJuction
b a c k war d com IJu t i3t ion
them
CJrI tllc
control
tile
I3i-directional
(Jffect
of
r ('.p r c s en tin g a corn}JIJ t c! t ion
co~binin~
-'J
r.o:
the
110W
COinbin e d
size
devices
of
thc
sug[,c~tcd
Multiprocc:ssinc
a brea(;tll-fir~t
to
handle
11.:lvinl~
tile
fur 1:1
i1t i Qn .
I
i
i
I
.
'"
-
t
6.
-
(
'
-
'I'~
-
,
liE".Efil-~!!Cf:S
1.
Arvind,
in
at
2.
3.
--
F"..
"C"
I ~"'~""'
I:... .. 1\.. " CE ;.)
('
,- -
Gostelo:i,
~:. Plouffc
Data Flo::
TR 69.
Lc1:~[.uae(:",
}:.P.
c: Viablc
Irvine,
l~a~:er,
If.C.
G;)rt.;~r;('
1~
f'.
-5..'
(.;,
Coll(~ctinn
(
"T G" R1'
..."
u.4
3nd C.
111.'\!itt
of
(197(,),
Univf:rsity
(1977)
"The
'ProcE.c;5(.:;,"
in
"Pro~rar:1nin.~
of C~li forrii~
Ir;cre~cnt~l
cor:lbinc.-d
.':!GPLAI~
Dl~c:., F. (1 YuC,), "I, iiE;di.:ctivC! Cuestion-J'\ns,,"crinl~
Sy~te!~,tl in ~£.~~
:r.for:-:ation
PrOC\!SSille. ::. r:insky
'(ed),
tilT Press, Ca::I'.">rid~e. I!l...
4.
Bobrow, t. G., Rapllael.
t.1. (1974) "I!e\.. ProBral::r:inr..
Lanr;ua~cs 'for l'.rtificic:J1
Intf.'lliecflcc
r~C!scarcll,"
~£.!:!..e.uting ~:urv(~y~, ~, 3.
5.
Cllarniak,
E. (19rfGa),
"Inferencc
.and Kno\.f1edCt' I,"
Co~I;utational
~erlantics,
E. Charniak
and Y. \':ll~;s
Ted:.),
IJortli-l:ol1i:.nd
Pu!>lis!.inc.
Co., pp 1-22.
in
6.
Charnia~:,
E. (197(fb),
"Infcrcnce
and r.no\o/lcd6c
II"
COI:1J~utati()n(11 ~crnantics.
r~. Cllarniak
and Y. 11il~;s
TedS):t-;orth-lrollnn~~-PUuli:lllinc
Co." pp 129-154.
in
'f.
Cllarrli..k,
E.
(1972),
!ITo\,~.rcj;j
~tory
Co!.'1prctiension."
Lauoratory
TR-2G6.
8.
\) .
10.
1 ...
?
ClliJdrcn'z
r;IT
-
t",I
"J\n Cvervic;w
of
University
AI i:e~o
C:71.
Den n is.
J. n . (1 c:7 9 (I), "111f.' Va r i e tic ~~ 0 f Dat a fl 0 \1
Cor'1puters",
"Procf...edincs
of t!le first
International
~~~(:nce
on Dl~;trullutivc
Co:'1puter
Zystcr1s",
IEEE.
Dcnr;is,
I.
.
of
r'r:D cjjssertation,
Davis,
1<. and J. .~ing (19i5),
Procluctio!1
:':'ystCITIS," .;tr:nford
J.r:..
f\lr.(~ritI1I1ic
'~ 11 ' LC'f'
11D
I:odcl
,.,
n
'
" 1 (,.
1"
t'.
UX
'
';',<Aii,"""',-,."",
l:il:ircction"l
t "
" C"t
"J'
~~~~.
~,
I.rlCI,I.J:~n.
,
0,
"Vi,L
Lo";nr:;l\For~.
r r,!..
C' I .""r",~'
(197911).
.'
n"
.Jnt: '
Ii Vul\J(~-o:"icntc:ri
Prelil~inClry
L
-, li(~urj;;ti(;.
'..
L''. I' .
--
~.~.,'"
"' lo r'"
""' n ..:"
TI"' >rC\ "".. (:
f,ll~()ritllll."
J()urrj~1
--
'\ lCJ"{() j.
l~v(lluatc~ its
i.ri:url(nt~."
i:1:'.
«:cI:;) , j:;.utor:tala. .!::~~::e5
ur;~
".
vfllVf'rSl
ot
y Prt:s~,
/
I
/
"I"
..,r.ln';.irC,i.
f
J,iJnufi1",
C
.I'"77)
'. (l
~'carcl;
f":'~C
};efcrcnce
loP
tI
COriS
,-,.IOU.
'I
I
IJiclJDcl-;-O:;-Dnd
Pr()~~~~,
~r:~"fIJf
C:)(-£'<"'.
'"
of
r.()
' l
1-:. ;:ilrlcr
[c! ir.l"urr,ll
:1
--~
1
"
;.
.
~1:.r-EI,.:..;C.:..,
:~;y'~:
'.
,
~;:;~~;~~~:c :C"c
.. . . r.'
c~£lt!i!
-"
-
.
"'ijY~\,'"",,,.'
I"C"
P"Cc
x:'
.-fr;of""
13.
.
.
'"'
1'1.
lie witt
, C. (\1~71)
PLAJ!IJER",
Confcrence
!"'
15.
.$
:J.I
::;:~,:~
li..yes,
J.I'.
(1~7f;),
C;orlliutcr
l.rcl:itccturc
" 11 ,
Inc
Or r:a n 1. Z OJt.;.1 011 , I .t'i cur ~ \1- 111
,'-
,
-~~
"i'roccdurCll
i'lld
l':I:JI'l.'cldirIC of
Procccdinr:s
of thc
on l.I,
V 167-1f.2.
':'C;t~11
'
:'~ccond
1"
l:nowlc.GGc
Intcrnationcjl
'°,
Joint
c
:;~~jj;:;;t;,
iii,
",I
:
""c:':~
f,c ':,,-'~;i
Ilc\litt,
C. (19(,9),
"PLANJ!ER: {, Lan{;uagc
for
rrovif'.~
Theorcr:Js in Robots,"
Proceedin~s
of the 'First
In t err. uti 0 n a 1 J 0 i n t Con f c r e n c con
f.r t i f i cia 1
- - InteJliBencc.
pp 295
301.
')~':::,
-
,".
I
16.
Jdrr.on
filri,
"
;if
:~~~~;,
17.
GL~;;Jf.I~G()r:,
on r:ACSY::A at. liIT.
t:CJp)an,
;;~;';'".
;';::'~,i;~~:,',,~::
R.li.,'
(1973),
rIatur~l
Lungu~:&c,"
Conferencc,
1973,
s,,~::;..;~~ '-j"~c;;
~~'.~~,,~J~.."
(1979), 'file
-
18.
-
'
cooperative
Trnnsactions
1, pp (,;1-1)6.
on
D.L.
(19C1),
distributed
Sy~teMs,
I:an
19.
Leun~,
C.l:.C.
(1975),
"formal
Data Flo\J Schel:1us" t, 11AC TI166,
20.
Mnrtins,
J.,
D.P. I~ct~ay,
"l\i-dircctional
Infcrcnce,"
Yorl: nt l~uffaJo,
Tc('llnic~l
--
Approach
to
r;ational
COI,I(Jute
"1\ riulti-processine
I'rocecdin
s of the
pp ~3~-~40.
V.J(. und Corl:ill,
accurate,
:;,'~i':~~
IrIFGrl.lati()TI
I
Lessin!.;,
"j,~.ii:'::
on-line
;
"Fun~tion;lllY
systeMs",IEEE
And
Cybcrnctics,
PrOl)erti<1s
lilT.
.
Sr~C-1
of
1,
\:ell-forlned
S.C.
Shapiro
(1981),
~tAte
Univcrsity
Rcport
171;.
of
r:~\1
:,
21.
r;C(jri1\I,
J.R.
(11)19),
"Dota
I-'low ConJ.,utin(~:
:'~ort;.\:;ar(.
Devclopillent,"
rroc(~cdincs
of tile r'ir~t
International
Conference
on Distributive
Conputcr
:';ysterTIs,
lEEr-:-
22.
l:cl:~IY,}).
nnd ::.C. ;.II"piro
(l~(;O),
"I!ULTI,
i:; LISP :'::.I~e
!~ultiprocessinl':
.c:'.YE.tern,'t irl Col1fercnce
t;ccord
of tl;c
..!.lli
LISP Confcrcncc,
pp 29-31.
23.
IJicllol~on,
T.
(lC)(,(),
Dctw<1cn
PI' 215-80. T~JO Point:.
"):-indin(~
ill
ttle
a 1:~t\/ork,"
2't.
IJilsson, Pu!)lishinr:
I:. (19CO),Cc'. l'rincip1es
Tiol:C:
2~.
PoI11,
of
':tlortest
!-.oute
-Computer
Journal,
-
Artificial
Intclli-
;
-9,
~e
,
I.
(1971),
L.
.!nt(:lli~encct
'-
2t.
E15cvicr
I!rltzcr,
Puhli~hinr.
Co.
D.
Inc.,
Pohl,
1. (19(,9),
""Ii-'.lirl.'cticllPl
in r',1tll
Problc;I.1~t't
::.L,'C rcport
I
;
~
tlli-lJirection:Jl
--
::;(~ilrc!I,tl
:~ic!lic
pp
in
(t'dz),
1:;Jc!lin(:
/,rieri.cC1n
1:~7-14(:.
:'.,;-
.,.
~#r."':i""';:'"
;:\ 'c-~~.;;.
..';."" ,
f,i,'~:..':':i';
"";c~,.~~t,(:it
C!rll.! l!l'uristic
~;e~rct.
r:o.
10lf,
~~t(lnford
CA.
')
'.~;:\~',AJ"
~1";'
,;';,.~""-",.,,
..':,;
-=
:~~:s:~~:
:~i;;'.;';::;:~:;
-~
-,:.~,~~!i~~(,.c
;(~..::,."
~~.;c_._~,
,
,
I
.
REf E f; E rsCF:~
Fa C~ :-!:
d'
Pratt,
27.
1'.
-f'rOr;r:1Mr:',in[, -
(l~'r~),
.!rlpler:-:entation,
.213.
keiGer,
Lani~lIc;'.(':;:
..~ -
Prc:lticc-iJ(lll,
C.
(Ind
';:r:!cll] ,
Inc.,
=.~. (191~1),
di~tributed
word
eXfJert
natural
II~EE Tran5actiorls
on Syster:Js,
SHC-11,
1, PP :j3 -- '31.
Dcsicrl
~
-
;!nd
-
1Cj7'j.
"To,J;lr(j
larll:unzc
11an t.nl!
of
a tllcory
parsil1{.;"
,
Cyoernetics,
29.
SIIC1piro,
::;.C. (1981:3),
"COCCI:
I: Decluc.tivc
Semantic
JZct\Jork Proi~ran
for :';olving
r.jicrobiolor;y
Unl:nowns",
S U!l Y 13
u f fa loT R 113.
-
30.
SIJapiro,
S.C.
(1981b),
"SNePS User's
31.
Shapiro,~.
C.,
ProcessinG
findler
32.
and
Thc Sl1cPS Ir:lple:Mentation
(1979),
Syztcl:1,"
(ed),
11nnunl",
hcadcmlc
in
.
"TIle
Sllef'~
Associative
=
Press,
33.
Sc:'1~ntic
pp
rl.
v.
179-203.
Procr.JM
-
::etwork
r:et\...orks,
Inc.,
Sharp,
J. (19::!.n),
"/');1ta
Crientcd
S I GPL A IJ, .!2. '
, p p lI" 51.
<;'
Group
i$uffalo..
~UI;Y ~t
Desil~n,II
Smith,fI.G.
and D,IVi~, ri. (1981),
"frC1Mcworl~s for
coojJcration
in distributed
problem solvinG",
lEEr
Tr;Jnsnctions
on ::;yztc:rrIS, Ilan t.nd Cybernetics,
.';liC-1.1,
1, pp 61 -- 10.
.3'1.
StallMan,
II.r:, .:Jnd (;.J. Sussman (1977),
"ProbleM
SolvinG 1'.hout ElectriccJl
Systel:1s," Artificial
1!:! tell i ~ e n £~ ' .2' 2. . PJJ 1 3? 1 9 6
... ~
-
35..
Steels,
No.1,
36.
Steels,
1.. (19CO),
"Tile
SchlulnbcrGer-Doll
L. (1979),
Cor:lrnullicatine
31.
Sussl1an, G.J.,
II
38.
rlIT
:1achine,"
iiicBef1Cld,
110dclcd as a Society
AI Labor~tory
of
TR-5l12.
T. \.Iinor;rad and E. CharnicJk (1971),
-
I/ccllr~iv(~
(197~),"~tre;)I'1-oricnt~\!
D~t~
"'lo\J
::;cllcr-1as,"
r1AC
;'.c a c!c mi cPr
e 5S.
CO::1Put~tion
Tect.nicnl
l:eno
in
/':0.
G8, I1I1.
40.
41.
.
1/i1~:.:-;, Y. (l~'i'(,)
"f';:r::irll::
Enl~lisil
II,"
in CorJputatioriul
~C~lcjl1t.i(;s,
L. Char-lii;,I:
;:n<l Y. \:ilks
(C(~s),Nortt:-liol1and
r'ubli:;!iini.:
(;0.,
pp 1~5-1r.4.
\!ilk3,
Y. (1975),"1,
I'rcfercl1tial,
~c::I.;:tics
for ;:.1t.ur.,!
L.,r'G!lagc
In t c 11 i ,~
e
n
c
e
,I
6,
p
~~
~
3-., II.
"
,
I
i
.
and F. IJaycs-Roth (197R),
dIn r e r ~ n c e Sy s t e r~:;,
-Pat t ern - Di r c c l (:--~--
\Jcn~, r:.-:j.,
.
I1I r:er.lo
CT.
ri i c r 0 PLAtill El\ I~e fer c n cell an u a 1 ," Ii I T AIRe po r t 203 A
\-Iaterman, D.A.,
3!J.
-
~
Constraint
Research,
"I(e.,tsoning
Experts,"
.
..
P:lttern-sce!~irJr;
Infcrcnce,"
4"1rtifici;Jl
--
.