Flexible Deadlines o Di ec ed Obliga ions in Agen -based
Business Con ac s
(Ex ended Abs ac )
Hen ique Lopes Ca doso ∗
LIACC, DEI / Faculdade de Engenha ia,
Uni e sidade do Po o
R. D . Robe o F ias, 4200-465 Po o, Po ugal
hlc@ e.up.p
Eugénio Oli ei a
LIACC, DEI / Faculdade de Engenha ia,
Uni e sidade do Po o
R. D . Robe o F ias, 4200-465 Po o, Po ugal
eco@ e.up.p
ABSTRACT
In B2B con ac enac men , coope a ion should be aken
in o accoun when modeling con ac ual commi men s h ough
obliga ions. We ad oca e a di ec ed deadline obliga ion ap-
p oach, aking inspi a ion on in e na ional legisla ion o e
ade p ocedu es. Ou p oposal is based on au ho iza ions
g an ed in speci ic s a es o an obliga ion li ecycle model.
Flexible deadlines p o ide an addi ional le el o coope a ion
be ween con ac ual agen s. Mo eo e , agen s inc ease hei
decision-making op ions conce ning obliga ions.
Ca ego ies and Subjec Desc ip o s
I.2.11 [Dis ibu ed A i icial In elligence]: Mul iagen
sys ems
Keywo ds
No ms, No ma i e Beha io , Con ac , Deadline
1. INTRODUCTION
In coope a i e Vi ual O ganiza ions, agen s (en e p ise
delega es) sha e hei compe ences in a egula ed way, h ough
commi men s exp essed as no ms in con ac s. The impo -
ance o pu suing a common goal demands o lexibili y o
ope a ions: agen s should acili a e compliance o hei pa -
ne s, because g oup success also bene i s each agen ’s p i a e
goals, which a e no limi ed o he business in p og ess, bu
also conce n u u e oppo uni ies ha may a ise.
Many app oaches o no ma i e mul i-agen sys ems a e
abs ac ed away om hei po en ial applica ion domain,
and gi e deon ic ope a o s an uni e sal seman ics (e.g. dead-
line obliga ions a e iola ed i he obliged ac does no hap-
pen be o e he deadline). We a gue ha in some domains –
such as business con ac s – his app oach is no desi able.
Fo ins ance, he UN Con en ion on Con ac s o he In e -
na ional Sale o Goods (CISG) [4] es ablishes wha pa ies
∗Suppo ed by FCT unde g an SFRH/BD/29773/2006.
Figu e 1: Di ec ed oblig. wi h li eline and deadline.
may do in case o deadline iola ions. In some cases, obliga-
ions may be ul illed a e he deadline (A icle 48), which
may hemsel es be ex ended (A icles 47 and 63), deno ing
a lexible and e en coope a i e ace o ade con ac s.
We p opose a di e en app oach o model obliga ions in
MAS o he business con ac s domain. Following a coop-
e a i e business pe o mance pos u e, we a gue ha obliga-
ions should be di ec ed, and ha deadlines should be lex-
ible. In ou model, au ho iza ions a e g an ed on speci ic
s a es o a li ecycle o ime- amed di ec ed obliga ions.
2. DIRECTED DEADLINE OBLIGATIONS
Deon ic ope a o s (such as obliga ions) can be modeled
wi h di e en ea u es. Ou p oposal o handling con ac-
ual obliga ions combines deadline [1] and di ec ed [3] obli-
ga ions. We also cope wi h he ac ha an icipa ed ul ill-
men s a e no always welcome (in CISG’s A icle 52, his is
he case when s o age cos s a e ele an ). An obliged ac
should he e o e be ob ained wi hin a ime window, delim-
i ed by a li eline and a deadline. A no m s→Ob,c( , l, d)
indica es ha i s hen b(bea e ) is obliged owa ds c(coun-
e pa y) o b ing abou ( ac ) be ween l(li eline) and d
(deadline). I bdoes no b ing abou be ween land d,
hen cis au ho ized o eac agains b(see igu e 1, whe e
he shaded a ea indica es he pe iod o ime wi hin which
he achie emen o will ce ainly ul ill he obliga ion).
2.1 Tempo al Viola ions
Figu e 2 con ains he s a e ansi ion diag am o di ec ed
obliga ions wi h li elines and deadlines. The obliga ion is
ac i e (Ob,c( , l, d)) when p esc ibed by a no m (whose si -
ua ion si became ue). When la ises, i becomes pending,
unless an an icipa ed achie emen o occu s; in his case
he e is a li eline iola ion (LViolb,c). I he deadline oc-
cu s be o e , he e is a deadline iola ion (DViolb,c). I
occu s while he obliga ion i sel is no ye in a iola-
Figu e 2: Li ecycle o a di ec ed obliga ion wi h li e-
line and deadline.
ion s a e (Violb,c), he obliga ion is ul illed (Ful b,c). The
coun e pa y’s eac ion o a deadline iola ion will change
he obliga ion’s s a e i he agen chooses o deem he obli-
ga ion as iola ed, by denouncing his si ua ion: Denc,bis
a denounce om c ega ding he ailu e o b o comply wi h
his obliga ion. Once he ac being obliged is b ough abou ,
he obliga ion canno be iola ed. In case o an an icipa ed
achie emen o , we only need l o conside he obliga ion
as ul illed. This does no , howe e , p e en he coun e -
pa y om eac ing o his ea ly ul illmen in o he less
s ic ways (which can be cap u ed by app op ia e no ms
whose si ua ion is based on LViolb,cand o he ac s).
Using empo al logic (namely i s be o e ope a o B), he
ollowing ela ions exp ess he seman ics o ou obliga ions:
•Ob,c( ,l,d)∧( B l)|=LViolb,c( ,l,d)
•Ob,c( ,l,d)∧l∧( B d)|=Ful b,c( ,l,d)
•Ob,c( ,l,d)∧(d B )|=DViolb,c( ,l,d)
•DViolb,c( ,l,d)∧( B Denc,b( ,l,d)) |=Ful b,c( ,l,d)
•DViolb,c( ,l,d)∧(Denc,b( ,l,d)B )|=Violb,c( ,l,d)
Bela ed ul illmen s a e allowed be o e denounces, acco d-
ing o he ou h ela ion abo e.
2.2 Implemen a ion wi h Rules
I we wan o de elop app op ia e ools o moni o con-
ac s a un- ime, we need o g ound his seman ics in o a
easoning engine capable o esponding o e en s in a imely
ashion. Using a ule-based in e ence engine, we de ine he
ollowing ( o wa d-chaining) ules:
•Ob,c( ,l,d)∧ ∧ ¬l→LViolb,c( ,l,d)
•Ob,c( ,l,d)∧l∧ ∧ ¬d→Ful b,c( ,l,d)
•Ob,c( ,l,d)∧d∧ ¬ →DViolb,c( ,l,d)
•DViolb,c( ,l,d)∧ ∧ ¬Denc,b( ,l,d)→Ful b,c( ,l,d)
•DViolb,c( ,l,d)∧Denc,b( ,l,d)∧ ¬ →Violb,c( ,l,d)
Each ela ion o he o m (e1B e2) is ansla ed in o a
conjunc ion e1∧ ¬e2. This allows us o de ec he momen
a which he be o e ela ion holds, and consequen ly o ea-
son abou i s consequences. Rela i e deadlines (common in
business con ac s) equi e imes amping e en s, which al-
lows o a e inemen on he implemen a ion o hese ules
(no shown o space es ic ions).
3. DECISION-MAKING
The au ho iza ion app oach desc ibed abo e en iches he
decision-making space. Besides hei own commi men s,
coun e pa ies may decide o e di ec ed obliga ions a e
deadlines (a iola ion s a e is de e mined by his choice o
denounce). In a con ac , bo h pa ies bea obliga ions o
ob ain ce ain ac s, which bene i coun e pa ies. A con-
ac con ains u he no ms dependen on he ul illmen o
iola ion o p e ious obliga ions. In o de o model he deci-
sion making p ocess, we need o assess an agen ’s alua ions
on he obliga ion s a es and ac s he is able o b ing abou .
Le a( ) and a(S) deno e he alua ion agen amakes o
ac o s a e S, espec i ely (as in [2], whe e hese a e
used o check co ec ness o con ac s, while we ocus on he
cou se o con ac execu ion). When alua ing ul illmen
o iola ion s a es, agen s should ake in o accoun wha
u he commi men s hose s a es igge . Focusing on he
coun e pa y, o an obliga ion Ob,c( , d) we ha e:
c(Ob,c( , d)) >0 obl. is asse o coun e pa y
c( )> c(Ob,c( , d)) cbene i s om
c(Ful b,c( ,d)) ≤0cmay acqui e obligs. a e
c(Violb,c( ,d)) ≥0cmay be compensa ed a e
We may now say ha cshould denounce (and hus ob ain
he iola ion) i c( ) + c(Ful b,c( ,d)) < c(Violb,c( ,d)).
We conside ha alua ions may a y wi h ime (i makes
sense o hink o c( ) as possibly dec easing wi h ime).
E en when he abo e condi ion does no hold, cmay s ill
op o ole a ing he less p e e ed si ua ion o ailu e o
ma e s o con lic ing goals. On he o he hand, in en i on-
men s en iched wi h social ea u es agen s can exploi , hey
can decide o beha e coope a i ely e en when hey ha e o
bea a con ained disad an age – mo e han being al uis ic,
agen s may y o enhance hei us awa eness in he com-
muni y, om which hey will bene i in u u e in e ac ions.
4. SUMMARY
Mos implemen a ions o no ms in MAS igno e he need
o ha ing di ec ed obliga ions om bea e s o coun e pa -
ies. This is because in hose app oaches obliga ions a e seen
as (implici ly) di ec ed om an agen o he no ma i e sys-
em i sel . I is up o he sys em o de ec iola ions and o
en o ce he no ms which a e embedded in he en i onmen .
On he con a y, con ac ual obliga ions a e nego ia ed in o
con ac s and di ec ed o speci ic con ac ual pa ne s.
We s a ed om p e ious heo e ical app oaches o model
au ho iza ions, and de eloped a mo e conc e e o maliza ion
by linking au ho iza ions wi h a lexible model o deadlines.
Obliga ion iola ions a e now dependen on he coun e -
pa y will o claim hem. Agen decision-making is en iched
in ou model, because bo h pa ies in ol ed in di ec ed obli-
ga ions may ha e a say ega ding hei iola ion. When
conside ing such obliga ions as in e linked h ough no ms in
a con ac , agen s should e alua e he consequences o ul ill-
men and iola ion s a es as s a ed in he con ac . Fu he -
mo e, in “socially ich” en i onmen s, agen s should explo e
he alue o u u e ela ionships by enhancing hei pe cei ed
us wo hiness and p edisposi ion o acili a e compliance.
5. REFERENCES
[1] J. B oe sen, F. Dignum, V. Dignum, and J.-J. Meye .
Designing a deon ic logic o deadlines. In DEON 2004.
[2] N. Desai, N. C. Na end a, and M. P. Singh. Checking
co ec ness o business con ac s ia commi men s. In
AAMAS 2008.
[3] Y.-H. Tan and W. Thoen. Modeling di ec ed obliga ions
and pe missions in ade con ac s. In HICSS 1998.
[4] UNCITRAL. Uni ed na ions con en ion on con ac s
o he in e na ional sale o goods (cisg), 1980.