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Mt s vn chn lc ca Cng ngh thng tin v truyn thng, Lt 2006

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TNG TC DA TRN ROLE TRONG HA AGENT

Trn nh QuKhoa Cng ngh Thng tin

Hc vin Cng ngh Bu chnh Vin thngEmail: [email protected]

Nguyn Th Thanh HuynTrng i hc Cng nghi hc Quc gia H Ni

Email: [email protected]

Tm tt:Cc mi trng tnh ton s hn thi thng l khng thunnht, ng vphn tn. Vic pht trin cc h phn mm phc tp trn mi trng nh vy i hiphi c cc phng php lun v cng c ph hp. Mc d phng php hng itng c s dng rng ri hin nay nhng n t ra khng thch ng vi yu cuthch nghi, phn tn v tng tc linh hot. Trong nhng nm gny, cch tip cnhng agent thu ht nhiu quan tm nghin cu v c cho l thch hp cho phttrin cc h phn mm phc tp. S thch ng ca h a agent vi mi trng tnh tonngy nay l do kh nng tng tc linh hot gia cc agent t ch khi thc hin mtcng vic vt qu kh nng ca mnh. Trong cc m hnh tng tc cho cc h a agent,m hnh tng tc da theo cu trc x hi vi role thu ht nhiu quan tm nghincu. Mc ch ca bi bo ny l nhm trnh by m hnh tng tc da trn khi nimrole vxem xt p dng m hnh ny cho thng lngsong phngtrong thng miin t.Tkho: H a agent, cng ngh phn mm hng agent, tng tc, role, thnglng.

1. GII THIUCc mi trng tnh ton hn thi nh mng truyn thng, mng Internet, web ng ngha

(semantic web), tnh ton hu khp (pervasive/ubiquitous computing)thng khng ng nht,phn tn, ng, m m chng ta khng th on trc cc hnh vi ca h thng trong thi gianthit k ([1], [2]). Vic pht trin cc h phn mmphc tp trn mi trng nh vy i hi phic phng php lun v cng c ph hp. Mc d phng php hng i tng c s dngrng ri hin nay l mt tin ho ng k trong lnh vc k ngh phn mm ca nhng nm 80 -90nhng n t ra khng thch ng vi yu cu thch nghi, phn tn v tng tc linh hot ([1]). Trongnhng nm gny, cch tip cn da trn agent cho pht trin cc h phn mm phc tp thuht nhiu quan tm nghin cu ([1-5]). Ngoi kh nng hng ch, phn x mt cch t ch vis thay i ca mi trng, cc thnh phn gi l agent cn c kh nng tng tc vi nhau hocdi dng cng tc, hp tc, cnh tranh, thng lng [5]. Tng tc trong h a agent cng ngycng c xem l mt vn quan trng cn phi i mt khi pht trin cc ng dng phn tn.
mailto:[email protected]:[email protected]:[email protected]:[email protected]

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Cho n nay c nhiu m hnh tng tc c ngh nh da trn ch hay da trnrole v m hnh da trn role1c xem l c nhiu u im trong pht trin phn mm ([3], [4]).Mc ch ca bi bo ny l nhm trnh by m hnh tng tc da trn role v nhng vn quan

tm nghin cu. Bi bo c cu trc nh sau: Phn 2 trnh by mt sc trng tng tc trongh hng i tng truyn thng; Phn 3 trnh by m hnh tng tc trong h a agent; Phn 4 lmt v d minh ho cho dng thng lng song phng da trn role v Phn 5 l kt lun.

2. TNG TC TRONG HHNG I TNG

Hin nay, cc phng php k ngh phn mm nh hng i tng, hng thnh phn hayhng agent u c xu hng phn r h thng mun pht trin thnh cc thnh phnnh hn.Mi thnh phnny s thc hin mt nhim v no v tng hp cng vic ca tt c cc thnh

phn ny s cho kt qu tng th cah thng. Nh vy, hai iu quan trng m chng ta cnphiquan tm khi xy dng h thng. Th nht, cch phn r cc thnh phn v cch thc hin cngvic ca cc thnh phnca h thng nh th no. Th hai, cc thnh phn phi hp vi nhautrong qu trnh thc hinmc tiu tng qut ca h thng bng cch no.

Mc ch ca chng ta trong bi bo ny tp trung xem xt vn th hai tc l cch m ccthnh phn cah thng thc hin c mc tiu tng qut. thc hin c nhim v chung,cc thnhphns phi tng tc ln nhau hoc theo kiuphi hp hnh ng hoc theo kiu cnhtranh nhm chia s ti nguyn nhthng tinT quan im cu trc x hi [3], tng tc trong hthng phn mm cng ging nh cc mi quan h x hi trong th gii con ngi, rt a dng v

phc tp. hiu r hn tng tc cn thit cho cc h thng phc tp, chng ta s phn tch ccc trng catng tc trong h hng i tng quen thuc.

2.1. Tng tc trong hhng i tngCc i tng trong h hng i tngl cc thnh phn tnh v tng tc gia chng ch

n gin l s trao i thng ip qua li gia cc bn. Thng ip c truyn bng cch gi thchin mt phng thc no i tng bn kia. i tng nhn s thc hin hnh ng tngng theo yu cu. Chng ta s d cm nhn c mi tng tc gia cc i tng l quan h mtchiu. i tng nhn thng ip ch vic thc hin yu cu v thng bo li kt qu (nu thnhcng) hoc li (khi khng thnh cng). Mt im na trong tng tc hng i tng l s kchhot ln nhau khng c s lan ta, tc l khi mti tng nhn c yu cu, n s thc hin yucu ny ch trong kh nng ca mnh m khng h c s lin h vi cc i tng khc tmkim thm thng tin cng nh nh s h trhay thng lng. Chnh im thiu lan to ny lmcho tng tc gia cc i tng km hiu qu. Chng ta s phn tch cn thn hn tng tc trongh hng i tng hiu c hn ch ca cch tip cn ny.

Trc ht, ta thy mc d i tng nggi trong n c trng thi v hnh vi nhng thccht n hon ton b ng, nghal n phi nhn c mt s kch hot no trc khi thc sthc hin mt hnh ng. Ni cch khc, i tng Obj1khng c c kh nng t thn kchhot hnh vica mnh m phi nh vo mt i tng khc. thc hn hnh vi ca mnh mti tng no khc Obj2s phi gi mt ligi thc thi mt phng thc cho Obj1 khi phngthc ny cho php truy cp kiupublic. Mt khi phng thc c gi, hnh ng tng ng s

1 tin li cho trnh by, trong bi bo ny, chng ti tm thi s dng thut ngrole v vai tr u c

ngha nh nhau.

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c thc hin. iu ny cng ng ngha vi vic, i tng khng c kh nng la chn hnhng m victhc hin hnh ng l do i tng khc p t ln.

Th hai, nh trnh by trn, i tng l hon ton b ng nn c th coi i tng ch

l nhng k bit nghe li i tng khc. Do vy, phng php hng i tng ch c th pdng cho cc ng dng trong mi trng m s cng tc c xc nh trcv d iu khin.N khng thch hp vi cc mi trng phc tp hoc c tnh cnh tranh cao. Hn ch ny chnh ldo quan im t tt c nhim v gi, v quyt nhthc hin cc hnh vi ln khch th cn chthkhng c vai tr g trong vic ny. Nhng nghin cuv t chc x hiv khoa hc chnh trcho thy cc phng php mt chiunh vy thng khng pht trin tt [2]. Cng vic s tinhnh tt hn khi cho nhngi tng thc hin hnh ng c mt ting ni no , tc l vicgi thc hin mt hnh ng tr thnh mt qu trnh tha thun gia cc i tng vi nhau. Nhvy, i tng thc hin hnh ng s hiu r hn v hnh ng m n cnphithc thi, t bitc l do m n c gi thc hin hnh ng c th trong tnh hung hin thi. Ch c nh vy,i tng thc hin mi c th t chi yu cu hoc t nht l ch ra nhng hu qu tim tng nun thc hin hnh ng theo yu cu y.Nhng nhn nh ny tr nn ng n hn khi phn

mm chuyn t hot ng trong mi trng chu s chi phi ca mt t chc n l ( hoc nhmcc t chc hp tc vi nhau) sang mi trng m m cc t chc phi cnh tranh vi nhau.Th ba, cc phng php hng i tng h tr rt t cho cu trc t chc nn tng ca

tng tc trong cc h thng phc tp. Cc mi quan h, tng tc trong h hng i tng chc nh ngha n gin bng cu trc lpk tha.

c im cui cng l phng php hng i tngkhng cung cp mt tp khi nim vcc k thut y m hnh ha cc kiu h thng khc nhau. i vi cc h thng phc tp,i tng, lp v module l nhng phng tin ct yu nhng cha tru tng ha. Cc itng ring l l mt tp hp cc phng thc v vic gi thc hin phng thc c cho lqu n gin nn khng thm t ht cc kiu tng tc xy ra trong h thng phc tp.

Vic nhn thc nhng nhc imca cc phng php hng i tng dn n spht trin nhng k thut tru tng ha mnh hn nh mu thit k, khung ng dngTrong khi

cha khng nh c tin b no th cc k thut ny gp phi nhiu tr ngi nhkhng thp ng c cc yu cu ca pht trin h thng phc tp.Phng php lun hng agent ccho l ng c vin nhm khc phc nhng hn ch ca phng php hng i tng cng nhcc mu thit k, khung ng dngnh cc c trng thng minh, t ch v di ng ca cac thnhphn agent. Phnn dnh trnh by m hnh tng tc ca cc agent.

3. M HNH TNG TC DA TRN ROLE TRONG HA AGENT

3.1 M hnh tng tc trong ha agent

Trong cc h thng a agent, nhim v chnh ca h thng c phn thnh cc nhim v nh hnv giao cho cc agent thc thi. Mi agent khi s m nhim mt nhim v con v n phi lmcch no hon thnh s mnh ca mnh. Cch thc m cc agent thc hin nhm t cmc tiu t ra l tng tc vi cc agent khc ly thng tin, cng tc, cnh tranh...Cng ngyngi ta cng nhn ra rng ngoi cc c trng t ch, phn x, th cc c trng tng tc mangtnh x hi cng tr thnh quan trng cho pht trin cc h phn mm phc tp. Trong h thng

phc tp nh tnh ton hu khp v dch v Web, cc tng tc c thc phn lm hai loi: Tng tc kiu cng tc, htr: y l nhng tng tc thng xy ra gia cc agent thuc

cng h thngnhng thuc cc h thng con khc nhau. Chng hn, mt agent bn cn bit

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thng tin vcc sn phm my tnh hin c, n s yu cu cho cc agent tm kim cungcp cc thng tin ny. Khi , quan h gia agent bn v agent tm kim l quan h cng tc.

Tng tc kiu cnh tranh:Thng thng, cc agent thuc cc h thng khc nhau c mitng tc mang tnh cnh tranh. Kiu tng tc ny xy ra khi cc agent mu thun li chvi nhau, tranh ginh nhau t c ci mnh mun, nh khi cng truy xut n cc tinguyn dng chung hoc quan h gia hai agent mua v agent bn.

Nh vy, khi pht trin mt h a agent, bn cnh nhng vn lin quan n tnh ton s hctrong bn thn cami agent, chng ta cnphi xem xt mt vn cng ht sc quan trng ltng tc gia chng. Hn na, cn phiphn tch rch ri hai kiu tng tc gip cho qutrnh pht trin h thng d dng hn.

Ngoi ra, i vi tng tc trong cc h thng phc tp nh tnh ton hu khp, dch vWeb cn t ra mt s yu cu phi chc nng trong vic pht trin ([1], [3]):

Tnh tng qut:Phng php pht trin ca chng ta phi tng i tng qut, ngha l mcd c lin quan n mt tnh hung c th nhng vn c th iu chnh c d dng v ctnh linh hot cao cho cc tnh hung khc.

Tnh cc b: Mt xu hng mi trong pht trin ha agent hin ny l vic chp nhn tnhcc b trong tng tc gia cc agent. Nghal agent c hiu l bao gmtp hp cc mitrng tng tc cc b trong tng tcxy ra. Da vo v tr hin thica mnh, mtagent c th c nh v trong mt mi trng tng tc cho trc v c quyn truy cpn ti nguyn cc b v tng tc vi cc agent thc thi trong cng mi trng.

Tnh dng li c: Nhng ngi pht trin khng nn t lm t u n cui mt ngdng bt k m nn s dng li nhng g ngi khc pht trin kh tt trc. Mt

phng php m hnhtng tc bt kphi cho php ngi pht trin s dng li d dngc m ngun v gii php ca ng dng.

Cc tnh nng hng agent: Yu cu quan trng nht l tng tc trong h a agent phic m hnh theo mt phng php hng agent no , ngha l tt c cc tnh cht ctrng ca agent phi c tnh n mt cch k lng.

Tnh thc tin: Bn cnh nhng phng php hnh thc m hnh tng tc nh ccphng php k ngh hng agent da trn UML, vic m hnh ha tng tc agent phic h tr v n gin ha theo mt cch thc c th.

C nhiu phng php khc nhau (xem [1], [4]) cho m hnh tng tc trong h a agent nhMessage passing, Linda.Phng php Message passing xem tng tc n gin ch l s traoi thng ip gia hai agent. Phng php Linda da ch yu trn m hnh cng tc khng cpi v khng gian d liu chia s. Nhn chung, cc phng php ny mi ch dng li mc thayi cc phng php tng tc trcy bng cch thm vo mt s khi nim mi nh meetingpoint, event channel hoc tuple space cho ph hp vi agent m cha thc s tnh n nhngc trng ca agent nh tnh x hi, kh nng phn ng v t ch. khc phc nhc im ny,ngi ta cng a ra mt vi phng php khc m hnh tng tcagent di dng cc dchv (service) v nhim v (task) nh Agentis. Tuy nhin, sghp ni ny khng a n mt cchtip cn tng qut v hn na, cha c mt phng php no h tr c cho cc phapht trin

phn mm. Mi phng php ch p dng chomt trong cc phaphn tch, thit k hoc ci t.iu ny li dn n smanh mn trong chnh gii php pht trinphn mm. Chnh cc hn chny dn n s pht trin m hnh tng tc da trn role v l mc ch ca phnc trnhby trong mc n.

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3.2 M hnh tng tc da trn roleKhi nim role c s dng rng ri trong cc phng php hng i tng trong

role c hiu l mt tp hnh vi m mt i tng c th p t ln i tng khc lm thay

i kh nng cng nh hnhvi ca i tng [2]. Mt s phng php khc th xemrole l mttp cc i tng hoc thc th nhn mnh s tng ng gia role trong chng trnh my tnhv trong th gii thc.

Bi bo ny theo quan im ca nhm Zambonelli et al. [2]: Role l tp cc kh nng,hnh vi mong iv tri thc m agent c thsdng n khi cn.Tp cc kh nng ca mt rolel tp cc hnh ngm mt agent m nhn role c th thc hin hon thnh nhim v camnh. Hnh vi c mong i l tp cc s kin m agent phi qun l nhm thc hin cnhim v ca role . Do , mt tng tc gia cc agent c th c biu din bi cp (hnhng, s kin). Phng php tng tc da trn role c mt s u im so vi cc phng phptrc nh sau:

Role cho php tch quan tm gia nhng vn v tnh tonv vn v tng tc trongqu trnh pht trin ng dng hng agent. Ccvn tnh ton c gi gn trong chnh

bn thn agent khi nh ngha hnh vi c bnca n. Mt khc, giao tip ca agent vi ccagent khc s c tch hp trong role v cc hnh vi thm khc. Ngi ta c th pht trinagent v role c lp nhau v mt thi gian cng nh phng php. iu ny gip tngkh nng phn r v do lm n gin ha qu trnh pht trin h thng.

Role l mt khi nim tru tngmc cao nn cho php s c lp nht nh gia cctnh hung c th, nh nng cao c tnh tng qut ca cc phng php da trn role.

Role c th c pht trin theo nhu cu v quy tc cc b. Nhvy m tnh cc b cnng cao trong khi pht trin cc h thng phn tn c quy m ln.

Role cho php s dng li gii php cng nh sn phm phn mm. Trn thc t, rolethng gn lin vi mt ng cnh h thng v c lp vi agent. V th, ngi thit k cth s dng li nhng role c thc hin tt trc cho nhng ng dng tng t.Chng ta hon ton c th coi role l mt dng ca mu thit k (design pattern) v khi tp cc role c lin quan cng vi nh ngha cch thc chng tng tc vi nhau c coil mt gii php cho mt vn c th v n c th c s dng li trong nhiu tnhhung tng t.

Hai yu cu khc l tnhagent v kh nng s dng c th khng suy ra c trc tip t rolenhng tng phng php c th s c cch p ng nhng yu cu ny. C nhiu m hnhtng tc da trn role v mt stiu chun c a ra nh gi, so snh (xem [1]) cc mhnh ny nh: n c h tr nhiu pha trong qu trnh pht trin hay khng? N c cung cp tp khiu m t role v cc hnh vi ca agent hay khng? C p ng c s thay i mi trngthc thi hay khng? Ngi pht trin c th dng bn phn tch da trn role ca phng php ny thit k, ci t bng phng php khc hay khng? Da trn nhng tiu chun ny m ngi taa ra mt s nhn xt cho mt s phng php lun khc nhau sau y ([1], [5]):

AALADIN: Mtphng php da trn bakhi nim c bn l agent, role v group, trong group l mt tp cc agent c coi l thnh phn thc hin nhim v nh nht. Tc ln l mc thp nht c th hon thnh c mt nhim v ca h thng. Tuy nhin, trong

phng php ny role gn cht vi khi nim agent nn n s gy kh khn cho nhngngi lp trnh mun c c s c lp gia role v agent.

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3.3.1.M hnh tng tcTrong m hnh BRAIN, role c nh ngha l mt tp cc kh nng v mt hnh vi mong i .Tp cc kh nng l tp cc hnh ng m mt agent m nhn mt role c th thc hin honthnh nhim v ca n. Mt hnh vi mong i l tp cc s kin m agent phi qun l c thhnh x c nh ngi dng yu cu.Tng tc gia cc agent c biu din bi mt cp (hnh ng, s kin). Cp (hnh ng, skin) ny c h tng tc mc di x l. Hnh 2 minh ha cch thc tng tc gia haiagent. Khi agent A mun tng tc vi agent B, n s phi thc hin mt hnh ng (hnh ngny c chn trong s cc kh nng c cung cp bi role m n m nhn). Hnh ng ny sc dch thnh mt s kin nh h thng tng tc mc di. S kin s c gi ti agent B, y B s c nhim v qun l s kin nymt cch hp l.

M hnh ny l tng qut, n gin vph hp vi cc c trng ca agent: Cc hnh ng c th

c coi l mt th hin c th ca tnh t ch ca agent trong khi cc s kin phn nh tnh phnng ca agent.3.3.2. Tp k hiuTp k hiu c xut trong m hnh BRAIN l XRole. Tp k hiu ny cho php chng ta nhngha role di dng XML. Vic s dng XML em li tnh lin tc cao bi n cho php cc itng phn mm khc nhau, c pht trin bi cc cng ngh khc nhau c th dch v hiuchnh xc cc nh ngha role. Hn na, nhc XML, nhng ngi pht trin phn mm c th cnhiu cch nhn khc nhau v cng mt ti liu.iu ny gip chng ta la chn dng ch nhngthng tin tht cn thit. Mt im cn lu na l do c nhiu cch khc nhau nhn nhn mtti liu nn cc pha khc nhau ca quy trnh pht trin phn mm c th dng cng mt thng tin,to ra s lin tc trong sut qu trnh pht trin. V d, trong pha phn tch, phn tch vin to ra tiliu Xrole theo lc XML c trong tp k t Xrole ca BRAIN. Chnh ti liu ny s ch ra

mt s tnh nng ca role phi nh ngha sau ny. Sau , nhng ti liu ny s c dch thnhcc ti liu nh dng HTML cung cp bn m t mc cao tin cho vic s dng cc phasau.

Trong pha thit k, cc ti liuXrole ny c dch thnh cc ti liu HTML chi tit hn gi ranhng chc nng ca cc i tng lin quan. Cui cng, ti pha ci t, mt ln na chnh cc tiliu Xrole ny s c trin khai thnh cc lp Java thc thi cc thuc tnh c role.

Role

A

Khnng

Role B

KhnngH thngtng tc

Hnh ng

S kin

Hnh 2. Tng tc gia hai agent trong thng lng

Hnh vi Hnh vi

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3.2.3. C stng tc BRAINNh trong hnh v pha trn ch ra, BRAIN cho php cc bn ci t khc nhau ca c stng

tc c th c gn vo h thng agent mt cch d dng thng qua h qun tr platform. C stng tc cho php cc agent m nhn role theo nhiu cch khc nhau. Ngoi ra, c stng tccng qun l cc tng tc gia cc agent vi nhau theo cch n s thc hin vic dch mt hnhng thnh mt s kin v chuyn s kin ny ti agent nhn. C stng tc c th iu khintngtc v thit t cc chnh sch cc b, nh cho php hay t chi tng tc gia agent mnhn mt role no ...Tnh nng ny ca BRAIN to ra tnh thch nghi cao bi mi nn c th sdng mt nn tng tc hiu qu nht vi mc ch ca n . Trn thc t, khng c mt bn ci tno l tt nht, vic s dng kin trc nh vy cho php chng ta pht trin nhiu bn ci t khcnhau, kim th chng tm ra ci ph hp nht vi mc ch s dng c th. Chng ta cng cn phi lu rng c s tng tc l tng thp nht trong khung BRAIN (xemhnh 1) v iu ny c ngha l hai tng trn s khng b thay i theo cc c s tng tc. Khnng ny cho php chng ta s dng li cc phn mm v tt c cc ti liu phn tch v Xrole c

th c s dng trong khi ci t c s tng tc. Ni cch khc, vic s dng mt kin trc 3tng nh vy cho php ngi pht trin tp trung vo pha phn tch m c th b qua cc chi tit vc s tng tc. iu ny thc s c ngha bi hai agent hai nn vi ci t BRAIN khc nhauvn c th tng tc bng cch trao i s kin vi nhau. Hin nay nhm tc gi ca BRAIN a ra hai bn ci t khung ny l RoleSystem v RoleX.Trong bi ny, chng ti ch xem xtbn ci t RoleSystem.Bn ci t RoleSystem biu din role bng cc lp tru tng . Trong h thng ny, mt agentmun m nhn mt role, n phi ng k vi nhn h thng. Khi RoleSystem nhn c yu cung k, n phi kim tra xem agent c kh nng m nhn role yu cu hay khng. Nu c, ngi li cho agent mt th xc nhn ng k. Th ny cho php agent m nhn role m n yu cu,tc l c th thc hin c cc hnh ng c trong role . Thc t, agent thc hin hnh ng vch s kin t agent khc u thng qua th ng k ca n. Vy nn c th coi th ny l cu ni

gia agent v role.Khi agent mun gii phng role, agent ch cn giao tip vi nhn RoleSystem thi hi role. Lih thng s v hiu ha th ng k ca agent n khng s dng th ny c na, ng nghavi vic thot khi mi trng tng tc.Bn ci t ny c u im l s dng v ci t kh n gin .

4. C TTHNG LNG SONG PHNG DA TRN ROLEThng lng l mt khi nim thng c dng ch tin trnh tha hip gia cc bn (c lich xung t nhau) i n mt tho thun thng nht c th chp nhn c. Trong thng miin t ([6], [7]):

Thng lng tng l mt qu trnh thng lng, trong , ngi mua v ngi bn c thay th

bng cc agent. Vic tm kim, mua bn v tho thun gia ngi mua v ngi bn c thc hin tng bi cc agent.

C nhiu kiuthng lng t ng khc nhau [7]: Thng lngkiu u gi, u thu, ch ldng thng lng trong mi phin giao dch c th c mt agent bn, nhiu agent mua (u gi),nhiu agent bn mt ngi mua (u thu) hay nhiu ngi bn v nhiu ngi mua (ch). Loithng lng ny lin quan nhiu n thuc tnh gi c ca hng ha.Thng lng song phng

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l dng thng lng ch c mt bn mua v mt bn bn tham gia vo qu trnh giao dch.Thng lng c thlin quan n nhiu thuc tnh ca hng ha nh gi bn, cht lngPhnny ch tp trung vo xem xt c t thng lng song phng theo m hnh role.

4.1. Thng lng song phng da trn rng buc mTheo m hnh thng lng da trn rng buc mc trng s ca Jennings [7], yu cu ca bnmua c din t bng cc rng buc mi vi sn phm thng qua thuc tnh nhthch, rtthch... Vic nh gi sn phm mbn bn a ra c tha mn yu cu hay khng cng khngtht s chc chn m phi do bn mua quyt nh. V vy, cn c vo u tin ca cc thuc tnh,

bn mua cung cp cho bn bn cc rng buc ca mnh ln sn phm ln lt theo th t u tin tcao xung thp.

i vi bn bn, hs tm kim cc sn phm tha mn cc rng buc theo th t gim dn u tin. Gi s, ngi mua cn mua mt chic my tnh xch tay, nu bn mua cn nht l my

phi r, sau l cu hnh cao th bn bn s u tin tm sn phm tha mn v gi c trc,trong s sn phm tm c s tm nhng ci tha mn rng buc v cu hnh...Trong qu trnh tmkim, nu khng tm thy sn phm tha mn cc rng buc, bn bn s yu cu bn mua nhng

b bt cc rng buc. Tuy nhin, vic nhng b khng th l v hn v qu trnh thng lng skt thc khi tm c sn phm tha mn rng buc ca bn mua hoc bn mua khng th nhng

b hn c na (chi tit tham kho [8], [9]).

4.2. M hnh thng lng song phng da theo roleChng ta xt mt trng hp c th l mt h thng mua bn my tnh nhm minh ha cch thchot ng ca cc h a agent da trn role. H thng ny s phi thc hin cc cng vic nh sau:

Ly thng tin yu cu t ngi mua: gi c sn phm, nh sn xut, mu sc, cu hnh... Tm kim cc nh cung cp sn phm. Thng lng mua c sn phm nh .

Nh vy, cc agent i din ngi mua s phi tng tc vi cc agent ca nhiu h thng khc trong cc mi trng khc nhau. Cc chc nng ca h thng bao gm cc role sau:

Request_Getter (Ly thng tin), Buyer (Bn mua) v Seller (Bn bn).Vai tr Request_GetterRole ny chu trch nhim ly cc yu cu t ngi dng. Mi ngi dng khi c nhu cu mua mtmt hng no s phi khi ng mt agent ngi dng. Sau agent ny s tm kim v mnhnmt role gi l Request_Getter. Khi m nhn role ny, agent s yu cu ngi dng nhpvo cc yu cu v sn phm cn mua. Vic ly yu cu ny s c thc hin thng qua role bngcch gi mt dch v trong role, v d Get_Request . Sau khi ly c yu cu ngi dng, agent s

phi lu cc yu cu ny di dng sao cho d hiu v chuyn c d dng sang h thng khc.V vy, role Request_Getter phi c thit k c mt nh dng lu tr thng tin tt v mt

phng thc tr d liu v cho agent. nh dng tt nht thng c dng biu din d liuhin nay l XML do tnh kh chuyn v gn nh ca n. gii quyt vn th hai l tr d liuv cho agent, agent s phi gi mt phng thc, chng hn, store_data ly d liu v lu vomt bin trong. Sau khi lu li d liu trong agent, agent ngi dng s gii phng roleRequest_Getter v bt u qu trnh i tm cc h thng thng mi in t.

Vai tr Buyer, Seller v qu trnh thng lng

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Agent ngi s dngs tm kim ngi bn, ng k v m nhn role ngi mua Buyer. Vi vicm nhn vai tr Buyer, n c php giao dch vi agent bn ca h thng. Agent bn s lunm nhn vai tr Seller trong h thng.

Vai tr Buyer c cc hnh ng v s kin sau: Hnh ng: send_request (gi yu cu n agent bn), make_order (t hng), refuse (t chi sn

phm agent bn a ra), end (kt thc thng lng). S kin: list_sent (danh sch c gi), downrequirement (bn bn gi gim bt yu cu).

Vai tr Seller c cc hnh ng v skin sau: Hnh ng: get_request (ly yu cu), require_search (yu cu tm kim thng tin), list_product

(lit k danh sch sn phm t yu cu), send_list (gi danh sch sn phm n agent mua),suggest_downRequirement ( ngh gim bt yu cu)

S kin: request_sent (yu cu c gi), refused (bn mua t chi ngh), end (kt thc thnglng)

Thng lng gia hai agent ny s tin hnh theo cch thc sau: Agent mua, qua vai tr Buyer s gi cho vai tr Seller ca agent bn cc thng tin v yu cu ca

ngi dng. Agent bn s phn tch yu cu v kim tra xem n c hng ha tha mn yu cu khng. Qu trnh

tm kim sn phm p ng s khng c trnh by y. Nu agent bn tm ra mt danh sch cc sn phm tha mn hon ton yu cu v gi cho agent

mua th da trn quyt nh ca mnh Agent mua s tin hnh t.Qu trnh thng lng kt thcti y.

Nu agent bn khng tm ra sn phm p ng mi yu cu ca agent mua. N a ra danh schp ng nhiu yu cu nht v ngh agent mua gimbt yu cu cha tha mn. Nu agent muachp nhn, qu trnh thng lng tip tc, ngc li agent mua s kt thc thng lng vchuyn qua h thng khc.

5. KT LUN

Bi bo ny trnh by nghatng tc gia cc thnh phn trong h thng t quan im hngi tng v hng agent. Da trn cc phn tch, chng ti xem xt m hnh tng tc ca ccagent da trn role. M hnh ha agent da trn tchc x hi vi role ang l ch thu htnhiu quan tm nghin cu. Chng ti cng ara v d s dng m hnh da trn role ct dngthng lng song phng trong thng mi in t. Nhng trnh by trong bi bo nymi ch l nhng bcu nghin cu ca chng ti. Nhiu vn cn phi tip tc nghin cuhn na nh lm th no qun l cc role, ci t h thng da trn role, m hnh hnh thc khinim role... l nhng ch nghin cu tip theo v sc trnh by trong cc cng trnh khcca chng ti.

TA LIU THAM KHO

[1] G. Cabri, L. Ferrari and L. Leonardi, Agent role-based collaboration and coordination: asurvey about existing approaches, The 2004 IEEE Systems, Man and CyberneticsConference, Netherlands, October 2004.

[2] G. Cabri, L. Ferrari, L. Leonardi, F. Zambonelli, Role-based Approaches for EngineeringInteractions in Large-scale Multi-Agent Systems

[3] G. Cabri, L. Ferrari, L. Leonardi, F. Zambonelli, Implementing Role-based Interaction forInternet Agents, International Symposium on applications and Internet, USA, 2003.

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[4] G. Cabri, L. Ferrari, L. Leonardi, F. Zambonelli, BRAIN: a framework for flexible role-based interacions in multiagent systems , Workshop of EUMAS, UK, 2003

[5] N. R.Jennings, M. Wooldridge, F. Zambonelli Developing Multiagent Systems: the GaiaMethodology, ACM Transactions on Software Engineering and Methodology, Vol. 12,No.3, 2003, pp. 317370.

[6] M. He, N.R. Jennings and H. Liung. On Agent - Mediated Electronic Commerce, IEEETransactions on Knowledge and Data Systems, 15(4), pp.985-1003, 2003.

[7] X. Luo, N. R. Jennings et al. A Fuzzy Constraint Based Model for Bilateral, Multi-issueNegotiations in Semi-competitive Environments, Journal of Artificial Intelligence, V.148,No.1-2, pp.53 -102, Aug. 2003.

[8] T.D. Que and N.M. Hung. Agent making decision based user preferences, Proceedings ofthe National Conference on Information Technology, Thainguyen, Vietnam, August 2003,

pp.15-27.

[9] T.D. Que and N.M Hung. Bilateral negotiation among agents in e-commerce, Proceedingsof Scientific Conference of Posts and Telecommunication, Hanoi, Vietnam, Aug. 2003,

pp.48-55.

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