A negotiation-based Multi-agent System for Supply Chain Management

Transcription

1 ngotiation-bad Multi-agnt Sytm for Supply Chain Managmnt Y Chn, Yun Png, Tim Finin, Yanni Labrou, Scott Cot Bill Chu, Jian Yao, Rongming Sun, Bob Wilhlm Computr Scinc and Elctronic Enginring Univrity of Maryland Baltimor County Baltimor, MD {ychn, ypng, finin, jklabrou, rcot1}@c.umbc.du Computr Scinc, Mchanical Enginring Univrity of North Carolina Charlott, NC {billchu, jyao, run, rgwilhl}@uncc.du BSTRCT Thi papr dcrib an ongoing ffort in dvloping a Multiagnt Sytm (MS) for upply chain managmnt. n our framwork, functional agnt can join in, tay, or lav th ytm. Th Supply Chain Managmnt Sytm (SCMS) functionality i implmntd through agnt-bad ngotiation. Whn an ordr arriv, a virtual upply chain may mrg from th ytm through automatd or mi-automatd ngotiation proc btwn functional agnt. W prnt our framwork and dcrib a numbr of ngotiation prformativ, which can b ud to contruct pair-wi and third party ngotiation protocol for functional agnt coopration. W alo xplain how to formally modl th ngotiation proc by uing Colord Ptri Nt (CPN) and w provid an xampl of tablihing a virtual chain by olving a ditributd contraint atifaction problm. Kyword Ngotiation, muliti-agnt ytm, upply chain managmnt ytm, ngotiation prforamtiv, Color Ptri Nt. 1. NTRODUCTON Computr oftwar and hardwar dvlopmnt lad to th apparanc of non-human oftwar agnci. oftwar agnt i conidrd a an ntity with goal, capabl of action ndowd with domain knowldg and ituatd in an nvironmnt [1]. Multi-agnt ytm (MS) ar uitabl for th domain that involv intraction btwn diffrnt popl or organization with diffrnt (poibly conflicting) goal and propritary information [1]. upply chain i a ntwork of upplir, factori, warhou, ditribution cntr and rtailr, through which raw matrial ar acquird, tranformd, producd and dlivrd to th cutomr [2]. upply chain managmnt ytm (SCMS) manag th coopration of th ytm componnt. n th computational world, rol of individual ntiti in a upply chain ar implmntd a ditinct agnt. Corrpondingly, a SCMS tranform to a MS, in which functional agnt cooprat with ach othr in ordr to implmnt ytm functionality. Mot of th prviou rarch work in thi fild t MS in a clod nvironmnt, that i, th ytm conit of a fixd numbr of ntiti/componnt and thy hav a common targt [2][3]. Th coordination of chain componnt i a hirarchical chduling problm [4]. Howvr, thi tting could not accuratly rflct th ral ituation in which a upply chain it. Firt, vry company in th upply chain ha it own intrt and goal vn though compani may alo hav intntion to dal with ach othr. Th xitnc of lf-intrt mak it difficult to modl th agnt coopration a a pur chduling problm. Scond, in a ral buin nvironmnt thr ar no obligation for compani to rmain with a upply chain for a crtain tim priod. Compani may join or lav th chain according to thir own judgmnt. n othr word, functional agnt hav to cooprat in a rlativly dynamic way. To addr thi problm, w propo a ngotiation-bad MS framwork for upply chain managmnt. n our framwork, thr i no prt rlationhip btwn functional agnt. Whn an ordr com, a virtual upply chain may mrg through ngotiation proc. Th componnt of th chain may chang according to th xtrnal ituation vn aftr th ordr ha bn accptd. Th papr i organizd a follow. Th propod framwork for ngotiation-bad MS i dcribd in Sction 2. Ngotiation prformativ for agnt ar givn in Sction 3. Sction 4 xplain how to u a CPN to formally modl th ngotiation proc. ral upply chain cnario i givn in Sction 5. Sction 6 prnt our concluion. 2. Framwork n thi ction w propo a framwork for th Multi-agnt Sytm (MS) for upply chain managmnt. Thi MS conit of htrognou typ of agnt, which implmnt om functionality of th upply chain managmnt, calld functional agnt. ll of thm hav om undrtanding of

2 ytm ontology and u a crtain gnt Communication Languag (CL) to mak convration. Th ytm ontology includ knowldg about th good that th ytm i daling with and intraction rul,.g. th ngotiation protocol ud in th ytm. Broadly, functional agnt can b dividd into two typ. On i ud for providing ytm information, calld nformation agnt, and may b intractd with th outid. Th othr typ of agnt i rlatd to a crtain good, for xampl, laptop and implmnt on pcial rol of th upply chain. nitially, functional agnt in th ytm might b unawar of who ar it cooprating parti in th chain. Thy can gt th information about potntial ngotiation partnr through th rlatd information agnt. Functional agnt could b autonomou agnt and mi-autonomou agnt. Thy could b a impl a CG-lik program and ditributd acro th ntrnt or othr larg-cal ntwork. Th knowldg of ach agnt rlatd to th good i modld a a t of contraint. Th intraction btwn thm, th ngotiation proc, i modld a a proc of collaborativly aigning valu to a t of variabl. For xampl, agnt may ngotiat th du dat and quantiti of ordr. Th dat and quantiti may b ubjct to th contraint of a producr' capacity. manufacturr may b willing to valuat diffrnt combination of ordr iz and du dat in ordr to find qualifid vndor with comptitiv pric offr. n th framwork, a numbr of information agnt ar prdfind, which ar in charg of providing diffrnt ytm information, for xampl, who want to ll or buy laptop. Excpt for th agnt, othr ytm componnt ar not fixd. Functional agnt may join th ytm and lav it according to thir own rul or ordr from thir ownr. functional agnt i aid to join th ytm if it advrti it abiliti and dird rol in a chain to on of th information agnt. Similarly, whn a function agnt want to lav, it ha to notify information agnt in which it rgitrd. Thr ar no cntralizd upr-agnt or ditributd mdiator [5] to handl th agnt coopration. ll th activiti occur through ngotiation proc, rgardl of whthr two id ar involvd in bargaining for om good intntionally or dcommitting a contract caud by th outid vnt. ytm i calld dad whn thr ar ithr no rgitrd agnt in all th information agnt or no virtual chain can b formd in a high prcntag whn cutomr ordr arriv (furthr dicuion on thi maurmnt i in progr). Thi framwork i ud to imulat th dynamic ituation that a SCMS ncountr, which rquir th managmnt ytm organiz th chain flxibly. t firt, th buyr agnt that carri th ordr from a cutomr look for a coopration partnr. ftr knowing who ar th potntial llr through th hlp of information agnt, th buyr agnt will ngotiat with th llr agnt dirctly and find th mot uitabl on for it own intrt. Convrly, th llr agnt may look for good manufacturr agnt by arching th information agnt (anothr olution i to lt th llr agnt pot th rquirmnt to th information agnt and wait for manufacturr to contact it). ll th mag will broadcat and gradually propagat through th whol ytm. Finally, a virtual upply chain may mrg, from matrial providr agnt to rtailr agnt. Th ngotiation proc rolv th incoming ordr contraint tp by tp acro th lf-intrtd agnt and during which a virtual chain mrg from th MS. Thi proc could b dcribd by th following figur: Figur 1 ngotiation-bad MS for upply chain managmnt (: functional agnt that act a a rol in upply chain; : information agnt) n th buin nvironmnt, th functionality of a SCMS ha bn dfind a th right product in th right quantiti (at th right plac) at th right momnt at minimal cot [6]. n our rarch, th functionality of a SCMS ha bn tranformd to contructing a virtual upply chain in a MS through th ngotiation proc among functional agnt, in which th contraint of an ordr ha bn fully or partial atifid. Th goal of th ongoing rarch ar to build up a MS ba on th framwork and upport a componnt-bad architctur whr diffrnt valuation tchniqu can b ud in conjunction with th ngotiation protocol dicud hr. On of th valuation tchniqu w ar xprimnting i bad on ditributd contraint atifaction [7]. W alo attmpt to xplor th analyi of th lif cycl of th ytm. 3. Ngotiation prformativ and protocol n agnt Communication Languag (CL) i a languag with prcily dfind yntax, mantic and pragmatic that i th bai of communication btwn indpndntly dignd and dvlopd oftwar agnt [8]. Functional agnt in a MS u a common CL to tranfr information, har knowldg and ngotiat with ach othr. Knowldg Qury and Manipulation Languag (KQML) and th CL dfind by Foundation for ntllignt Phyical gnt/ gnt Communication Languag ordr MS conitd of a batch of functional agnt rlatd to on kind of good Ngotiation outid information ordr

3 (FP CL) ar th mot widly ud and tudid CL. Each of thm offr a minimal t of prformativ to dcrib agnt action and allow ur to xtnd thm if th nw dfind on conform to th rul of CL yntax and mantic. n KQML thr ar no prdfind prformativ for agnt ngotiation action. n FP CL thr ar om prformativ, uch a propoal, and o on, for gnral agnt ngotiation proc, but thy ar not ufficint for our purpo. For xampl, thr ar no prformativ to handl third party ngotiation. n thi ction w prnt a ngotiation prformativ t dignd for MS daling with upply chain managmnt. 3.1 Critria for prformativ dfinition and lction Th critria w ud to dfin ngotiation prformativ ar th following: 1. Compatibl with xiting prformativ. From a practical prpctiv, to xtnd ithr KQML or FP CL prformativ t involv a imilar proc. Sinc in FPCL thr i a catgory containing four ngotiation prformativ [8], w choo to contruct th ngotiation prformativ t bad on thi ubt. 2. Dfining nw ngotiation prformativ bad on a ngotiation protocol. Thr i no clar man to judg th advantag and diadvantag of a particular xtnion of a tandard CL, jut a it i difficult to judg how to add nw word and phra to a languag ud by human bing. Som rarch attmpt to dfin a complt ngotiation prformativ t for an CL by numrating agnt bhavior that may occur in th ngotiation proc [9]. gnt action ar rlatd to pcific cnario o that it i hard to dcrib all typ of agnt bhavior without knowing th dtail of th ngotiation nvironmnt or tting. Thi mthod, actually, can only produc th incomplt ngotiation prformativ t imilar to th othr mthod. Conidring th ngotiation proc btwn functional agnt, many prformativ dfind in [9] ar unuabl. To lt functional agnt undrtand o many prformativ ound an ovrkill. ngotiation protocol i ud to organiz mag qunc among agnt. gnt ngotiation bhavior ar dpndd on th ngotiation protocol uing in th ngotiation proc. Sinc in a MS for upply chain managmnt, only limitd numbr of ngotiation protocol will b adoptd, it i appropriat to dfin ngotiation prformativ by dcribing agnt poibl rpon according to a pcific ngotiation protocol. n thi way it i air to vrify th ufficincy of th prformativ t through modling th protocol uing crtain formal tool uch a CPN. t th am tim, thi approach avoid th rdundant prformativ problm, and functional agnt nd only to larn a rlativly mall t prformativ for ngotiation. n th nxt two ction w dcrib th prformativ dignd for pair-wi and third party ngotiation protocol. 3.2 Ngotiation prformativ for pair-wi ngotiation protocol Prformativ for pair-wi ngotiation protocol ar ud whn two functional agnt ngotiat dirctly. Th prformativ dfinition conform to th FP CL pcification. W giv thir nam and corrponding maning in th following tabl: accptpropoal propoal trminat th action of accpting a prviouly ubmittd propoal to prform an action th action of calling for propoal to prform a givn action th action of ubmitting a propoal to prform a crtain action, givn crtain prcondition th action to finih th ngotiation proc Tabl 1 Pair-wi ngotiation prformativ nitially, on agnt tart ngotiation by nding a mag to th othr agnt. ftr vral round of convration in which propo and countr-propo ar xchangd, th ngotiation btwn two agnt will nd whn on id accpt (rjct) th othr id propoal or trminat th ngotiation proc without any furthr xplanation. t i not ncary that th functional agnt rpond to ach mag. functional agnt can imply ignor th incoming mag. t i th ndr rponibility to handl th lot mag or in ca of lack of rpon. Th pair-wi ngotiation protocol imulat a convration btwn two pron, in which on id nd an ak and th othr id nd a rply. Th diffrnc i in th pair-wi ngotiation protocol w hav to limit th rpon mag typ aftr a functional agnt rciv incoming mag o that th ngotiation proc do not bcom irrlvant to th topic, and at th am tim implify th mag handling proc. Tabl 2 giv a ummary about th poibl prformativ a functional agnt can u whn crtain prformativ com in: accpt-propoal Prformativ followd trminat NONE; propoal trminat NONE; propoal accpt-propoal rjct-propoal trminat NONE; rjct-propoal trminat trminat NONE; NONE.

4 Tabl 2 Pair-wi ngotiation prformativ and xpctd rpon 3.3 Ngotiation prformativ for third party ngotiation protocol (auction) Prformativ for a third party ngotiation protocol ar ud whn functional agnt ngotiat through th third party (auctionr). Som prformativ dfind for th pair-wi ngotiation protocol,.g. accpt-propoal, rjct-propoal, ar till ud for thi protocol. On nw prformativ, BD, i introuducd. Th yntax of BD i a follow: Bid: th action for a biddr to nd a corrponding rpon to an auctionr Bid :ndr <word> :rcivr <word> auctionr :contnt <xprion> pric for a good :languag <word> g., Knowldg ntrchang Format (KF) :ontology <word> ytm :in-rply-to <word> auction numbr :protocol <word> th dfault valu i Englih auction. n FP CL, NFORM i not includd in th catgory of a prformativ for ngotiation proc. n thi work, NFORM i tratd a a prfomativ aiding th ngotiation proc. Spcifically, NFORM i ud to tranfr mag btwn a llr agnt and an auctionr: th llr agnt NFORM th auctionr of what it want to ll and what kind of auction protocol it prfr; th auctionr NFORM th llr agnt of th auction rult. Th accpt-propoal (rjct-propoal) i ud by th auctionr to tll th biddr who ha won (lot). nitially, on functional agnt (llr) tart th ngotiation by nding an NFORM mag to th auctionr. Thi mag includ th good that it want to ll and th hight dird pric (or th contract that it want to b bought and th lowt dird pric) and th prfrrd auction protocol. ftr rciving th mag, th auctionr will broadcat it to potntial biddr (auming th auctionr know that information by qurying th information agnt) and organiz an auction according to th rquirmnt th llr ubmit. ftr vral round of convration, th ngotiation proc will nd with a dal that wa rachd btwn llr agnt and biddr. t i th auctionr rponibility to notify both th llr and biddr of th winnr and th lor. Th cnario i dcribd in th following figur: ccpt-propoal Biddr nform Bid Biddr Sllr uctionr Bid nform Rjct-propoal Biddr Figur 2 Third party ngotiation proc 4. Ngotiation proc modld by Colord Prit Nt (CPN) n thi ction w prnt th ngotiation proc in a impl MS aociatd with th ngotiation protocol and ngotiation prformativ that w hav propod. W u Colord Ptri Nt (CPN) a th modlling tool. CPN i dvlopd for ytm in which communication, ynchroniation and rourc haring play an important rol. t combin th trngth of ordinary Ptri nt with th trngth of a high-lvl programming languag. Ptri nt provid th primitiv for proc intraction, whil th programming languag provid th primitiv for th dfinition of data typ and th manipulation of data valu. Uually, a CPN modl conit of a t of modul (pag), which ach contain a ntwork of plac, tranition,arc and colord tokn. n a CPN-nt plac i ud to dcrib poibl tat of a proc. Th action of a proc ar dcribd by tranition. rc ar ud to connct plac and tranition. Thy ar indicatd by llip, rctangl and arrow lin in th diagram rpctivly. Tokn contain a dynamically aignd data. rc xprion dcrib th poibl data flow btwn a plac and a tranition. tokn i calld a colord tokn whn it i attachd a data valu. Th data valu may b of arbitrarily complx typ,.g., a rcord whr th firt fild i a ral, th cond a txt tring, whil th third i a lit of intgr pair. For a givn plac all tokn mut hav tokn color that blong to a pcifid typ. Thi typ i calld color. Th u of color t in CP-nt i totally analogou to th u of typ in programming languag. Color t dtrmin th poibl valu of tokn. Uually a languag calld CPN ML i ud to mak CP-nt dclaration. Th tatmnt writtn in CPN ML can b compild and ttd by om CPN tool, which giv ur convninc to judg th corrctn of th CPN diagram. Th modul intract with ach othr through a t of wll-dfind intrfac, imilar to many modrn programming languag. Th graphical rprntation mak it ay to th baic tructur of a complx CPN modl, i.., undrtanding how th individual proc intract with ach othr [10]. CPN diagram in figur 4 dcrib th pair-wi ngotiaion proc in a impl MS, which conit of two functional agnt bargaining for good. Th mag ud ar bad on th xtndd FP CL ngotiation prformativ t w propo. Color GENT = indx a with 1..2; Color PR = product GENT GENT; fun diff (x <> y); Color MES = ubt PR by diff dclar m; Color PERFORMTVE = accpt-propoal propoal rjctpropoal trminat; Color BRGN = String; Color CONTENT = product PERFORMTVE BRGN; Color E with ; fun = mult PR CONTENT(1`, GENT-1`, c); var,r : GENT;

5 GENT Waiting Rc. (r,,c) t M Snd E Timr r t (r,,c) Thinking MES nnacti MES Snt Snt GENT nactiv Rciv Snd Figur 3 Pair-wi ngotiation proc for a MS contitutd of two functional agnt Thinking From th diagram w can that thr ar thr diffrnt kind of plac: nactiv, Waiting, and Thinking, which rflct th tat an agnt might it in during a ngotiation proc. Both of th agnt in thi impl MS hav th am architctur. Th diffrnc btwn on functional agnt that ha thr plac and th othr that only hav two com from th rol thy play in th ngotiation proc. Th agnt that bgin th ngotiation, calld buyr agnt, which i hown on th lft id of th diagram, ha th rponibility of handling th lot mag or no rpon o it ha a xtra Waiting plac. Th llr agnt (th proc on th right) do not nd thi tat. Whn no mag com in, th llr agnt would imply rmain in th nactiv plac. n th diagram thr i on plac, Snt, and four tranition, Snd XX or Rciv XX, that rflct mag tat and tranaction. Th plac Snt i ud to dcrib th ituation that th mag i on th way from on agnt to th othr. Th four tranition ar ud to dcrib th action of agnt nding or rciving mag. Th CPN-ML dcription abov th diagram in figur 4 giv a formal way to xpr th ngation proc in th ytm. t can b ud for futur analyi. n th ytm, initially, both agnt ar in nactiv plac (tat). Whn th buyr id dcid to tart a ngotiation r r M(r,,c) r proc, it tak an action Snd Mag (), and it tat chang from nactiv to Waiting. Now th buyr i waiting for a rpon ( propoal, accpt-propoal, rjct-propoal or trminat). Whn th buyr id Rciv Mag, it tat chang from nactiv to Thinking. n thi tat th llr agnt nd to find out how to rply to th incoming mag. Of cour, it can jut ignor th mag. Eithr choic will cau it tat dirclty chang to nactiv. f thr i om rpon back to th buyr id, it tat will chang from Waiting to Thinking or nactiv. Othrwi, th Timr will nforc thi to happn (n th diagram w can th Timr iu a pcial non-colord tokn that control thi chang.).f th Thinking rult i nt out, all th traniton in th diagram would rpat again. Othrwi th buyr id will rturn to nactiv tat. Th ytm com back to th initial tat. Furthr dicuion and vrification rgarding th ngotation proc in thi ytm ar in progr. 5. Exampl n thi ction w prnt a concrt xampl of uing contraint to rprnt knowldg of functional agnt and how th contraint can b ud in valuating offr. Hr w do not prnt how to olv th ntir contraint problm for th ntir virtual upply chain mrgd, but intad w giv a dtaild xplaination of how to form on part of th chain, that i, from matrial upplir to manufacturr. W aum that all th compani ar rprntd a functional agnt and thy u pair-wi ngotiation protocol to intract with ach othr. Suppo company C ha a production chdul litd blow: T D T D whr T tand for tim priod and D tand for quantity du from th upplir. For ay of dicuion, w rtrict to only on part, X. Such a chdul i typically th output from company C' manufacturing rourc planning ytm gnt C tart with th contraint that it nd th quantiti at diffrnt tim priod. t may alo hav a databa of qualifid vndor, company and B, rprntd by agnt, and B rpctivly. gnt C nd a "call for propoal" () mag to both agnt and B. Upon th rqut of, agnt and B rpli with propoal in th form of contraint: Th upplir ' propoal may b: (if ((upply X) ( 2 upply_lad_tim 4)) ( (quantity 600) ( unit_pric X 3.05)))

6 (if ((upply X) ( 5 upply_lad_tim 10)) ((quantity 1500) (unit_pric X 3.00))) (if ((upply X) (upply_lad_tim 11)) (unit_pric X 2.95)) Th firt contraint man that if dlivry i xpctd within 2 to 4 wk, thn can only upply 600 pic of X at th unit cot of $3.05. Similarly, upplir B' contraint may b: (if ((upply B X) ( 2 upply_lad_tim 3)) 500) ( unit_pric X 2.95))) (if ((upply B X) ( 4 upply_lad_tim 8)) 1600) ( unit_pric X 2.90))) (if ((upply B X) (upply_lad_tim 9)) 2.85)) ( 2) ( 4) S1: q 600 p=$3.05 Supply lad tim ( 5) ( 10 ) S2: q 1500 p=$3. 00 X 11 S3: q 95 Product Typ upplir ( 2) ( 3) S4: q Figur 4 Sarch tr for contraint olving ( (quantity ( (quantity (unit_pric X Bad on all th contraint, agnt C will contruct a arch tr a follow. f a atifactory olution can b found, agnt C will accpt th on or both propoal from upplir or B. f no olution can b found, agnt C ha th following option: Chang it matr chdul. That i to ay, agnt C will try to rlax it own contraint, or Rqut upply and B to rlax on of thir contraint. Thi altrnativ would produc countr propoal mag to agnt or B. ftr vral round of ngotiation, gnt C might tup a coopration rlationhip with gnt or gnt B. B Supply lad tim ( 4) ( 8) S5: q S6: q Concluion n thi papr, w hav prntd a framwork of ngotiationbad MS for upply chain managmnt. Ngotiation prformativ for pair-wi and third party protocol hav bn dignd. CPN diagram xplaining ngotiation protocol mad up of th propod prformativ ha bn givn. Th dign and implmntation of th ngotiation-bad MS for upply chain managmnt i in progr. Th dfinition of ngotiation prformativ nd to b rfind and nw on will b addd in if ncary. Th ngotiation protocol xprd in CPN diagram will b givn a mor formal vrification. W modl th valuation proc a a ditributd contraint atifaction problm. Many challng rmain. Ky rarch iu includ: convrgnc bhavior of a ntwork of ngotiating agnt, tratgi, and ordr for dciding whn to rlax contraint. 7. REFERENCES [1] P. Ston and M. Vloo, Multiagnt Sytm: Survy from a Machin Larning Prpctiv, Undr rviw for journal publication, Fbruary, [2] M. Barbucanu, and M. S. Fox, Th nformation gnt: n nfratructur gnt Supporting Collaborativ Entrpri rchitctur, in Procding of Third Workhop on Enabling Tchnologi: nfratructur for Collaborativ Entrpri, Morgantown, Wt Virginia, EEE Computr Socity Pr, [3] N. Sadh, MSCOT: n gnt rchitctur for Multi- Lvl Mixd nitiativ Supply Chain Coordination, ntrnal Rport, ntllignt Coordination and Logitic Laboratory, Carngi Mllon Univrity, [4] D. Kjntad, Coordination Supply Chain Schduling, Ph. D. Dirtation, Dpartmnt of Production and Quality Enginring, Norwgian Univrity of Scinc and Tchnology, [5] R. Kalakota, J. Stallart, and. B. Whinton, mplmnting Ral tim Supply Chain Optimiaztion Sytm, in Procding of th Confrnc on Supply Chain Managmnt, HongKong, [6] NEVEM-workgroup, Prformanc ndicator in Logitic, FS Publication, Springr-Vrlag, [7] M. Yokoo, E. H. Durf, T. hida, and K. Kuwabara, Th Ditributd Contraint Satifaction Problm: Formalization and lgorithm, in EEE Tranaction on knowldg and data Enginring, Vol 10, No. 2, 1998, pp [8] FP '97 Spcification Part 2, gnt Communication Languag, 12.zip [9] B. Fordhan, K. Kalpaki, and Y. Yha, Extnding KQML for ntr-gnt Ngotiation, Matr Thi, Computr Scinc Dpartmnt, Univrity of Maryland Baltimor County, May, 25,1995.

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