CTC6, Educational Session 603
Artificial Intelligence in the Legal Environment
A Legal Reasoning System on the
Contract Law (CISG)

Hajime YOSHINO

Professor of Law

Meiji Gakuin University Faculty of Law

1-2-37 Shirokanedai, 108-8636 Tokyo

yoshino@law.meijigakuin.ac.jp

http://www.meijigakuin.ac.jp/~yoshino
1
Hajime Yoshino:
Hajime Yoshino:
Contents
Object
this paper of Logical Jurisprudence
Birth
and of
Development
(Case,
query and
solution) and Jurisprudence for it
(LJProblem
as a front
for science
of law)
of Sound
 Necessity
1.a applied
Introduction
LJ
as
logic toand
lawEfficient Jurisprudence
Development
of
Logical
Jurisprudence
(LJ
as
a
realistic
theory
of
law)
 2. Case, query and solution
the concept of law in LJ
 3. What
Primitives
of LJ is Logical Jurisprudence
Legal
in termssentence
of LJ
 4.Reasoning
Basic legal
concepts and



structures
5. Logical structure of contract law
regulating changes of legal relations
6.Legal reasoning system on CISG,
LES-5
7. Conclusion
2
yoshino:
l This
structure
paper legal
presents
knowledge
at first a hypothetical legal problem, queries on
ces
it such
and the
resolutions
resolutions.
as
It shows then what LJ is and it introduces
basic concepts of legal sentences according which LJ enables us to
l constitute
based on Logical
a logical system of law. On this basic model, this paper
ationship
clarifiesbetween
the logical
legal structure of law focusing on contract law which
ces
regulates
that regulate
change the
in legal relations. This paper refers to LES5 as a
definitive
realization
role.
of legal
The model
reasoning develop by us on the basis of LJ. It
s concludes
Conventionsuggesting
on Contracts
further
for possibilities of LJ.
(CISG) to develop a
. The deductive structure of
o that appropriate answers
ut the legal state of affairs
f the application of CISG
1. Introduction
What is a legal reasoning system
of law as well as AI in Law
n be justified as a
together with relevant
ffairs changes according to
a clarified logical model of
o deduce the changes among
rom the beginning to the end
3
Tasks of Judges and AI in Law

It is important task for a judge to decide what legal
judgment should be made for a given case and to
show how the judgment is justified.

A legal reasoning system as an artificial
intelligence of law, which infers the legal state of
affairs as conclusion from law and the facts of a
case and shows clearly the deduction process, will
be, therefore, a useful tool for the practice of
judges.
4
Several approaches to legal reasoning
system
• 1 rule based legal reasoning system
• British Nationality Act (Kowalski & Sergot),
• LES-2, LES-3 (Yoshino)
• 2 case based legal reasoning system
• HYPO(Ashley),
• GREBE(Branting)
• 3 hybrid reasoning system
• CABARET(Rissland & Skalak)
5
Limitations of the approaches
• Partial, narrow, separated legal subjects
• The whole deductive system of law is unclear
• The changes of legal relations in terms of time
progress have not been enough clearly
formalized
• Lack of legal theoretical basis
6
What is necessary to construct correct
Legal Reasoning systems

In order to construct legal reasoning system it is necessary first to
clarify the logical structure of the law system as a whole.

The legal state of affairs, which refers to the status of legal relations,
changes according to the chronological progress of an event over time.
We therefore must clarify such a logical model of law that enables us
to deduce changes of legal relation according to time, regardless of any
time point in given events from the beginning to the end.

The systematization of law, i.e., to present the law as a deductive
system, has long been a central theme of legal theories, but previous
studies did not succeed in presenting a legal system as deductive.


We need a sound and powerful logical theory of law.
7
The objectives of this paper








Logical Jurisprudence has succeeded in clarifying the logical structure
of the law system in the above sense and on its basis we have
developed a legal reasoning system entailing knowledge base of the
CISG (United Nations Convention on Contracts of the International
Sale of Goods).
Our aim here is to present the essence of the clarification of the logical
structure of contract law system by focusing on the CISG.
In this paper I would like to introduce you
what is Logical Jurisprudence,
how the structure of contract law is to be clarified,
what structure it has and
how we developed LES-5, a legal reasoning system of CISG and
How it works in fact in demonstration.
8
Contents







1. Introduction
2. Case, query and solution
3. What Is Logical Jurisprudence
4. Basic legal sentence concepts and
structures
5. Logical structure of contract law regulating
changes in legal relations
6.Legal reasoning system on CISG, LES-5
7.Conclusion
9
2. Case, query and solution

Case 8f
( 1 ) On April 3rd, 1997 A (Anzai) , a farming machine
maker in New York, sent a letter to the branch office
in Hamburg of B (Bernard), a Japanese trading company.
The content of the letter was: A sells B a set of
agricultural machines which is composed of a tractor
and a rake and the price of the tractor is $50000; A
delivers the machine to B by May 10th, B must pays the
price of the system to A by May 20th and the
agricultural machinery will be carried by an American
freight vessel.
( 2) On April 8th, the letter reached the letter box of
B’s branch office in Hamburg.
( 3) On April 9th, B made a telephone call to A. “I
accept your offer. However, I want you to carry the
machine by a Japanese containership”
( 4) On May 1st, A delivered the farming machine to a
Japanese container ship at the port of New York. 10
( 5 ) On May 31, the machine was delivered to the branch
office in Hamburg.
( 6) On June 5th, B examined the machine.
( 7) On May, 10th B paid the price to A.
( 8) On August 10th, the machine proved to be operating
out of order because of a bad connection gear. B
immediately gave the notice to A specifying the
nature of the lack of conformity.
( 9) On September 1st, B asked A to repair the lack of
conformity of the machine within one month. A did
not repair the non-conformity until 1 October.
( 10) On October 10th, B declared the avoidance of the
contract.
( 11) On December 10th, A recovered the damage and B
restituted the machine delivered by A.
( 12) On December 20, A restituted the price paid by B.
11
Queries










At each of the points of time indicated below, what is
the legal relation that exists between A and B?
1: April 5th
2: April 15th
3: May 5th
4: August 15th
5: September 15th
6: October 5th
7: November 15th
8: December 15th
9: December 25th
12
CISG Articles









The following articles of the CISG apply to the case:
Article 15(1) An offer becomes effective when it reaches the
(2) An offer, even if it is irrevocable, may be withdrawn
withdrawal reaches the offeree before or at the same time
offer.Article 16(1) Until a contract is concluded an offer
revoked if the revocation reaches the offeree before
dispatched an acceptance.
Article 18(2) An acceptance of an offer becomes effective
moment the indication of assent reaches the offeror. … .
offeree.
if the
as the
may be
he has
at the
Article 23
A contract is concluded at the moment when an acceptance of an offer
becomes effective in accordance with the provisions of this
Convention.
Article 31
If the seller is not bound to deliver the goods at any other
particular place, his obligation to deliver consists:
(a) if the contract of sale involves carriage of the goods - in
handing the goods over to the first carrier for transmission to the
13
buyer;









Article 38
(1) The buyer must examine the goods, or cause them to be examined,
within as short a period as is practicable in the circumstances.
Article 39
(1) The buyer loses the right to rely on a lack of conformity of the
goods if he does not give notice to the seller specifying the nature
of the lack of conformity within a reasonable time after he has
discovered it or ought to have discovered it.
Article 45
(1) If the seller fails to perform any of his obligations under the
contract or this Convention, the buyer may:
(a) exercise the rights provided in articles 46 to 52;
(b) claim damages as provided in articles 74 to 77.
(2) The buyer is not deprived of any right he may have to claim
damages by exercising his right to other remedies.
14








Article 46
(1) The buyer may require performance by the seller of his obligations
unless the buyer has resorted to a remedy which is inconsistent with
this requirement.
(2) If the goods do not conform with the contract, the buyer may
require delivery of substitute goods only if the lack of conformity
constitutes a fundamental breach of contract and a request for
substitute goods is made either in conjunction with notice given under
article 39 or within a reasonable time thereafter.
(3) If the goods do not conform with the contract, the buyer may
require the seller to remedy the lack of conformity by repair, unless
this is unreasonable having regard to all the circumstances. A request
for repair must be made either in conjunction with notice given under
article 39 or within a reasonable time thereafter.
Article 49
(1) The buyer may declare the contract avoided:
(a) if the failure by the seller to perform any of his obligations
under the contract or this Convention amounts to a fundamental breach
of contract; or
(b) in case of non-delivery, if the seller does not deliver the goods
within the additional period of time fixed by the buyer in accordance
with paragraph (1) of article 47 or declares that he will not 15deliver
within the period so fixed.
Solutions









1) On April 5th, there is no legal relation between the seller A (Anzai) and
the buyer B (Bernard)
2) On April 15th, A has a duty to deliver the farming machine to B by May
10th and B has a duty to pay the price $50,000 to A by May 20th, while B has
right to require A to deliver the goods to B and A has the right to require B
to pay the price to A by May 10th.
3) On May 5th, B has a duty to pay the price $50000 to A by 20 May, while A
has right to require B to pat the price to A by 10 May.
4) On August 15th, A has a duty to recover the damage, while B has right to
claim A the damage and B has right to require A to repair the machine.
5) On September 15th, A has a duty to recover the damage and a duty to repair
the machine, while B has right to claim A the damage and B has the right to
require A to repair the machine which is restricted to exercise.
6) On October 5th, A has a duty to recover the damage and a duty to repair
the machine, while B has right to claim A the damage, B has right to
require A to repair the machine and B has a right to declare the contract
avoided.
7) On November 15th, A has a duty to recover the damage and a duty to
restitute the price paid by B, and B has a duty to restitute the machine
delivered by A, while B has a right to claim A the damage and a right to
require A to restitute the price, and A has right to require B to restitute
the machine.
8) On December 15th, A has a duty to restitute the price paid by B, while B
has right to require A to restitute the price.
9) On December 25th, there is not legal relation between A and B on the
16
contract.
Changes of legal Relationships (Fig. 3a)
nges
＜
＜
f
en
Q
A
L
t
u
n
e
s
e
s
g
＞
r
w
a
u
l
y
e
e
r
r
・
Ａ
・
Ｂ
Ａ
４
／
５
T
hquery
e r e
i s
l e g a l
r e l
(1)
reaches
b e -
４
O f
／
f e
８
r
to
B
o
m e s
v a l i d
O f f e r
e f f e c t
i s
i v e
c
c e p t .
b e ptance
４
／
９
o m e s
v a
l i d
hes
to
A
d u
t
y
t
o
r
ig
ht
t
o
r ed
q
e
l it
v e
r
the
v ed
r
h
e
g
query
引
４
／
1
5
B
m
a
y
d
u
t
y
o
t
r
i
g
h
t
(2)
t
o
r
e
q
A
h
a
s
a
渡
r
e
q
u
i
r
e
t
o
p
a
y
th
e
p
t
h
e
p
r
d u
t
y
t
o
す
A
Am a
ty
o
d
e
l
i
v
e
r
義
r
e
B
q
u
h
５
i
a
r
s
e
a
d
e
l
i
v
e
r
t
h
e
務
d
u
B
t
月
y
t o
t
h
e
g
o
o
d
s
が
t
p
o
a
y
p
1
a
0
t
y
h e
g
o
o
d
s
s
over
the
あ
p r
t
i
h
日
c
e
e
t o
o
the
first
る
p r
A
i
ま
c
b
e
y
５
／
１
r
Japanese
M a
b
y
y
で
1 0 .
iner
M a
に
y
Ship
1 a
0 s
t h a
.
A
h
query
d
u
t
y
t o
r
ig
h
t
o
p
d u
t
y
t
o t
５
／
５
t
h
e
p
r ir
c
t
h
e
p
(3)
d e l i v e
r
h e
g o o d s
w
the
h i c h
price
５
／
c o n f1
o0
r m s
t o
t h e
oods
is
c
o ／
n t3
r1
a
c t
５
ered
to
amines
６
／
５
goods
B
17
a
c
h
i
repaithmcn.Bsduyo
AhasdutyorecvmgfB.
m
BmaycliAthedg.
e
is
opera
o
f
o
r
der
8 ／ 1 0
o
A
speci
of
t
he
la
m
y
d B
u trig
y a
t o
r
ht
to
r
r
e
i
r
e
A
fo
m
i
t
y
to
r ep
vr
e q
r u
t
h
e
d
t
o
r
e
p
a
i
r
８ ／ 1 5
query
rig
ht
to
c
t h
e
(
4)
da
ma g
n
e
.
９
／
１
r
c i
s
e
o
f
c l
A
h
a
s
a
t
o
r
e
p
a
i
r
t
o
r
e
p
a
i r
.
d
u
t
y
t
o
thin
one
m
d e l i v e r
t h e
g o o d s
w h i rig
c h
ht
to
re
d
u
t
t
o
r
g
h
t
cT
oh
ne
f y
or
ri
m
s
to
r
ep
t
h
e
m
a
c
h
q
u
e
r
y
t
o
c
l
a
i
m
t
o
t
h
e
(
r
es
tr
ic
９ ／ 1 5
t
o
r
e
p
a
i r
c o
d
n
u
t
t
r
y
a
c
t
t
o
r
rig
(
ht
5
)
to
c
da
ag
v e r i s
t h
em
d
r e s t r i c t e d
i
onal
peri
1 0 ／ １
pi
r
e
d
.
d u t rig
y
t o
r
ht
to
re
B
m
a
y
B
m
a
y
to
rep
t
h e
m
a
c h
q
u
e
r
y
r e
q
u
i
r
e
A
d
e
c
l
a
r
e
d
u
t
y
t
o
r
rig
ht
to
c
t
o
r
e
p
a
i
r
1 0
／
５
t
h
e
(
6
)
da
m
a
v
e
r
t
h
e
d
t h
e
m
a
c
h
i
n
c
o n
t
r
a
c
t
rig
ht
to
a v
o i
d e
d d
.
contr a ct
the
a
cont
1
t0
o／
d
1
e
0
c l a r e
oided.
A
h
B
a
s
m
a
y
d u t
y
t
o
r
cla
im
to
r
e
a
d
c
u
l
t
a
y
i
m
t
o
A
B
the
p
t
u
t
e
t
h
e
At i
mt
a
y
r e s
t
u
o
t e
q
u
e
r
y
d
u
t
y
t
o
cla
im
to
r es
c
B
l
a
h
i
a
m
s
e
B
s
t
i
t
u
t
e
1 1 r
／
1
5
A
the
m
a
ch
t
u
t
e
m
a
(
7
)
B
d
t
u
o
t
y
t h e
ta
h
p
e
r
i
p
c
r
e
i
c
e
r
e
d
s
u
t
t
i
t
y
t
o
u
t
t
o
e B
r
rig
ht
to
c
p
a
p
i
a
d
i
d
b
y
b
y
B
da
m
a
r
v e
et
s
r
tt
hi
t
e
t
h
u
e
t
e
d
e
d
h
e
d
a
m
1 2
／
1
0
m
aA
c e
ht
ih
n
e
e
d
t
h
m
ac
d em
la
ic
vh
ei
rn
ee
d.
1 2 ／
1
5
d
b
u
y
t
y
A .
t o
cla
im
to
r es
q
u
e
r
y
A
the
m
a
ch
t
u
t e
m
a
(8
)
i
tuted
t
he
1 2 ／ 2 0
paid
by
B.
q
u
e
T h
e
r
er y
i
1 2
／
2
5
l e g a l
r
e l
(9
)
18
Contents







1. Introduction
2. Case, query and solution
3. What Is Logical Jurisprudence
4. Basic legal sentence concepts and
structures
5. Logical structure of contract law regulating
changes in legal relations
6.Legal reasoning system on CISG, LES-5
7.Conclusion
19
3. What Is Logical
Jurisprudence (LJ)

Concept of logical jurisprudence
• Logishe Rechts Lehre
• A developed form of “legal logic”
(Juristische Logik)
• Naming is done by Hajime Yoshino.
20
primitives:

“sentence,”
• LJ consider that norm as a meaning does
not exist.
• LJ starts from sentences.

“validity” of sentence
• legal validity as legal truth

“inference rule.”
• Modus Ponens: （（A →Ｂ）＆Ａ）→Ｂ
21
Legal Reasoning as a development
of legal sentences (Fig.1)
Rule
al
Sen
Purpo
of
La
Princi
hard
Statute
DGtandbkfliscovery
Justifcaon
erpretati
general
Set o
mon
Sense
gal
Conce
rpretatio
soft
concrete
Set
ct
Senten
nfirmed
f
Set
scribed
F
Set
Events
dgement
l
S
Concre
Conclus
Jutic
22
Two types of legal Reasoning

Reasoning of legal justification
• Modus Ponens: （（A →Ｂ）＆Ａ）→Ｂ

Reasoning of legal discovery
• Abduction and
• induction
• falsification： Modus Tollens: （(Ａ→Ｂ）＆～
Ｂ）→～Ａ
23
Legal Reasoning Structure (Fig.1)
Rule
al
Sen
Purpo
of
La
Princi
hard
Statute
DGtandbkfliscovery
Justifcaon
erpretati
general
Set o
mon
Sense
gal
Conce
rpretatio
soft
concrete
Set
ct
Senten
nfirmed
f
Set
scribed
F
Set
Events
dgement
l
S
Concre
Conclus
Jutic
24
Contents







1. Introduction
2. Case, query and solution
3. What Is Logical Jurisprudence
4. Basic legal sentence concepts and
structures
5. Logical structure of contract law regulating
changes in legal relations
6.Legal reasoning system on CISG, LES-5
7.Conclusion
25
4. Basic legal sentence
concepts and structures




Legal rule and fact sentences
Legal object and meta sentences
Legal elementary and complex
sentences
Existence of an obligation and the
validity of the legal object sentence
(Fig.2)
26
Legal elementary and complex
sentences

Elementary legal sentence
• the smallest unit of legal sentences.
• "one must drive a car under 100 km
/hour on a highway”
• “A may require B to pay the price of
$10000.”
27
Legal rule and fact sentences

Legal rule sentences:
• “∀X{a(X) ← b(X)}”.
• legal consequence ←legal requirement
• “∀X{become_effective(offer(X,A),T) ←
reach(offer(X,A),offeree(B,X),T)}”

Legal fact sentences:
• “b(x1)”.
• reach(offer(o1,anzai),offeree(bernard,o1),
4_05).
28
Legal elementary and complex
sentences

Elementary legal sentence
• the smallest unit of legal sentences: An element of
contract or statute
• "one must drive a car under 100 km /hour on a highway”

Complex legal sentence
• a sentence named for a group of legal sentences
• code, contract, a section of statute, an article
• “the United Nations Convention on Contracts for the
International Sale of Goods,”
• “a contract for sale of a farming machine between A and
B on October 8. 1997.”
29
Legal object and meta sentences

A legal object sentence describes
obligations of a person
• “B must pay A the price of $10000”

A legal meta sentence prescribes
about legal sentences
• It describes the validity of a legal sentence.
• “(1) This Convention applies to contracts of sale
of goods between parties whose places of
business are in different States : (a) when the
States are Contracting States; or … ”
30
Obligation of persons as ultimate
normative state of affairs

Law ultimately prescribes the obligation of persons.
People’s conduct is ultimately regulated by
obligations given by object sentences.

What is that legal obligations exist ?

31
Obligation and the validity of legal
object sentence
ce
ob
l
o b j e c
t
n
0
o
o
i
s
vb
al
li
i
i
g
s
a
o
i
b
o
l
n
i
v
t
e
1
nt
t
1
e
u
c
r
o
n
m
s
e s
u p
v
X
i
s
"
X
i
s
o
b
l
i
g
a
l i g a
t
o
r
i
l
t
T
o
i
o
n
g
r
a
y
X
t
o
e
r
i
s
v
a
l
i
i
i
s
g
a
o
t
b
il
oi
n
v
t
e
2
n
t
2
s
t
e
t
r
e
m
r
i
m
ni
an
t
l
o bo
jb
el
c
t
3
n
o
i
s
v a
l
ve
ec
nt
ta
ss
m
e
t
32
Contents







1. Introduction
2. Logical Jurisprudence
3. Basic legal sentence concepts and
structures
4. Case, query and solution
5. Logical structure of contract law
regulating changes in legal relations
6.Legal reasoning system on CISG, LES-5
7. Conclusion
33
5. Logical structure of contract
law regulating changes in
legal relations



5.1 Legal rule sentences deciding that
legal sentences are valid.
5.2 Logical structure of contract law
deciding accrual of obligation
5.3 Logical structure of contract law
deciding termination of obligations
34
5.1 Legal rule sentences deciding
that legal sentences are valid.

Fundamental legal meta rule sentence is valid
to confirm that legal sentences are valid:

(0) A legal sentence S is valid at the time T
←
S becomes valid at time T1 before T ＆
S is not terminated until T


• The validity of this fundamental legal meta rule is
described as a fact. Or it is presupposed that it is
always valid.
35
5.2 Logical structure of contract
law deciding accrual of obligation

The accrual of validity of a complex
legal sentence follows the accrual of
validity of elementary legal sentences
which belong to it.

(r01) become_valid(ES,G,T) <element_complex_sentence(ES,CS)&
become_valid(CS,G,T)

36
Changes of legal Relationships (Fig. 3a)
nges
＜
＜
f
en
Q
A
L
t
u
n
e
s
e
s
g
＞
r
w
a
u
l
y
e
e
r
r
・
Ａ
・
Ｂ
Ａ
４
／
５
T
hquery
e r e
i s
l e g a l
r e l
(1)
reaches
b e -
４
O f
／
f e
８
r
to
B
o
m e s
v a l i d
O f f e r
e f f e c t
i s
i v e
c
c e p t .
b e ptance
４
／
９
o m e s
v a
l i d
hes
to
A
d u
t
y
t
o
r
ig
ht
t
o
r ed
q
e
l it
v e
r
the
v ed
r
h
e
g
query
引
４
／
1
5
B
m
a
y
d
u
t
y
o
t
r
i
g
h
t
(2)
t
o
r
e
q
A
h
a
s
a
渡
r
e
q
u
i
r
e
t
o
p
a
y
th
e
p
t
h
e
p
r
d u
t
y
t
o
す
A
Am a
ty
o
d
e
l
i
v
e
r
義
r
e
B
q
u
h
５
i
a
r
s
e
a
d
e
l
i
v
e
r
t
h
e
務
d
u
B
t
月
y
t o
t
h
e
g
o
o
d
s
が
t
p
o
a
y
p
1
a
0
t
y
h e
g
o
o
d
s
s
over
the
あ
p r
t
i
h
日
c
e
e
t o
o
the
first
る
p r
A
i
ま
c
b
e
y
５
／
１
r
Japanese
M a
b
y
y
で
1 0 .
iner
M a
に
y
Ship
1 a
0 s
t h a
.
A
h
query
d
u
t
y
t o
r
ig
h
t
o
p
d u
t
y
t
o t
５
／
５
t
h
e
p
r ir
c
t
h
e
p
(3)
d e l i v e
r
h e
g o o d s
w
the
h i c h
price
５
／
c o n f1
o0
r m s
t o
t h e
oods
is
c
o ／
n t3
r1
a
c t
５
ered
to
amines
６
／
５
goods
B
37
Fig. 4
o n t
n
t
r
a
c
i
N
(
f a
l
s
e
bo
e
f
o
r
e
s
(
t
r
u
e
)
A
1
B
B
]
(
f a
l
s
e
tN o
i
s
i
n
s
(
t
A
1
s
r
u
e
)
B
C
]
t
h
e
A
1
B
C
]
( f a
l
s
e
iN
mo
e
h
a
s
o
n
o
t
r
a
fN o
t
(
i
s
T
e
(
t
h
d
(
r
Ｔ
Y
e
f
a
l
e
e
c
)
o
a
t
N
o
f a
l
s
e )
u e )
＝
s
s
c
h
(
t
r
Ｔ
u
e
)
A
[
1
~
B
3
]
A
A
1
c
S
o
m
b
e
e
s
c
o
v
38
Fig.5
nt
o
f
a
S
n
o
i
s
y
e
s
a
n
c
in
do
y
e
e
a
s
n t
t
r t
a h
c
c
c l
o u
n d
c e
39
5.2.2 The accrual of the validity of a
legal object sentence by exercising the
right





The accrual of validity of the elementary legal sentence
by itself can be regulated.
(3AA2) "A legal sentence 'X has an obligation to do Z'
becomes valid at time T,
if a legal sentence 'Y has a right to require X to do Z'
is valid, and Y exercises the right to require X to do Z
at time T.”
(rCISG46): “The buyer has a right to require the seller
to remedy the lack of conformity by repair” becomes
valid,
if the goods do not conform with the contract.
40
Changes of legal Relationships (Fig. 3b’)
a
c
h
i
Bsduyo
AhasdutyorecvmgfreBp.aithmcn.
m
BmaycliAthedg.
o p e
i s
d e r
r
o
f
1 0
8 ／
s p e c
A
o
l
e
h
t
f
o
y
a
m
B
o
t
y
t
d u
o
t
t
igh
r
e
r
i
u
q
e
r
y
t
i
m
r
o
p
e
r
o
t
d
e
h
t
r
e
a i
p r
ee
r
o
t
5
1
／
８
y
u
q
o
t
t
gh
i
r
e
h
t
)
4
(
a
am
d
n
e
９
c
o f
s e１
i ／
i
a
p
e
r
o
r
i
a
p
e
r
o
h i n
o n e
r
o
t
t
igh
r
r
o
t
y
t
u
h
g
i
r
e
h
T
p
e
r
o
t
c
a
m
e
h
t
y
r
e
u
q
m
i
a
l
c
o
t
c
i
r
st
e
r
(
1 5
／
９
a
p
e
r
o
t
o
t
y
t
u
d
o i
)
t
5
t
(
gh
i
r
ama
d
s
i
d
e
h
t
e r
e s t r i c t e
o
0
i
u
p e
l
a
n
１
／
.
d
e
r
r
o
t
y
tr
r
o
t
t
igh
a
y
ay
m
B e m
p
e
r
o
t
c
a
m
h
t B
y
r
e
u
q
e
r
i
r e
e
r
a
l
c
eu
dq
o
t
y
t
u
d
o
t
t
gh
i
r
i
a
p
e
r
o
t
e
h
t
５
／
0
)
6
(
a
m
a
d
d
e
h
t
r
e
i
h
c
a
m
e
h
t
c
a
r
t
o n
c
d
o d
t
t
gh
i
r
e
d
i
o
a v
ac t
r
c on t
t h e
a
c o n
l a r
0
c
1
d e
0 ／
o
o i d e d .
y
a
s
m
a
h
B
A
r
o
t
y
t
u
e
r
o
t
m
ai
l
c
A
o
t
m
i
y
a
t
l
u
c
d
p
e
h
t
B
e
h
t
e
t
u
t e
o
u
t
e s t i t
y
r
e
u
q
o
t
y
t
u
d
s
e
r
o
t
m
i
la
c
t
u
t
i
t
B
s
e
r
5
1
／
1
c
a
m
e
h
t
A
a
m
e
t
u
t
)
7
(
c
e
i
c
r
i
p
p r
h e
e
t
h
o
t
y
t d
u
d
o
t
t y
gh
i
r
B
b
y
b
i
d
a
i
p
a
a
am
d
d
e
t h
e r
1 0
2 ／
5
1
／
2
o
t
y
t
u
dc
es
r
o
t
m
i
la
y
r
e
u
q
c
a
m
e
h
A
a
m
e
t
ut
t
( 8 )
41
5.3 Logical structure of contract
law deciding termination of
obligations

The validity of elementary legal sentence is
terminated if the complex legal sentence is
terminated.
42
Changes of legal Relationships (Fig. 3b’)
a
c
h
i
Bsduyo
AhasdutyorecvmgfreBp.aithmcn.
m
BmaycliAthedg.
o p e
i s
d e r
r
o
f
1 0
8 ／
s p e c
A
o
l
e
h
t
f
o
y
a
m
B
o
t
y
t
d u
o
t
t
igh
r
e
r
i
u
q
e
r
y
t
i
m
r
o
p
e
r
o
t
d
e
h
t
r
e
a i
p r
ee
r
o
t
5
1
／
８
y
u
q
o
t
t
gh
i
r
e
h
t
)
4
(
a
am
d
n
e
９
c
o f
s e１
i ／
i
a
p
e
r
o
r
i
a
p
e
r
o
h i n
o n e
r
o
t
t
igh
r
r
o
t
y
t
u
h
g
i
r
e
h
T
p
e
r
o
t
c
a
m
e
h
t
y
r
e
u
q
m
i
a
l
c
o
t
c
i
r
st
e
r
(
1 5
／
９
a
p
e
r
o
t
o
t
y
t
u
d
o i
)
t
5
t
(
gh
i
r
ama
d
s
i
d
e
h
t
e r
e s t r i c t e
o
0
i
u
p e
l
a
n
１
／
.
d
e
r
r
o
t
y
tr
r
o
t
t
igh
a
y
ay
m
B e m
p
e
r
o
t
c
a
m
h
t B
y
r
e
u
q
e
r
i
r e
e
r
a
l
c
eu
dq
o
t
y
t
u
d
o
t
t
gh
i
r
i
a
p
e
r
o
t
e
h
t
５
／
0
)
6
(
a
m
a
d
d
e
h
t
r
e
i
h
c
a
m
e
h
t
c
a
r
t
o n
c
d
o d
t
t
gh
i
r
e
d
i
o
a v
ac t
r
c on t
t h e
a
c o n
l a r
0
c
1
d e
0 ／
o
o i d e d .
y
a
s
m
a
h
B
A
r
o
t
y
t
u
e
r
o
t
m
ai
l
c
A
o
t
m
i
y
a
t
l
u
c
d
p
e
h
t
B
e
h
t
e
t
u
t e
o
u
t
e s t i t
y
r
e
u
q
o
t
y
t
u
d
s
e
r
o
t
m
i
la
c
t
u
t
i
t
B
s
e
r
5
1
／
1
c
a
m
e
h
t
A
a
m
e
t
u
t
)
7
(
c
e
i
c
r
i
p
p r
h e
e
t
h
o
t
y
t d
u
d
o
t
t y
gh
i
r
B
b
y
b
i
d
a
i
p
a
a
am
d
d
e
t h
e r
1 0
2 ／
5
1
／
2
o
t
y
t
u
dc
es
r
o
t
m
i
la
y
r
e
u
q
c
a
m
e
h
A
a
m
e
t
ut
t
( 8 )
43
5.3 Logical structure of contract
law deciding termination of
obligations

The validity of elementary legal object
sentences is terminated when the obligation is
fulfilled.
44
Changes of legal Relationships (Fig. 3a)
nges
＜
＜
f
en
Q
A
L
t
u
n
e
s
e
s
g
＞
r
w
a
u
l
y
e
e
r
r
・
Ａ
・
Ｂ
Ａ
４
／
５
T
hquery
e r e
i s
l e g a l
r e l
(1)
reaches
b e -
４
O f
／
f e
８
r
to
B
o
m e s
v a l i d
O f f e r
e f f e c t
i s
i v e
c
c e p t .
b e ptance
４
／
９
o m e s
v a
l i d
hes
to
A
d u
t
y
t
o
r
ig
ht
t
o
r ed
q
e
l it
v e
r
the
v ed
r
h
e
g
query
引
４
／
1
5
B
m
a
y
d
u
t
y
o
t
r
i
g
h
t
(2)
t
o
r
e
q
A
h
a
s
a
渡
r
e
q
u
i
r
e
t
o
p
a
y
th
e
p
t
h
e
p
r
d u
t
y
t
o
す
A
Am a
ty
o
d
e
l
i
v
e
r
義
r
e
B
q
u
h
５
i
a
r
s
e
a
d
e
l
i
v
e
r
t
h
e
務
d
u
B
t
月
y
t o
t
h
e
g
o
o
d
s
が
t
p
o
a
y
p
1
a
0
t
y
h e
g
o
o
d
s
s
over
the
あ
p r
t
i
h
日
c
e
e
t o
o
the
first
る
p r
A
i
ま
c
b
e
y
５
／
１
r
Japanese
M a
b
y
y
で
1 0 .
iner
M a
に
y
Ship
1 a
0 s
t h a
.
A
h
query
d
u
t
y
t o
r
ig
h
t
o
p
d u
t
y
t
o t
５
／
５
t
h
e
p
r ir
c
t
h
e
p
(3)
d e l i v e
r
h e
g o o d s
w
the
h i c h
price
５
／
c o n f1
o0
r m s
t o
t h e
oods
is
c
o ／
n t3
r1
a
c t
５
ered
to
amines
６
／
５
goods
B
45
Contents







1. Introduction
2. Logical Jurisprudence
3. Basic legal sentence concepts and
structures
4. Case, query and solution
5. Logical structure of contract law regulating
changes in legal relations
6.Legal reasoning system on CISG, LES-5
7. Conclusion
46
6. Legal reasoning system on
the CISG, LES5






The clarification of logical structure of the contract law is applied
to construct a legal reasoning system on the CISG (LES5).
The relevant knowledge is written at first in the form of logical
flow chart and the represented in CPF in Knowledge Base.
The inference system and explanation system is written in logic
programming.
The system can deduce states of legal relationships at any time
point of cases as results of the application of the CISG to
concrete cases.
It can explain the reason of the deduction.
The systematization of law in LES5 might prove the legitimacy
and powerfulness of LJ.
47
Demonstration of LES-5
Switch to Netscape Navigator !
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
Contents







1. Introduction
2. Logical Jurisprudence
3. Basic legal sentence concepts and
structures
4. Case, query and solution
5. Logical structure of contract law regulating
changes in legal relations
6. Legal reasoning system on CISG, LES-5
7. Conclusion
92
yoshino:
7. Conclusion
On these way of formalization, the change
of legal relations is described as a change
A validity
Legal reasoning
system
(LES)
of  the
of legal object
sentences
get proposals
of the solutions
that describes
obligations.
will be useful for judges to
of cases and their
justification.

Legal reasoning system needs a good, general theory of Law. LJ
On the formalization, the fundamental legal
could afford the sound basis of LES.
meta rule sentence is confirmed under which

LJ
starts
fromrules
three
every
other
legal meta
areprimitives: legal sentences, the validity
and inference rules. It identifies the three sorts of legal
systematized.
sentences: rule and fact sentences, object and meta sentences,
complex
sentences.
Thus Ielementary
clarified theand
logical
structure
of
contract
can deductively

On law
thesystem
basiswhich
of these
conceptions, the basic structure of
prove legal
the change
of the legal
knowledge
has relation
been clarified.
along with the progress of events.

By taking up the CISG as an example, the structure of contract
law is thus clarified in terms of LJ.

The study results of knowledge clarification by LJ are put
into computer and a legal reasoning system on CISG, LES5 has
been developed.

As the basic deductive structure of law as a whole is
clarified and a LES on CISG is made on the basis, we could go
further to develop LES on various law fields and to integrate
93
them in the future.
I would conclude this lecture
with most important words:
 Thank
you!
94