Research R.port 276
Agency and Autonomy:
A Formal
Framework
Michael Luck and Mark d'Inverno
RR276
With the recent rapid growth of interest in Multi-Agent Svstems, both in artificial intelligence and
software engineering has come an asscrciated difficulty concerning basic terms and concepts. In
particular, the tem-rs agency and autortotry- are used with increasing freciuency to denote
different notions with different connotations. In this paper we lay the foundations for a
principled theory of agency and autonomy, and specify the relationship between thenr. Using the
Z speciftcation
language, we describe a three-tiered hierarchy comprising objects, agents and
autonomous agents where agents are viewed as objects uith goals, and autonomous agents are
agents with mot
i
v
a
tio n.s.
Depaflrnent of Computer Science
University of Warwick
Covenrry CV4 7 AL
United Kingdom
December 1994
.\gen('\- alrti Atttot tott tv: A Forrntrl Fr:rtncwot'li
Mark d'Inverno
Michael Luck
Dept. of
Corrtputel Scieucc
v of \\Ialu'icii
Covcntl1', CV4 7AL
Unitecl Kingrlom
L]-nivt:r'si
t
l]l'r.q.tl. mikeluck@dcs . narwick.
'l'ar +44 1203 523193
frax +44 1203 52il7Il
ac . uk
Sr;hool of Courprttel S<'iertce
L-nir-t,rsitr- of \\, r:stmirrst t'r'
Neu' Cavendish Stlcet. Louclorr
LIrritecl Kingclorn
I,ltl'r,q.lt. di-nverm@westminster. ac ' uk
'I'rr
+4,1 171 911 5000
Abstract
in NrlrrlriAgcnt Slslt'rrls, l>otlr irr ;r11 ificial
irrtelcsl,
glontlt
of
\\,i1lr thc recctrr laltitl
au associ:ttt'cl tlifEcrrll,y cottcctnittg lrasi'
cottrt:
lias
iltt:lligelcc ancl softn'a.r't'eugiueclirrg
(L!Jen.:lJ
atrcl atllr.,ttotl?y ilfe rrst'tl rr'illr i,,
tlrr:
tt't'ttts
parlicrrlar.
tt:r'r1s 11cl copcepls. Irr
cotitrot;t1iotls. ltt tlris llapcl'
<liffcrent
rl'ith
ious
nol
<liffelcnt
cr.ttrsilg fl'ecluerrcl to clenolc
alttottotlt.r'. atttl :l)cci[-\ tll('
atttl
agt'ltcl
of
thcrit't'
rvc la-l' llte forrlclati6us fo1 a ltlinciltlctl
t'e rlt'sct'ilrt'ii lhlec-1it'r't'tl
larrguagc,
Z
spec.ificat,iort
tht
lelationslrip llctrvee.1 tlrerl. l'sing
:l8,culs;rl' \l('\\'P(l ils
lr']tere
agcllts
atttottotilotls
ancl
Iierarclil' comptising olt.lects, agents
irtr.,/lloliotts.
u-i1
li
itgellts
are
agt'lt1s
olt.jects rvil lt .qoal.s. ancl arrtonorrrorrs
Introduction
1.1 Backglound
A1t1L,1glL thelc has lreel sultstarLtial ltroglc'ss irL artificial irLtclligcrttt' for'lIIillI\-\'('lr1\. Ir'sr':r]{ ll
()1 f. t1L"
tcrrric<l t11 lecrrs t-rn soh-ing lllolrlcrus u,ithout legalcl to 1111\'r'ea1 t'xtclrLal t'rLvilorLrt,('lIt
sigrLi{i(rrLt
u'lLilt'
nrtiol 61 a rcasorLirtg o,r1ent.. hL ollLcl ri'olrls. the prriblerrrs artrl tht'il solutittns.
*,ert'liuriteci in that tirev rvere clivorce<1 fi'orrr leal situations. X'{oIe lccentll'. ho$eY.L. tlL.
irupoLtalcrg of these linitations has been lccogrtised. One conscrluell.(o is the titlticl glorvtlt of
intelest i1 tlLe clcsigl ancl constnr.ction of o.qent,s as s\-stelfls exhibiting iltclligcnt l-iehaviorir"
Corrcelrts cf ct4ents and ogency alc- ilr:r'easinglv being usecl in a I'al]!lo of al'eas of at'tificial
i'tclligcrrce (AI) anrl cornputer scienct:. However, thttse nrltiolls al'e olten tliffelerLt. cvt'rL
rvithin thc samg subficlcl. aucl tlLe lac1i of a colllrnon unclerstan<liug can stifle furtlLt'r les''at, lL
a'<1 cltrr.qloprrrelt. In rlistributed AI. aqents are oftelr ta,lien to lte the sal[('as o,rt,futrnrtY)\ts
t'eler-attcc rlr'
,"r1e:r-tts, alcl the trvo tclrns ale usc'cl irrter<:hangcablr'. rvithout lega,r'tl to tlLeiI
sig'ifica'ce. The iliffercuce betu,cr:n tht:se rt:la,ted but distinct notiorLs is lioth irLLliortarlt ;rrrrl
useful irr consiclering aspects of intelligclce.
In tlris paper. we clcfi.ne autonomA arrd agency, and explicate the relationship lietween theru'
\Vq 1rgne t[at autouomy is rlistirLct anrl is a,clLievecl by nt'cttiurtt'in'g a,ge:ncy' Out conr:eLn is to
clevelop a, folnal model of agency and a,utonomy that can be useil both as the llasis ol arL
irlplelreltatiol, a1d also as a precise but general fraruework for furtlLel tt'sealr:lL.
1.2 Benevolence and Autonomy
In tra<litioual nrtttlels of goal arloption. goals ar'c lloarlcast liv onc. agellt. arrrl at6'tct1 lxothel agents ar:colcling to their orvrr reler-ant colrlrctcrLcc [18] . This asslrlues that agcrrts
:rlc ah't'at1r'clcsigned rvitlt comrttoll oL 1to11-('onflictirLg goals that allo1, nutlal trs.rstarL.c rrr
satislving adrlitional goa1s. NegotiatiotL its to lLorv tlLcse a<lriitiorLal goals a1e sltisficrl tr.''ica11,
talics the forni of urele goal notlc aliot'trtiou. Thus irn irgcnt sirnplv has to t'6prr.uurr,;r t. its
goal to arrotlrcl a,gclt. ancl cooPeratiorL ri'i11 e1rs11o. TlLis corLcept of ltt:rtr ttctlrtt,t otlr:rt,t.s
III)
s'ho corlPt:rate rvith othcl agents n'lLetter.-c'r'anc1 rvhelever possiltlc. ser.crslr'corLstr.airLs tlrt,
I'it'lLrLtlss of llclLavirtru that t:art be a<'hieve<l b'u'autouorrrous agents. ltv viltue of its sir,lrlisti<.
arr<l liilrite<1 r'iet' of tlte rvor'1r1. -{rL autonomous agelrt nra,v cxhiltit betLeyolerrt 5r'har-i'*r'. l'rt
a 1ltlrel1'artcl exclusively irene'u.cilcnt agcnt is not autonornons [-tr] . Coopc'r.atiorL n-i1l 6<.<.1r.
Jlql11:1'p11 trvo agcnts onh'rvherL it is considelcrl arlr'antagcous to eac:h. Arrt6nor'ors a9(,1Lts
are th11s self-itrtclestecl a.gertts. In this vieu,. autcirr()ltlor1s bencvolerLt bt:har-iorrr is possi|1r,.
lltt alist's ottlr- tltlortgh thc self irlterests oi arL agerLt. -{ goal (rvhethcl viuri.crl as 'sclfisl' 6r.
'alttuistic') rvi11 ahvavs be adoptecl so as to satisfv a self-intelcsteri rnotivation
[1].
As stirtctl abovc. the tcrrtrs o.qertt. arLrl (ulcrL(:'!J are rrscrl tc-r <lenotc cliff'elc'rLt ,',,11 r'pts. Clir-t'1
tlt<l larL,qc of atcas itt u'hitrlL the tclrtrs alc appiic<1. tlLis lack of corLscnsrls olcL rlt,lrrLirLr is rL'rsrrr'lrlisirrg. -{s Shoharu [13] points out. the rLurnber ofclivelse uscs ol the tcruL o.r1r:rtt ;ryt's6
trtarLY tltat it is almost ntcaningiess s'it1Lout 1'ei('1cnce to a palticrrlal notirtrL of agcrLthotirl.
Irt a t'ccclt collt'<'tiou clf papols. {bl cxaurple'. scvclal diflcrerrt viel.s crnclgc. For Srriith 1171
att itgcrLt is a "pelsistt'rLt softrvalc eutitv clc.clicatctl to a specific p111 pos('.' St'llict' lll] talics
agcrtts to llc "cotrtpiltcl'p1'oglams that simtrlatc a hrrrrLiin lelatiolslLip lrv rloirrc sorui.'thirLg rlLat
;titothc'r 1)o1'son coul<l cio fot vtiu." \Iolt: loosr'1r.-. Rieckcn [10] r'efels to "intr.gratr:cl rcasorLins
P1'o(css('s as agcuts. OtlLt'r's avoicl thc issuc tontplctr,h'. urLtl 1<.ar-c the irrtr.r'lrlctittiorL ol thcir.
agellts to ther lt'itt1cL. It is t't'coglisctl. hon'evt'r'. that tlLr,'r'r'is llo uglcelrr('1rt ()1r n-iur r it i-. rhlrt
.
ruukcs sornethirLg an ag('1rt.
1.3 Agency, Autonomy and For.malitv
Il rvt'alc to corLfi'ont tlie lrlobletrts
tlLat arisr'h'orn this lac1i ol aslt'crnent ancl rlcfilitiorL" tlLcrL
tlLt' trsc of folrrralisrtts is alllllopriatc -since. it a11ori,s urL;rnrlriguorrs ricsr:r'iptioris o1 r'olrliL'-l sr-.
tt'rus. Folmal specificatiorL larLguages llot onlr-plovirle ir lrlealrs lbl urLarnbigllorls spccilir:atiorL
lnrt also prot-ide prclof svstertrs ancl sets of plool obligations rvhich cra,lile thc crrrr:tnrt tiorr
of rcliable ancl robust rnorlels. Tvpica,11v. such langri;rges are basccl on set thcoly an<1 filst
olclc'r logic. Itt thc ctrtLerLt rvoLk. tc have acloptocl thc specifi<:atiorL language Z 119) {irr trvo
1])ajtl1 l'casol]s. Filst, it plovi<1es motlulalitv arLrl aJrstra< tion ancl is sufficienth' txplcssilr.' trr
a11olv a consistent. unifiecl ar<1 stmcturerl a,ccount of a <:ornputcl system ancl its assot.iate<l
opelatirtrLs. Srtch stntctnrerl specifications enal)lo the clcs<:ripti<trr ol svstems at cliff'elcrrt lr'v
cls of abstlaction, rvith systern coruplexitv being added at succcssivelv lorvel le'vels. Sccorr<I.
rvc vicrv oul t:rttelprise as that of brrildirLg pl'oglirlrrs. Z sr:hcruas ale palticrrlarlv srritable
irL squaring the derna,rrtls of forrnal modellirrg with thc neecl for irripiernerLtation bv allorving
tlansition betr.vccn specification arrd progralrr. Thus our allllroaclL to forrnal specification is
pragmatic rvc need tcl be formal to be prccise about the concepts we discrrss, yet wc w?int
to rcrnain dire<:tly connet:ted to issues of implcrnenta,tion. Z provirlcs just those qullitics that
ale neeclcd, and is incrcasingly being used for specii'ying frameworks and systetris in AI (e.g.
Figure 1: The Entitr- Hic'r'archr
[7. 5, 3])
2 Initial
Concepts
2.1 Introduction
It
rvas staterl car'licr
tliat thclc is a la<:li of conscusrls o\-c1 thc rncitrting of tlLc tcnti itgt'rlt.
arrrl that thet'e are rrral]y <liverse notions of agencr-. hL this section. lrtc irttlotllrt t' tt'ttLls ;tttrl
colr.epts that rvill be nserl to exlilicate oul nnrk'Lstancling of o.rten,ts al.<I o'gle:rtc1y. an<1 |r'or-itlt'
lorrrral clcfinitiols that ar.e usccl stiitsc.c|reltlr'itr <k'r'cl-ilrirLg thc colI(('pt of rt'tr,tttrt'rttrtt1.
6f agclcv liest r.clatcs to that o1 Shohant [13 ri,ho talies art tt,gr:rr't, Itt llt' tttLr- t'rLtitr'
Orrr
'ieri' rncrLtal statc calr lte asclilrecl. -{c<'or'<lirLo t. Shtlharu. sur:h mcrLtal st;ttt'tri1L:isls
to *,hir:h
f
of lorup6letrts srrr.h as lrelicls. r'apaltilitits attrl t'otttrttirtrLents. llut thct<'is rLo trrLi'1rt{' { {)l 1i'(
selet.tion of thenr. This is sensiblc. attl rve too rLr uot clenrtrrrrl tlLat alL agctLts rLcct'ssirlilr- ILitVi'
tlLe sa'r. set 6t lrcrLtal <:olrponents. hLtlec11. n'r' Lc< o.qnise thc liruitatiotLs assrlciilt,'tl $-itlL
ass.'rirrg arr e1r-ir.onrrr.lt <'onrplisirrg hour<lg(.1r('or1s ag('1rts. ancl tonsc<FrcrLtlr' iilthrrlt'irr this
is
rlisr.r.rssi.,l lLcter'6ge1r:ous agcnts l'it1L valr-ing capabilirics. \\-e r1o. lLtx\.evt't'. sllt'<i1r'$'1Lat
rrrinirna,lly rerlttiTed of arL entitv fol it to bc consiclelt'cl arL agcrlt.
The clefilitiol of agetlcy tliat follorvs is intended to strltsurtte existing collcopts i'r" fl'l :tr
possible. It r,vill be iruilt up a,nr1 exterLderl ovel the colrlse of the pa,pel, ancl rvill itru'ol-''e sc'vcral
i'tc'.rccliat. concepts. hr shor.t, we pl'opose a thlce.-ticl hicralt'lLv of entitics tontPrisilrg
that a1l
c.t6jr:cts, oqerrt,s al.d autc.tno?nous agerlf.s. Thc basic icleii urLderlving this hierillchv is
li'orv' e'titics ale o5j1.cts. Of this sct of obiects, sonr(' a1'c agerLts. iirLd of thtrse agerlts solllo
sr'r'tiotLr
aLe arlronol1o1s agelts. This is slLol,n as a \Icrrn <liaglanr in Figu.r'e 1. The follorvirLg
clefine rvhat is rccyritecl lbr erach of thc entities iu tlLe irieralr:hv'
Beib'e we call ruove to a, clefirritiorr of any of therse eutitit's. wo nlrlst first cle{irre sorrc Plimitives.
Tlrc first of thesc ts zt.n ol:tion rvhicli is strorglv lel:itecl to the rtutiort of rt"tlen',:y.
Definition: At acti,nrt is il cliscretc evcnt rvhich changes the state of the environmcnt'
It is cc1tai1ly ltossilile tlLat a,ctiorLs trray rrot bc atouric. but for the' pur'poses of orrl trrocltrf it
is asslmecl that tire property of atouricitv holds for actions rvithorrt any loss of gelera'lity'
Tltc st't'orrrl lrriuritive that
uee<ls cleiining is trrL attribu,te. Attliltutes ale sirnplr. featurcs 61
tlLt'ri'or'l<I. ancl;tt't't1Lc only clLalactcristics rvhich are manifest. Tlit:v nceil not Ic pclccivt,tl
bv itrtv pitt'tir:ulal tlrtitr'. ltut lnrst bc potentiallv perceivabie i1 arL otlliscignt strLsc. (Tp,
ruotiorL ol a ir.atrrlr'1Lclc allorvs anvthing to bc includerl.)
Defirrition -\r
is a pcrceil-ab1e feature.
Lsirrg tlLt'rLotiorLs of actiorLs and ilttribrttcs. rve proviclc. <lefinitions of agcrrcr.' arLcl autolriiur'.
Irt ortlc'r'ttt r1o scl. rvc nttrst clistinguish a,gents and autonclurous agents froru otlLcr c.rrtitic's. \\i,
call tht'st' other crLtitic.s ol.,7cr:/.s. a,n(l (liscuss them lielori.
a,t,tr"ihrir:
2.2 Object Specification
At ti basit le'vel. al object ciirt ire dcfirLc.d in tr:r'rns of its abilitic.s :rrLrl its a,ttr.illrtes. A1 olr jc.<t.
in tlLis sctlse. is.just a'thirLg'ol entin'u'ith no fulther defining r:hala<rtelistics. This proviclcs
us rvith thc ltasic builclirLg blocli to ilevclop oul rLotion of agerr<'v.
Definitiorr: At ob.'jr:r:t. compfiscs a set of actiorrs ancl a set of attlibltes.
In Z. lrt'lolc'coustltrctiuc:t spccilicatiorr. u:e ruust filsr rlcfirLt'tvl)es. Hcr.t vn'r'rlefirLc tlLl spt 6i'
rull lr< tioris arLrl tlLc set o1 a11 attliltutcs:
|Ar:t'il tr t. At.t ribu"t
r
:)
Nttu,itstateschelnacalllic<'ottstr.rctc<1 tlLat<lcfinesarLoltjc.r't. ZsclLcrrraslLavetrl,opar.ts: tlLr.
i declarative. palt rvhi<:h tlctlales r.trliabies ancl theil t\-pes. an<1 thc lt.,n,cr. predicate.
pirlt s,ltich t't'latcs ancl torLstlaius titosc valiablcs. Thc tvpe tif an.v schenra r:an bc colsi<lc,r.r,tl
its tlLr'<'altt'sian proclrtct of the tr'pes of eaclt of its valiables" riithout anl-rrotior ol orclcr.. 1r1t
( ()lril Iiiitr,',i l,r
1lI,'rlir';rr,'..
st'lLcrtta
ltt'1txv
TlLc
has otLlv a declalativc pa1't contairLirLg tu'o varialtlcs. Eit'sl . r:rryto,lileof is
tlLc sct rrl actiorLs ttl tlrc oiric<'t. al<1 is sonrt tirtrt's rcfr.r'r'r'11 to as tlLt' rttrrt,ltr:tt:rtr:r: t.,1 tlLc olr.jcct.
111)1)cf
Sr'<.tlttt1.rt't.tr',i,lltt'te:,cist1Lr'sr'to1,1i'ittttt'r.so1.tlrco1l.je<.t.()1l.jertsal'c.t1Lcl'r'tbr.t.t1r'frrr.c1llr.t1Lil
alrilitv ill tcr'1IIs of theil itt'tions. arLtl tlieil corLfigulatiorL (in a bloarl scrLsc.) irL tclurs o1 thi'ir
irttliltrrtt's. Tlit'<onfigutittiorL ol arL olr.jcct irLr'lutlcs lefi'r'cnces to tire borlr'of tht,rilr.jcct arrrl
its positiori. irrrrl is sirnilal to tlic uotiorL usecl liv Gootlu-irL [5]
.
Ob.jt t:t.
capo"ltlt:of
F Ar:tirtrt
o"ttribut.e:s
F Att.ribu,te
Atttilnrtt's ale rnauilcst aud arc poteutiallv ar:cessilik' by arL obseLvur'. The capal-rilitics ol arr
objc<:t in lernrs ol a<:tions. lty corrtrast, zrLc Dot neccssarilv oltservablc.
Fot cx;ttttplr:. corLsitlcl a I'obot rvitirout a porvel' supplv. Sinct: thc lobot iLas rLo lrorvcr. its
<'altabilitics alc se'vc'r't:1',-lirnited arLcl incluric jrrst those u'hich lely orL its plLr.sical 1)r'('scrr(('.
str<th as supporting things, weighing things dorvn, and so on. The attributes of thr: robot
sptrcilv that it is 1tlue, that it is rrpriglLt, that it is large, and cithcl such fcatrrles. As a
second cxiirnplc, cotlsidcr a coffec cup. Its capa.bilities state that it can support things and
tlLat it clrt corttain licpid, for exarrrplc, rvhile its a.ttributcs state that it is stable. rvhit,: and
nr.a,de o1 china,. (These exarnplcs will bc developed further to distinguish bcrtween agcnts ancl
arrtorrornons agcnts.
)
A1 o|.it:ct rnust bc situaterl in a,n environmcnt. Wc take an euvilortrnt:nt sirnpiv to lle a sct <tf
attr.ibutcs that clesr:ribes a,ll of the featules of the wor'1c1 and ali of the cntitics (objeqt'. :rll('nts
or ?lllronolnous agunts) in the rvorld. (Thereis a cilctrlarity hert'rvhich rvill bc discussed 1atcr.)
ErtuirctrL,rrt
ent
P
Attribute,
\\ie rrrust a,],so spt:cifv al action selection fir.uction. rviriclL deterrrrines the next a,ctions of an
olric<'t i1 an crrvilorrrnent. For exarnlllc. if a piece of pal)er is placecl on top of otrr rtlllttt, tlLert
\\'(. (':ur strv th:r.t tlLe lobot wiII .ru.pltorl tht: pa.pct'. Or', if tea is potrred iuto the coffee cup. tlictL
tlrc r:rr1r wtll r:orttain the t<:a. In ltcith of these cases) it is the ttl','iLounrt:ttt that cletelnlirLcs
tlLc, lext action of the objc<tt througlL thc lilacemclt of the papel artcl the pttuliug of tire tca.
TlLc actiorrs are thus Ttassirte actions.
In tlrc Ob,iectAct schema below, the cleiinitions from thc Ob.ie,ct scherua ale incltr.<1ct1. arLtl thcrL
tlLe actirrrL-selection function, ob,ju:tactic.tns, is defined as a totalfunction frorrt Erutirottrn't:rt't t<t
P Act,iorr,. That is, given any elviroument it rr'ill tetuttt a (possiblr-emptr')sct of actions. TIlt'
asscltiol in tlLe prcdicate part of thc schernii constrains the'next :rctions ttl be taiien (givt'rr
lrv alrlrlfirrg objectar:t.fons) to be rvithin the oltject's colnpetclrce. It catt lic lead pt'ct'ist'1r'
as: giv(,lr anv t:rLviLonntelt. applving ob.jer:tact.ir.tn.s to that t'ttvilotLtttt'trt ritill L('t11lli a s('t
a< tions ri ltich is a subsct of thc a,gents calta.bilitics.
()1
Ob;ie:r:tAct
Ob'ierl.
rtltject,o,r:tiorts
'.
Ert,pirot-ntx:rtt,
-
P Acti'oIL
V e:rnt '. Enuirontnertt o (ritiect.o'r:ti,orr"s e,rt'u)
\\i'
cern also rlcc:lale art irlstancc
C crqxt'bleoJ
of art t'nvilotLrrtettt:
Ett,rr
rt t,ui,r'ot
rrt x:r t,t.
r'.rt,ui,rvnunnrrt
: Et r,ui,r'or r,rn,e:t
+I
t,t
I
Norv. rvc ca1 clefile the sta,te of an ob.jcct in its ettvilorttnent. hL tho Ob;iectStutt: scltentit.
rhc. infrrr.rrratiorL from tbe Enu alx| ObjectAct schemas is iucludecl. a,1ong rvith /ristorrT rvlLiclt
re.prescnts the sccluence of (sets of ) actions rvhich tire object has perforrrreci. Each of thcse scts
of actirins must comprise only those actions of rvhich the ob.jcr:t is ca,pable. rvhich is statetl irL
tlLe sr:lLcrrra. plcclicate as: any sct in thc lallge of tiris scquence rttust ltc a strbsct oI cupableof
Tlre prcrlicate is meaningful because sequences are clcfiuecl it Z to bc fiurctious froru thc sc't
of rLatrrliil rprmbers to the r:ornponcrrts of the seqllcltce. zittcl so thc langc of a sccprencc is.just
tlL<' sct corrtaininq the elemcnts of the seql1elc.e.
Thc attliliutes of the object are a,lso coustrainccl to bc a suirset of tlLose attlilrrrtes irL tht'
slvirorrntent. This is because the ob.jcct is part of the ettvilottttrt'rtt ancl its a,ttlil-rutes urust
tirerefore also be attributes of the environlnent.
To ai<l sclrenra. reaclability, we calr also a,tlcl r'etlundant or reco'uerable inforrnation to the sclLc'rua.
For exarrrple, tire variable, willdo, specifics the next actions that the agent will do. wiric.h is
r.e{lrrclant silce it is recoverable in exactly the way it is spccified. It is detcrnrined l-iy applvirLg
-
t
lr.:
ct b.j
ect
ur:tiotts lirlr: tiorr to the r;rruiron ntrnt.. This rccovelaJrle itLforrna tion is sepalatc'cl
tlLc rcst of thc s<:hcur:r bv use of
a,
1l'orrr
small space. hL rvhat folloq,s. we uso this corr..-cntiorL to
a<lcl
such aclclitional infolnration to a schuma.
Ob.je:c:tStu"tt
Ertu
Obier:tAr:t
history : seq (F Ar:tiorr,)
'u'illtlr,, : F Actiort
V a.s : ran ltzstltry
tnilkl,,
=
r
rzs
C capabler,,f
olt.l, r'ltu:l iotr.< t:n tti t'()?L'tuc?tt
Thesc clr:firLitiotts lLale an inlLclclnt cit'culalitr'. horvevcr'. Objccts ale situa,terl iu errr-ilr.,rLurtlrts.
btrt cnvilonmettts are.just sets of attributes dclivcrl fronr the entities (ol objccts) irr tlLc
crtvilorttnent. Thc attt'ibutes of thc crLr.'iroumcrrt rnust thclcfore iirclurle thosc ol tht'o1r jt'r.t
itscif. This is a trst'ful abstla.ction rncr:hanisnr that sc.r'r.'cs to reclucc thc <'oruplc-titv ol thc
u,orlri until w(' rrcc.cl richel illblntation.
E"'clvtitittg in the c'rtr-ilorLrtrt'nt is leplescrrrtt'11 sirnplr.ilr tcr'lns ol attliltutcs. Ii tlLc cur-ilorLlrcrrt
is itlg'trvs acccssiltlr'. therr u,c rLt'ctl ortl-u'note tltosc attliltutcs that ulc rr.lc"r-arrt to tlLc tlrsk at
itarrti. arld ( a1I liurit tht' infolmation florv. \\'it1L lcsouli c' bourrrls. sur'11 lcsirictiorLs alc critir ir1.
it is rtct'cs.it1'\'to ilccL'ss irLlirlrnatioti aborit thc. enlilonrrrerLt. rr't'irrstirrLtiatc olt.ioct
rttotlt'ls (rtl s<iterttas) u'ith l'eievalit itttt'ibutes. art<l ignole thc lcrnainrler'. TlLus u'r'rlistiugrrish
olr.jccts fit-rur thc ctLvilourLt'rLt (br.'t'lustcling attlil-rutcs. for crarrrplt..) clrLlr-n'1Lt'rL it i:1ls('1111.
\\'hetter.-c't
TlLis rtotittrL ol irLstarrf iatiort is tlLt: lrasis of this flarncg,r,r'li" 1i-rl tlLlorrglL srtct cssivc irLsr;rrLfi.rf iorL
s't'irL<r't'itst'tltc courirlc'xitl ol r'rLtitics tr-r introrlur'1, 11{'\\'(o1r(('1)ts. \Iotcolcr'. it i: ir rrofiorr
tlLat is cflirt tir-c irL fr.it rrsirrg attetttiorL orL lr'lc-u'arrt asirr'< ts. arLrl lirltitirLg f hc urrtritrrLl iil r'ftirlt
nt'ct1cd to lirrLctiorL ( irt)al)1\- irL lcal-u'cir'lc1 -if nations.
2.3 Object Operations
thc rvav in rvlLir'h its next a<'tiorLs aLc. sr'lc< tccl. \r.xt
rve'tlesclibc horv tlLr'pclfolmance of tlLcsc actions affects thc enr..ilorLtncut irr x'hiclL tlLc o1r.jr-ct
is sitttaterl. To <1o tltis. rve need to irLtrorluce operation schemas. Opclation schernas irL
Z clesclibc tlLc rclationshiir betwec.rL trvo statesl the stater bclole the opr:ration. ald the stirtc
aftcr thc opt'r'a,tiort. -\fter-statr: valia,blcs are clistilguislLt'11 ri'ith daslLcs.
Filst. rve clcf.nc'rvhich valiablcs of a state renr?ri1r rurr:hanged altcr a set of actions. TlLc
LOb;jr:r:tStale schema statcs tlLa,t rvhen att Objer:tSlolr: r:hanges (throrrgh pcr'lblrnirLg actiurrs).
its <'orupctcrrr:c cloes rLot <:1Langc. an<1 its action selection fiurctiorr rlor.s not clLarLge. (T1Lc -\ is
tlLc narning r:onventi<trL tcl dcscribc il chzrnge of state. )
So {ar. w(r hav()
<1cs<
r'ibccl au object
arL<1
6
LObiectSt.ate
Olljr:ctStat,e
ObjectSto"te'
':
ctrp1bleof
objec.tu.r:tion,st - objecto,ctiorts
capnbleof
htterv"ctirtn,ts sintplr'rvhat happens rvhcn a,ctions are pelforrned in att environtllcrrt. Tht'
effccts of arL interaction on the environrnent aLe cictc'rmineci bv applving tlte e.ffe:ct.irttr:rrtr:tirtrt'
fu.nctiou in the axionr clefinitiorL ltelorv to thc cuLLent ettvironnteut a,nc1 thtr a'ctions talicn. TlLis
tr,xion rlefinitioiL is a gkrltal r'at'iable anrl is conseqttontlr.' alrvays itt scope. \\ie rcclttil't' onlv
ole lulction to clesclibe al1 irrteractious, sincc att actiol ri'ill result iu thc s:rtne t'lLattge to illI
envircinmettt rvhethcl talieu liv au object. agent ol autollolrrous agent.
At
e.ffectirr.tetv"ctir,tn : Enui,tvnnr'ent '--- F Action'
-+- Ert'tti'ron,nt'r:rtt
\Alhen an otrit'ct intelacts iu its envirorlncllt a,n<l perfolrus an actiou. l;oth thc statc of tlLc
olr.ject ancl tlLc c'nvironment clLange.. replescrrted h Objer:t.EnuItt,te:ro.ct..ltv -\Olr.ir:r;fStalr:. (Rt'
rlc.nrlreL t,bat Obier:tSt,o,t.r: ilclrrrlcs Emt.) The histolr- r'at'iallle is rtll<1atec1 llv cutlr';rf ,'trrrtirLq
t[c c1r'r11t sct of ar:tions to tlLe entl of thc seclrcrtce. arL<l thc ttcu'enviloltttrerLt is givcrt 1lrapplving r:.f;t'r:ctirft,etn"r:t,iortI,o thc olcl euvirontttertt an<1 tlLc'ctrtlettt a<'tious. TlLc Iast lint'statt's
tlrat tlre actiolts l,r'1Lich follos' tlLc crrllerLt actiotls at'c lbutt<1 1tr.'apph.'ilg ob.ir:r:trtt:ti,rtri.s to tltl
rrt rv crLviLonnr<:rtt.
O
b.i e ct.
E
I
r r,u
rt,tr : r' r t, r:t.
\Ob.je:r:t.St.at,c:
Itist.ot'r1'
- ltist,onl' \'utill'rl'o)
- t:.f;fer:t.i,rL,tt:rrt,r:t'irtrr,
entti,r'olrtn,r:rtt.t
u,i,l,l,rl,r
/ :
r
tb.'j r;c:t.o,i:t,ir.tr
rs
r:r r,uirct|Lt
t
ert'uilvrt'rnert,t. tt'il.l,rl'o
rc: r
tt.'
Thc t.lLat.actclizilg Ii'atrrlcs alr. tlLc set of attiorLs u'hitlL tratL lr<'pc'r'Iitltur,'t1 irY t1L,' ,,1 ,.1", f ;rlLr1
the iittlillrtes of tlLe olr jcct. TlLis is not sufficicnt for agcrLcr.-. arL<1 rr'itltout lultlLcr'<lt'tail or'
specialization. is iriatiecpate fol a <lefinititlrr of agelrc\-.
3 Agency
3.1 Introduction
Thcre' arc lrla11\' clictiorLarv cicfinitions for :rrL a,gellt. A leccrtt paper llr' \\tloldritlge iirrtl
ol
Jeuriilgs [20] quotes thc defirLition of an agcnt a,s "olle who, or that lvhich' t:xtrLts l)o\vel'
u'otrc
given
as
r,vhich
is
of
a,gent
seusc
sec.oncl
thc
omitted
thcy
Horvcver'.
proclrrccs a1 r:ffec.t."l
who acts for a1other..." This is inportant, for it is uot the acting alone tltat clcfiues agell(Y,
brrt the acting for sonrer.tn(: oT' sonlething that is clef.ning. Intleecl, \\boldridge arLcl 'ItrrLrLirrgs
a,clinowiedge the difficulties ir a purely a,ction-bascd alalysis of agencv.
r'lhe Concise OrJord Dictionnry of Current English (7th edttion), Oxford University I)ress
Ttl trllcic'lstarlcl ltcttcl rvltitt actr.ut11r.'colstitrrtes trn agetrt, r:onsiclel th<: exarllrle of a coffc.c cu'.
A t'u1i is arL oltjt'<:t. \Vc carr regar<l it as an agr:nt anrl asclibe to it rucntal statc. b1t it selr.<,s
no trscfttl 1)l1lposc ttt r1o so rvithout corrsirleling thc r:ilcutnstalrccs. A cup is an agent z/it is
contairlirrg a liquitl iinrl it is cloing so to sornc enrl. Lr othcl rvo1cls. if I fili a c1p *'ith cofft,r,.
thcrL tlLe cttlt is nlv ag('nt it sc'r'r't's 1lr\-1)111'l)os(.. -\lterrLativelv. thc <:1p s-o*1<i alsr 5<: a'
agt'ttt if it rvas itla,cetl upsicle <kxlrr on a, stach of piipels anri usecl as a papel'\\.eight. It rvorrll
nrttlta art agctLt if it rvas jrrst sitting on a tablc. $:ithorlt scrr\'l1rg ally pllr'l)ose to a1]\. agent. I1r
this casc it rvorrltl lle arL cilt.ject. \ote tlt:rt rver <io rot recprilc arL cltitv to lte i1tqllige't fo. it
to lrc au agcnt.
TlLus agents a,re jttst ob.jects rvitlt ct:rtain <lispositious. Thev rnav alrvar-s be agents,11r'tlrlr1tltlv l'ct'cLt to llcing objc<'ts in ccltain cir'<:utttstances. This rvill bc exltlorecl fitlthcr 1atsr. Fo1
thc rttorttent rittt rvill corLceutlatc on the rratule of the disposition tha,t charactcrizes au aeelLr.
An olt.ject is an agcrtt if it scrves a rrsefirl pl11'poscr cithel to a <lifferr:nt agent. or. to itsclf. irr
rvlLi<h < irse. the agr:nt is o.tft,orlc.ntxttt,s. This lattcl r:ase is discussecl ftrrthcr' 1ater.. Specificalh..
art agtrnt is sornt:thiug that'a,dopts'ot'satisfics a goal or sct of goais (often of ancither.). Tllrs
i1 I rvartt to store coffcc in a c111). then tlLe cup is rnl agent fol storing cof[t.e. It ]r1s lrcqrr
o.st r"ibr:rl or has o,doptetl rrrr-goa1 to have tlLc coff'cc storr:11. An aecnt is thus clefinocl irr r.t,littiorL
to its goa1s. \\ie talic a tlatlitiou:r1 r'icrv ol goals as rl,:scrilraltle r:rrvircirrnrcntal states.
Definition:- -\ goo.l is a statc of aflails to bt'achic.vcrl in tlLt'crLvilorLrut,rLt.
Definition: -\t rtqr:rtt. is art instnrLtiatiorr ol arL objc.< t togethcr u,ith arL associatc'tl go:r1 r.,r'sor
o1 goa.ls.
3.2 Agent Specification
Br'1olr'\1'e call t1cfine lt sr'hcma
lirr
a,qcncv. rrc
tlLat rlcsclilic a state of affairs irr tiLc
Grrt,l,
-
goals to 1tc jrrst a sct ol attlilrrrtt,s
F Attt'ilnr,tr:
Tltc stlLcutit fol
At1,
nlrst cl,'fine
grot'1r1:
ztrt agcrLt
is sirnplr- that of an olt.jct't but u'it1L tlLc adriitiori o{ gclals.
tLt.
Ob;jet:t.
goo"ls : P Gctal
ooals
I \\
Tlrrrs arr irgt:rLt has ot ts ascribr:r/ a set ol goals rvhich it retairLs o\:eL ir,ny irLsta,rLtia,tion (or lifc
tirno). Orrc objcct ura,r'give rise to clifferertt irLsta,ntiations o{'agcnts. An agc.rLt is instantiatc<1
Ir'crrrr arr object irr lesporLsc to a,nother a,gcnt. Thus agerrr'.v ts tt'urtsienl, ancl arr ob.jc<'t rvhich
ltecorncs iln a,gerLt a.t sotttc tiruc rnav subscqriently rcvelt to being tin objcr:t.
Rt'turuiug tcl thc ctlp cxalnple, rve ltar.e an a,gcnt rvith the sarne attributes and acticlrrs as
tlre cnp ob.ject, but now it cnn be ascribed the goal my goal of storinq m,y coffee. Not,
everyolle will kuorv that it is a,rt tt,gent il this rvay, hos-er.el. If, for cxarnplc. I am il ii cafe alcl
tlLcre is a hal{:fuil cup of lemon-tea on r}ry t:r.ble, there are sevcral views tlLat can be tzrlicn.
It carL bc rcgarclecl by the rvaitcr as a,n a,gcrLt for me, storing rny tea, or it can be rcgzrrrierl as
an ol)jec.t selvilrg iro pl1t'pose if the rvaiter thinks it is not urittt:. The view of tht: <:up as art
olt.iect ol agent is relevant tcl rvhctther thc staitcr rvill reurot'e the cup or leave it at fire talllc.
Ngtc t[at we al('not sliggeiting that the cup actrtalir-possesscs a goal,.just that thcre is a
goal tlriit il i: sirl irfr irLg.
CotLsiclcr. also tlLe 1'ol)ot exaluple. arrrl supl)ose non, that the lollot has a, porvel suppil'. If tlLt'
lobcit has rLo gon,1. then it cantrot use its actua,tols irt attv seusible lvav llut orrlr'. per'haps. iu a
1arLc1o1r rvay, 11d must lte ccxrsiclcrccl an ob.ject. AltetrrLa,tir-eh'. if the roliot has sclruc goitl or
set 9f gcllls. rv[i<:h a]lol'it to eruploy its a,ctu.ators iu sorne dilectetl waY, sucl] as picking trlr
1ctlpl or calrving a table, ol liveting a pancl onto a hull, then it is trrt agent. The goai nctlrl
rLot |t: explicitly leplesented. but can irrstearl be implicit in the harcl'"vale 01' software clcsigrr
of the roltot. It is mclelv nccessarv for thele to be a goal of somi'kinc1. (\\ie also a11orv goals
i1 iigents to bt: r'eplacccl bv higher'1cvel ruotivations. trr.rt iliscuss tlLirt lattll iu thc contoxt clf
autonorrrv.
)
Thcse exarlplcs highlight thc lange of ltehaviorrr that is availaltle frortt agt-'rLts. Thc t'offec culr
is pirssive arrrl hils goals in4roscdupon a.nd o.scribe:rlto it. rvhilc the lobot is t:apa1llc <lf activclr'
lralilnrla.ting the cnvironnrent bv perfonning a,cticirts clcsiguecl to satisfv its goa1s.
\\i: 16rv i1t1oci1<:r' ltelccption. -{rL agcut irt itrt envilollltt('nt nrav havc a set tlf llelccllts ar-ai1altl<,'. Thesg are tlic possilile atl,rilrutcs that arL agerLt corrlcl pclt'eivc sub.ject tti its cairalriliti<'s
atr<} cnrl:nt state. Hou'e'u'et'. due to iinritt:d 1'esol1rces. a1l agent rvill uot nolntallr'bc illrlc to
litlccive all thosc tittlibutes possible. arLd bases a<tion ol n subset. u.lLich s't'call t\a rr,r:trLtt,l,
at all. Iu tlLt' ( its{' {rl ;r { r11).
1)qt.ce1)ts of atL agerrt. Sorrrc agclrts rvi11 uot ltc iiblc to 1)(11'ccivc
1br cxanirlt:. thc set of possiblc pct'<:e1tts rvi1l lrc c'1r]1)t\'. artcl const:clrtcrrtlt' tlLc st't of actttitl
pclcepts riill also 1tc cm1it,v. Thc loltot. horvt'r,et'. rtral har-e scr.-elal sollsoLs uthi<'lr alltls'it trl
pelr'r.ive. Tlms it i< 11,t ;r lo,lr1i1nlrr,'rLt of arL agcrLt tliar it is alllc ttl per<cive.
For.clirlitr.ol expositic,rl. s'e. rlcfirLe a V'ieut to bc tlLe pelcc'ptiort rtf att Ertrti,rvrnn'r:tt't. ltY arL
agcrLt. ;rrLrl n'lLit'h is just a sct of attlilltrtt's.
Vi,r:u
-:
P At.t.r'rlttft.r:
It is also ilrpr-it't1rLt t() lrotq tlLat it is orLlr, nrt'urLingful irL otu rrroclcl to t'onsitlc'r'1rt'r'tr'Itttal
llrilitils irL tlrr'('()ut('xt 9f g<ia1s (ol rriotivations u'hii'h gir-t' r'ist'to goals). T1Lus. $'}tt'tt t'tltt
sirlt'r'irLg o|.jccts u,lLirh lLitvr. tLo golls. per'<t'ptttal alrilities iilt'ttot lclcr-itttt. O1r.j''' tt 1":lr,1Lrl
clile.ctlv to theil er5..ir.o1rrre1ts trrLtl nrrilie no use ol pelcepts e'r'en if tILer-arlc availallle'. \\i'sa!
tlrat percclltual <:apaltilities ale irt,eTt. ttt the corLtext of olljec.ts.
Irr thc. sclrerna for a,gcnt pcrception. Agr:rttPerr:ejtts. \\'e acicl fitrther detail to tlLe tle{initi.n of
agellcy. a1cl so i1cluc1e the schcna Agent. An ageut lLas a set of percciviug actiorrs s'hi<h ale
a srrlrsct of t1e capabilitit:s of :irr agent. The firnt'trotr- c(lrLperceitrc, clcterrnirLt:s tlre attlillrtcs
that ar.e pote1tia.llv avnila,ble to an agcrrt through its pelceptiou caira,bilities. \\ihtlr aPPlit'tl.
its algrrnt:nts a1e th(,(ul'rotrt envilottttrcttt arLcl tlttt agerLt's t:apabilities. The secort<1 pt'ctf i<'atc
lirre st:ites that those <'apa.bilities rvill bc plet:ise1v the sct of pelceptua,l capabilities. FirLallr'.
tlrt: furL<'tio 1.^ urill7.,r:r.cr;ioc. clesr:r'iltes thosc attliliutes lr'hich are actuallv pt:rceivctl bv an agcrLt
and rvill always be a,pplic<l to its goiils.
9
Aqr:ntPr:rcept.s
Agerft
Tterr:r:i,uirr.q
o,ct.iorts : P Ar:tior
t
rttrtpe,rrr:iue '. Ertuirortrn,erlt,
P Action
ut'illltr:r'c:eiue : P Goa,L
Ermirctrrnterft
-
p
e,r r:
e:iu'ir ry o, ct,i rtr
rc C
cup ab
-
I
r
t-
Erutirrtrnn,errl
Vir:tn
nf
Y r:nnr : Enrtironnt,etft; o.s : P
Actirn
o
os € dom lut"rryterr:eute errLl)
dom utill'perr:r:iue : {rloo,ls}
*
as
= 1tr:r.ceiui,rtga,r:tiorts
Dilct:tlr" corlesPonclirLg to thc goal or goals ol an agr:ut. is arL acti61-sgler:tio' llurr.ti.rL. 11,
1it'rlrlerLt ort tlLtl goals. cttLlertt envirotttncnt arL<1 tht: actual irclr:eptio1s. This is s'r,cifit,rl i'
Aqett't.Act' belorv, in tlLc sallIC wav as ObiectAcl pleviciuslv. the lclatccl preriicatc c'*srrri',f tlirt
tiic fitl1t:tio1] L(ltur1ls a set of actiorLs tvitlLin thc agcrrt's conrpctence. Nott: also tlat ii tlLt,r.t,
a1(r llo Pcl'ceptions, then tlLc action se'lection function is tlcperLclelt orrlv ri1 tlLc otryit,rrrrrr.,rrt.
as it is lr'itb ob.ier:trt,r:t,iorts in Objer:tAr:t.
AgerLtAct.
Aqr:rr,t
rt.qerft,o,r:t,i,orts : F Gc,al
-
V'ieu
-
En,u,itttntlr:tlt
-
F Ar:t,,irnL
VrTs:FGorLl:u'. l'ieut:r:rLt,:Ernti,r'rrt'rrtr:tttci'rtrJr:rrtul:tirtrugsuttnt)Cr:o4ttLbLeol
dom
\\i'a1srr
o.r1
erfio"r:tiort.q
clefirLc
-
{goa,ls)1
tlit'statc itf an aeerLt. This inclrrdcs
tu,r.r r.'aliables. I)()ssI)et,,r:r:pl,<. tlcsr.rilrirLg
t1tr,rsr'1li'rr:c-pts1lclssi1l1t'irrt]te'<.tll'r'ettttlrL'u.iLclrtrrr<lt1t.it1|(1rl"r:tlt,rl"I7lrllr:
art' tltt'
('1r1'1('1It (at'trral) p('r('('1)ts o1 t1Lc agcrLt irL tlLr' < ullcrLt cnvilorLrucrLt. TlLcsc r-it1illrl1s
ltt.r't'il1t.lt1atr'rlrlsirig1|1t.'t:tltt.1.lr:rllr:tttr:tllLt1
tl|l.'jt:t:t,tl,r:t,,i.tlrisr.ar.iallicfi'tltrLthc
tht' Aqt:rr'tAr-'l sr'hetnit. Since goals alr'1ixc.c1. r'hanqt's to tlLc o.r:t.tt,rLlpr:r'r,e:7tts <'f tlLc aqclt afli'r.t
rltr' ltrrtt tittrLalitv of thc agi-nt u'ltcrt ccnrrlrared to thc lrase olr jc< t fi'orrL rvhich it is crlati'r1.
Aqr:r'r,tStute:
AgerftPercepts
AqerftAct
Ob.jectStote:
pcts.<1terc:epts
:
Ertuirornn,ent
ar:t,rr"o.lpercepts '. Vieut
u.ctrut lperr:e:pts C possqtercr:1tt,s
po-ssperr:e|tts : curLpLrcein,: r',,rtti.r.,,trLrrLt nt. pe:r.c:eiuirtrlrt"ctiorm
o"ctttct"lytercepts : uillpercr:iu e q oals pct s sytercepts
o bj ect.o" r:tior LS - og (r Ltoct,ions g oa,ls actr r"o,lperr:ep t.s
= t )) .+ (posspe,rrx:pts : \ j)
a(JeTltactions goo"ls actu"o"lperce:pts enttirr,tnrne,rtt
(pe.rr:e,iu'irxloction,s
uillrlo :
10
3.3 Agent Operations
As rvith ob.jec.ts, rve clcfine l'hich of ther agelrt state valia.blcs retna.irt rrncltangecl aftel a st:t
of actions has been pt:rforutc<1 bv that agcrlt. If ant' of tltcstr lat'i;rlties el'el <1i11 charLgc. a
diff'clr:nt iigcnt strlterua rvorrlcl hiivc' to llc inst altiatecl.
LAgentState
Agerr.tSto,te
AgentSto,te'
crtpuble,r,,f
qoo"l.s'
-
':
cap1bleof
gr,,als
7terceitting o"ctiort st
r:u,rryterceiry
e'
:
:
pr:r'ceiuirtq o'ctiorts
crlnpe,rr:e:nte
u,illlr,rc,'iue' - wiLLp,
o"g
ert,t.rLct,inrt,,q'
:
t t,rJ
r'ceh,t
ertta,ctioTL-c
rLrxv sllccifr- lLrxv arL agent intcracts u.ith its envir'orrtnt'lt. ,{s a lc'strlt of itlt irrtt'r';tt tiolt.
t1e c1'u-ilolrrrent charLges arrcl agent state chauges s'ith cr:rtain valial,rles trrtaflc<:t't'<l as tlcfirlcrl
n \ArlrtttStrt"te. TlLc histolv arLrl enr-ilonntent ale alfcrecl irL eractlr'thc sarntl \\'tl| ils \\';ls
\\t'
tles<:r.ilrerl i1 the ecSrivalent Object. schenta. ancl the firLal lbur plcclicatcs of Agr:'n,t.Ert.uItftt:t'tt,r:t
1r'e rc<1rr1r1a1t. ilrt shorv e.xltlicith'hou'tlte sr:httma t-alialtlt:s arc upclatecl'
Ag r:n,t.Ert
\
u
In,t,r;ro"ct.
Aqr:rLtSto,t.e:
- lti.st,ctrtl' \wi,lldrt)
wtll,rl,r.'
t.'i o
t,i,r t't r
e r ru i,t r t t n t t' - t:.ff
pr,tsslttrr:t:y.tt.r' - r:(ntpe:'il:ei,ur: c,:rt'uirr-tn'rt*:lLt' pr:'rc:e:iuirtrlrtt:t'irttt'c
rtr:t.rt,u,l,2xtr:epts' - tuilLpr:rrt:'iur: rlrtttl,s 7.,t-,ssytrt'r:epts'
ob.'jrr:t.o,ctiorLSt - (I(l(:tLt,rt,cti,rtrts rltxt'ls rt"t:ttto'lpc:r't:r1tts'
tnill,rl,rt' : rtrle.rr,t,a,r:t,iort.s 11cta,l,s o,ct,u,rtlpr:m:r:ptst r:nuirrtrltnr:rt,t'
/t,i,st.t,,t"y'
r
t
e:
t
4 Autonomy
e c:
r:
o, r :
r
t,
as Motivated AgencY
4.L Introduction
S. far u,e ha.,.e clcvelopccl a cle{inition of agencv. Horvevcr. thc definitiol lelies upon thc
cxistelc:e of other ilgents rvlLich provide goals tha.t ale adopte<i in ol<lel to ilstatttiatc illl
agclrt. I. o1clc1 to grouncl thc chain of goai adoption. tci escapc rvhat could be arL infiilitc
also to ltring ont the rLotiorL of rtrtt,ctrtortr,g. tve irttlo<I:uce ttt'ttti'rtrt'tiort'.
Gloultlilg the hierarchies of goal acloption clcmands that rvc havt: some agcrLts rvhich can
gcrLe'ate their ow1 goals. Tliese agents aye autctnon?o?r-q agellts siucc tlLey ale riot clellcrLdt:ilt
rrL tlLe goa,ls of othcrs. Autorromou.s agents 1)osscss goals whiclr at(' (len,('r(ltetl fro:nt $titlLirt
ratlrer tlta1. s"4optr:d ftom othel agents. TlLese goals arc gelerated front rn'cttittrt"tiorrs, rvhicir
ca1 bc t:o1si{ered to lte higher-level norL-clerivativc goals rvlLich t:harar:terizc tht: lLattrre ot
I'egl.c.ss. ancl
11
tlLt'agcrrt. N{otivations arc. lLolvevcr. qualitati',.clv cliflirlcnt i1l t[2t t|cv at'c not clcsc'ilialt1,
statc's of afla,irs iu the cnvitonrtrcrLt. Fcir'cxarnple. r:onsirlcl tlLc rncltir-atirn, rpr:r:rL. Tlis <l'r,s
rlot sllt'<ifv a statc'ol affairs to bc a,chievtrtl. nol is it clescribablt'in tclnrs of tht'elLvir.rrLur.rrt.
lxlt it
(if oth<'r'rrrotivations pcrrnit)
givc. rise to the gerreratiorL of a goiil to
lrauli.
^
TlLc clistirrr:tiort ltctrvet:rL the rnotivation of greerl arrrl tlLc goal of loltlting a lralli is'.5
t'l.ar.. *,itlL
thc folrucl pl'ovi<lirlg tl I'easoll to c1o tiie la,ttcr. arLcl the la,ttcr sitccifvilg rvirat llust l)o (lou(,.
tuar.'
Definitionl. A
rn,ot,i,uotirnL,
is any clcsirc or'plcfercrrce that
<'an lcacl
to thc
gerLeration
arL<l
a<loPtiolL of goals artcl u'hic1t affer<:ts thc: outcolrc ol the lt:asonirrg o1 |elLaviorrral tash iutt'rrtlr,<l
to sa.tisfi' thosc goals.
(This
rh'arvs orL
4.2
Autonornous Agent Specification
thc <iefiuitiorL usecl lir- Krurrla [6].)
A rn'ot,irtrt"t.c:rl tt'qetfi, is thtts a,l agent tltat prrlsues its ou,rL a,gerLcla fol leasolilg a1t1 lr.lLur.ir'r
in accor'<lance tvith its irLternal motiva,tion. Since rnoti',.ations grouncl the goal scrL.r.atiorr
regl'oss. rve claiul that it is nrotivatiorr tlLat is the clitica,l factol in achiur.ing alrtoltolrrr'. ,\rr
otr,ttrn,ortr,otts o,r1e:'nt. rutrst rLc<'cssarilr. bc a rttotiuatetl agelrt.
Definition:. Att o'rr'tott'oItlo'tls a,gentts an instantiation of irlr agcrrt togctlLcl rvith 1rL ass6r.i1tr'<1
sct clf nrotir..atiols.
\\rc can tlo\\r sPecill- ilrl itlltollorlrous agcut. Filst ute rLcline thc set of all rnotivatiorrs us ir lrlsc
l\-i ) (':
lMotiuatirnt,)
ArL ittttortoll)o11s itg('1lt is <lcfirtccl as,illI agent n'ith urotivatioris arrtl sorrLt'1rott'rLtilrl rrLt'irrrs ol
lrttlLit'u-iottt itL tct'nts of tlLt'crLr..i1'orLurcrLt anrl thesi'ntotivirtious. Itr othcr u.or.r1s. tIi'
bt'lLaviorrl t.'l t1Lc iig-t'rtt is <lctclrnirLctl bv botlL cxtr.r'rL;r1 arrrl irrtt'r'na1 factols. TlLis is rlrrirlit;r
tivt'h.'<lifti'r't'rtt 1t'ottt illt agclIt rvitlL goals lrecausc rnotir-lrtions ir1('nolr t1r'r'ir-atir.-<'arLrl gor.i'rrLcrl
cvllrrating
lrr-itrtt'r'rtal irLattt'ssilrL'rttlt's. rvhilt'goals ale tlr'r'ivativt'arLrl lclatc rlilcctlv to rrrotir';rtiorrs.
A
t
t,t,rtr
r,
o r r t o'r
L,c
A
q e-r t t.
Aqr:rt
r n, r t t,i,t
t r
t.t'h t
r
t.
s : P M o t:i'u r t"t i o rt,
rttot:iltu,t,iltrr,s
f \)
ilhrstlatiorL of tltesc i<1cas. note th:rt the cup ('ilnnot 1ir. corrsi<lererl arrtorLomous bi't'arrs<'it
cartrtot ge11e1'ate its orvn goals. The lobcit. horvcvc.r'. is poterrtiallr' a.utonoutous irL tlLc sr.nst't1Lat
it rna.y ltave a rtrcclLanisrn fol internal gonl generation rleperLcling orL its erLvironrrierrt. Srrpposc
tlte lolt<-rt lt:ts tttntil'a,tions of at:lLicvernent, lnrngel arL<l self,plt.serlvation. ri'lLulc achicr.r:rrrcnt
is <lcfinccl irL tt'lms ol fixing tt'res orLto a ca,L o1r a prorluction 1inc. hu.ngcl is clcfincrl irL tcr.nLs
ol maint:rirLing lrorvcr' levels, arrd self-preserva,tion is cleJinerl in tclms of iivoicling svstenr
ltrtta.lidorvrrs. hL norntal opera,tiorr, thc robot r,vill gcneratc goa,1s to a,ttach tyles to car.s throtrgh
a series o1'subgoals. If its power levcls are low, however. it mav replar:e the goal of attaching
t-vrcs v'ith a uervh'generatccl goal of rccha,rging its battelics. A third possil-rilitr- is tlLat irL
satisfying its achicveulent urotivation, it works fol too long a,ncl is in tlanger of over,ht:ating.
In this casc, thc robot can genel'atc a goal of pausing for an appropliate pcrioil irr or.<lel tcr
hL
t2
avoid arrv rlama,ge tci its comlronents. Such a loltot is atttonttrnous be<:ause its gclals arc llot
inposecl. but ale gettclatecl iu rcsponse to its etlvil'olllllcllt.
Altouonrous agents also pelccivc. ltut urotir.'a.tiorrs. as t'cl1 as goals, filter relevant asllct ts of
tlre erryilolruent. In thc schema belori'. the functiou. ott"tltrLtil,llxtr:r:iue is theu a 1llol'e torttltk'x
vrrrsiorr of arL agent's utillpe:r'r:r:iur:.b:uI thcv ale rc'laterl anci ntrst lte sirtce a1l al1tollorllolls
agerLt is still al ageut a,s shot'n irL the sclLcrna. Horver-t'r, that ri'hi<:lt an autollolllous itg('1It
is cu"T.utbLe: of per'<:civing at anv timc is indepcrLclent of its nrotivations. Irtclee<l. it ri'ill ahi-at's
lie ilclepcndent of goals arLrl rnotiva.tions. antl thelc'is consc<peutly rio crltrir-alt'tLt itr<r'cltst' irt
frrrrcr iorralit :' ro (.anl)ci'reirr
A t r"tctr nn
A ut. o r
r,
Ag erft P erce:pt,.s
r,ctu.s
A
rt t rt o r t s
q e n t,
AgerftPercept.s
u"ttt.ctutilLpt:r'ceiue: : P
u il
lp e
m
do
e
-
tt, o ur il,
lp
r c e iu
o" t
a"r
r: r
t"t,
Motirto}ioll
il
ow
r : e iu r:
r' r
lLt
s'[t
"
-
\
r
n
ct
t
r
:
P Gcto"l
r
tt
ct
t,iu rt'ti
t.t rt o.t.i ct n's
ct r t
-
Enuirorr,nt
ert,t - Vieut
s
j
The lext scirt:rna clcfirLcs thc at'tion-sclectiott firnctiotL aucl irLt'luclt-'s tltt'lltevitttrs s<lLt'ttla tlcfi'
rLitiorrs l,ot' Agr:rttAcl anrl Autr.nu.rrtc.tu,sAqr:tfi,. TlLc actiorL selectic-rrr iulctitlrL lol arL ilutollollLtills
agent is 1-rloclucerl at c\-et'\'instarLce ltr- the motivatious of tlic age'rtt. art<l is alt'at-s ;llt<1 orih'
ervcl applictl to thc rnotivatiorls of thc atlttlrtotnolrs agellt.
T AA
l
t
ft. o r t o
r
r,t r tr t
rn ct
ctnt,o
u,s
t t,s
A q erft, A r :t.
A rl r:n,t.
Arlr:rr,t,Act,
rrri.oo,cti ort
s : P M rtt.iprt,t,i.rtrt.
-
L
:
dom u,tfioo,r:t:i,orLs
o"
q
r: r
ft, o, r:t,it t r t,s
-
P GoaI
\ rttot:nro,t.u trts
(t,'t r,t,
o
r t,
r: t.'i
r,t
r
r"
s
rtt
j
o t.it
t
r
-
[1('11t
Ert,ui,nnr,rrrcn,t.
-
P A('t.i,ot]
t't,il t r t s
arL ir11to1t()lrro11s irsolrt
\ert. ri'e rlcfirLp the statc of
-
irL;,tt
t.rLr-iLotLrucrLt. arLtl
irLthlti0 tht'
Arlr:rtSt,o,t,e:. Arttr,trrr.trnr.nr,sAqert,t.Pet'ccpls arLcl Atrltnutrrt,tttr,sAge:rttAr:t. schcruits.
Au"t,
ct
n o t n o u,s A g
A rft o rt, o r rt o t
A
tr,t,
ort
c;
t"
s
A
e:r t t S t o"t
q e,n,t.
nz o rt s A q e
P
r:
e
r'ce, p t
s
rtt A r:t,
AgetttSto,te
utillrlo
4.3
:
urftoo.ctirln"s rrtcttiuttt,ir;ns gouls octrto'lpe:r'cept,s r:nrt'irortrrt'r:rfi,
Autonornous Agent Operations
As rvith objects and:r,gents. rvc rlefine rvhich of the vali:rbles that charactcrize thc atltottorttotts
irgent state rem:rirr unchangeci afte'r'a sct of actiorLs has lteen ptrlforrtietl bv tlLat agclt.
12
I r,
\
Autorutr
A
rr,t.
Arft
q
e:
ctrt rn t t,or n A
q
u
r
r.
orno
rr:
e
r:
iu in
r
-
'
r:u"1xtblr:of
p
A q erft S trt te
rr.rs t r"s
uA
o
('tLltl)(l\'(:i t'(' =
u.r
tt
t,tool:t,ior
o
ut'il lp
r: r t
r.c
Lt S
tat/
cepz,bleof
g t t" r : t.i r t r t
tt,t
rt t. S t u"t r :
s' -'yx:
('tLn
\a i1, c,'
l
=
u"r
t' t r
:
iu irt q u, cti rn t s
lLT ( it'(
(
=
o.r tt,
o
tt
iL lp
e:
r
r t : iu e
r,tt x t,t:ticttls
Norv tvc specilv tlLe operatiorL of arL arrtonornorrs agclrt per'lirlming its next sct of actigrrs irr
its ctrlleut etLvilonmettt. Notice that t,hilc no explicit rncntion is nrarle ol anv chanse irr
lllotivatiolls, thev rrtav cltaugc irL le'sponsc to charrges irr the environncnt. If thuv ckr chalgt'.
tlLcrr tltc ageut functtcttts'u,illpr:r'ceiur; tr:n<l o,ge-rtt,l,r:t.'irtn.* rvill also charLge. Fulthcr. nrotir-atiorLs
1IIa.\'gellcl'att'rLc'rv attcl diffet'c'ttt goals fol tlLe agent to purs11e. hL any of tlLc.sc <.ascs. t|c
charactelizirLg fc'atules of an agerlt ar'c iu flux so tirat an alltotlolrrolrs agcnt <'an itc legalriqrl
as a corttilLuallv t'c irrstantiatctl rtorL-attttxlornoLls agcrrt. hL this se1lsc. autollolrrotls il?(,trrs
a1C Pel'1IIil1I('1If aS t)1,1,,rs,',1 Io 11;rlLsir'1Lf 1r(J1l illltol}olriollS agclLtS (rvhich tnA\'l.c\.('1't t0 ltciilg
ob jccts ).
A
r t,t.
o rt
ct
rr r, o
r
A q rt i. E r tu I r i,
t,s
r :r r t, c t.
\Ert,u
\
A
r r,t.
o r r, o r r t rn
ltist,rtrtlt
-
r,,"
A
rl r: r tt. S t r t"t. r :
hist.ot'r1
-
r:ttu'i,r'rttrnt,r:tLt'
ui,l,l,1tr:rcr:'|ur:t
-
-
(rLtilld,ct)
r:.l.ftt:ti,tt,t,uut:t,irttt, r:tnt'i'r'ort,ttt,t:tt.t
LL,'iLLrlrt
rLtrtrtuti,l,l,perr:t:iut: rn,ot.,i,uo,t.iort,sl
o,r1r:rt,trt,cti.rtrr,st
-
ptt,<,s1tt:t't:t:pt..s'
--
u,'tLtoe,r:t,'i,orLs trr,ot.i,'ttrt,t.'iort.q'
ry11'y11.11.1r:t.tt,, t.'t
t.uit u/t.trr,r,tt.t' pt:r't'r.ittinqtt,r:t:ktrl.q
u,r:t,rr,rLl,1tr:rr:r:pt.*'
-'ut'ilhr:r'r:r:i,ur:'r1rxt"Ls'po,"."pr:rr:r:pt..s/
ob.jer:trt,r:tittrL,</= urlr:rft,rt,r:t,ir,nt,stqrtrt,/,s/o,t:t.tt,u,Lpr:r'r:t:7tts/
willrlri -
5
D
u"rttttu"r:tirtrrs rn,ot.'i.put.,iir,.c/ rlou,ls' o"t:t.rtrLltr:r,t:t:pt,s/ crruirotr.rt ;.:rtt,'
iscussion
TlLclc cxists a sruall lrorh'of rr'or'li tlLat prol'icles a sinilal r.icrv tcl that plcscntcrl lLelc. Fol
that r:h,u,ract.eri,zc autonourolls
s'r-stctns to sutlt<,r ''t1t:grcc". relatirLg to such factols as tvpe ancl nurnlrcr ol qoa1s. coruplcxitr..
irttclat'tiort, r'obttstrLcss. nttcl so on. Oril urork. in t'ontrast. takcs an a,bsolutc stancl o1r irutolr
trrrtv irt tlLat it citlrtlr'exists ol clocs rrot. X,Iolcor-t'r'" :ve de.firte: rvhat is lrcccssiu\- lirl a sr.stcru to
ltc autonornotrs in vet'r'prct'ist: tr:trns. and wc rlistinguislL cleallv betrveerL ob.jectrLcss. agorr(\.
itrL<1 a,tttcirLorttr-. OrLtr palticula,r' corlSeqllcnce of thc cliffelerLcc in viervs is that rvc allol a rocli,
fol exanple, to bc r:onsiclcrr:rl an a,gent i/it is bcing used for sornc l)llrpose. such a,s a harurncL
fol tett-pegs. Covt'igat'u arLcl Linclsay cleuy tlrt'ro<:k thc'qua,lity of autorrornr'Iecausc'it is
not goal-c1it'ecto(l. brrt ignclrer thc possibility of agenc\-. skipping ovcr arl inrportant palt of our
exa,rrt1rlc, Covligat'n anrl Lintlsav [2] clcs< r'ibe a set o1 1x'opelties
fra,mework.
14
TlLe notion of ntotil,trtion is not nerv, an<l has been usecl t:lsetvht:rt:. Sirtlon. for cxaruple. ta'kcs
urotiva,tion to be "that rithich controls attentiol at anv given time," And c'xlllortrs tht-' rcliition of ntotiva,tiori to infblmaticirL-plocessirrg bclLaviotrr. btrt fi'orn a, tlogrLitivt: pe|s1lt'ttilr' [1-l]
Morc recerLtlv. Slornan [16. 15] has elabolatecl orL Sirrron's tt'otk, shorvirtg ltorv motivations
aLe 1t'|eva1t to crruotions antl tlLe cler-clopnrcnt of a (:{jtt}putational thtrolv of ruiu<1. OtlLtlls
.
1secl ltotir.'atio1 a1r1 r'eia.tc<l rrotiorLs in developing comltutationai alchitectules for atr
to1ol1o11s lqelrrs s1clL as tlte rnctt,iur:sof Ncl'rnarL a,u<l Long [9] . and lltc cc.tn,u:rtrsof X{offat and
Fliicla . \\.hat is rLes, about tlLt: ctrllent t'olk is the role of rrrotivation irr tlefinirLg autortorrtt'.
layc
[8]
6
Conclusions
tlLe pt'r:r'io1s sectirtns. nt: havc constntctcd a foltna,l specification rvlti<'h icle'rLtific's arLd
cha12<tterizcs those eltitic.s that alt: callcti agerrts artci atrtonoulous a,gorts. TlLe rvolii is rLot
blsecl ot1 alry existilg classilications or notions lieca,ttse thcle is llo cons('llsns. Reccrtt 1)a1)crs
4t:fi1e agents irr rvil<ll_v cliffrrrent rvavs if at all. and this nralies it extlt:rnely <lifHcrrlt to llc cxlllicit
altstrt t[cil 1atu1e arLrl flrLt'tionalitv. The taxonorllv gi\-e11 ht're selves scvr:r'al 1)111'Pos(]s:
Iu
plccise tlcfinitiorts fcll ollj<'r'rs. agents arLcl alrtorttlttlcrtls as.lLts tlL;rt
a1191' a lrctter ulrlet'stanrling ol t1te'furtctiorLalitv of diffelent svstcrlrs.
r Ir
11'oyicles r:lt,a1
arLc1
o It explicates thost'lactols thirt alr'rlcccssar\'lbt'agencv
ancl atrtonorllr'.
is srifficir:rLtlv altstlact to covol't1Lo garrtut of agcrtts. harthvale anrl softri-iirt'. irrtollig<'rLt
ancl unilteiligeut. etc.
It
It
allcx1s 11r'thcr.|,r'cls of specificatiorL
to lrc' atlrlt'd to tle'sclibc'llalticrtlaI ascrLt tlcsiurLs
an<1 architt'ct111'('s.
thrct' < 1ir.si's ol erLtitrr, olt.'it,r:t,s. tt,r1t:rtl,s rttttl rtttt,r.trL(nrt,tt,Lr,s rLrlr ttt.s. Thc tlistinctions bc'trr'ec'tI tlIelII ar(' :i1II1)1c lrtrt stl,tLg l,tL'1 ' 1":tt '
TlLc f1alrervor'li plovicle's arL irupoltaut lrasis lirl lr'Ii:r'r'rrce. \\tc'carL clas"ifv lrotlL lLtltu;,tt ir tL'l
altificial agelrts c<|ra11r' $'eii. ClonsirlcI tlLc lr'latiorLslLiP of ;r llrogIalIllll('1't() a 1)1'oglrlrtt. PIt'
g'arrrs a1c a1s-ar-s tlcsiglcrl to satislr'goals. lmt tht'se'goals ale liilelv cxPlir:it ol'itlrli'1tl lri'
i1clepe1clcntl1. of the prograrnrrrel. The ploglarns lack goal-gcrLeliiting motir''ittiorLs.
'ro<lifiecl
liut ca1 bc ascliltecl gcials. In this lcspe<'t. tht'1,'arc agerlts. Proglarnrlrtlrs tvpicallv tlcvelolr
progr-ans at.colclirLg to sevela,l rnotivations whiclL clctelmirLe horv the pt'ogl'aln is r:onstluctcrl.
Tir'e iirLcl cffg1t lnst 6c |alznLcerl against cost. casc of usc. sinrplicity. functiorLalitv arLtl otlLcr'
facto's. proglarrplels colsiclcl thcse factols il dcte.r'rninirLg thc ilesign of plogratrrs art<1 irt tltt'
goal or.goals of pr.ogr'?r1lls. Progla,ururels can <:lLangc thc goa.ls of p-,.'ogra,rus lrv utodilr'iug ccidc
if <lesilccl. arLcl carL rnorlii'v tlLeir orvn goals to strit cilt'rrnrstitnt:es. hL this I'cs1)c('t. 1)l'ogf illlllII('1 s
Irr
srrrrrrrrlr.J-" \\-(\ ha'u-c <lefirLt't1 arrrl slrccifi<'<l
al'c
a11to1Io11I011s ?igcrnts.
Tire clifferelct' beti,r,,ce1 thesr: kinrls of pt'ogral]ts :rs agents antl urri:h Lcceut use rlf tlttl telrnr
is that t[e relatiolship ltettveen thc user (or p1'og1'autlller') and the pt'ogranl has llecorntr
explicit. Softrva,rc agonts assist usels. Thev adopt tlic goals of thc users in tire tasks that
they pe1fo11r.. \\rlLethel ol rLot they arc. ?rutollonous cit'pert<ls otr thc abilitv of thc ageilts tt't
flrrctiol inclepcncleltiy of those users, ald to modifv their goals iu relatiol t<l cilc.trursta'nces'
Tlis paper ha,s rna,ilt: explicit the relationships tha,t havc previously been iurplicit actoss the
15
lloalcl in the vrist t'ange of rvorli on agencv ancl autorrourv.
orr rvhich to build.
an<1
provicies a stlotlg for''ral Sasc
Ottt'as1rt'ct rlot it<ltilessecl httle. horvever. is exar:tlv ltotn goals alc gelclatecl fi'orrr lrotir.-atiorLs.
TlLis is a clifficrrlt issrtc'. but tvclr'li is ptciglessirLg orL c1c'r.'e.lopirLg goal-gclelatiorL r1.c1.uisrrrs"
irr<'lrrclirlg tlffot'ts rlesclibc<1 in tht: r'elatc<1 rvor'li scctiorr abor-e. TlLe nqxt stage of tlis ri-.rli is t.
firl'trtalize a ntcitltrl of goal generation in the sirlnc \\-zrv as the 1r anervorli |iis 5cerL c.ust'rr.t.rl
lLt'r'c. <lt'velopirLg a cornPlete alchitectule fol autononrolls agclrts.
References
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l7