Luan Van Multi Agent

8/2/2019 Luan Van Multi Agent

1/192

LI GII THIU

Trong nhng nm gn y, s pht trin mnh m ca cc cng ngh truyn thng v

internet nh hng su rng n mi mt ca cuc sng t kinh t, khoa hc nvn ho v x hi. R rng s pht trin ca phn cng ng vai tr rt quan trng

trong qu trnh tin ho ny nhng yu t then cht nh hng mnh m n x hi

tri thc ngy nay chnh l bn thn phn mm. Khi m mng my tnh v Internet tr

thnh ph bin th vic x l thng tin phn tn, chia x v tch hp thng tin thng

qua ng truyn gia cc my vi nhng c s d liu c nhng khun dng khc

nhau cng ngy cng tr nn ph bin. iu ny dn n mt thch thc mi i vi

gii pht trin phn mm khi phi i u vi nhng yu cu thc t ca cc h phn

mm phc tp, m v phn tn.Nhng nghin cu v cng nghip pht trin phn mm trong nhng cui nm

80 v u thp nin 90 xoay quanh cch tip cn hng i tng tin ho t phng

php lun phn mm cu trc truyn thng. Phng php hng i tng c u im

so vi phng php cu trc l kh nng s dng li m ngun, d c m ngun v

x l li. tng c bn ca n l xem h phn mm nh tp hp cc thc th tng

tc gi l i tng trong mi i tng c xc nh bi ba yu t:nh danh,

trng thi v hnh vi1. Nh vy, pht trin phn mm da trn cch tip cn ny c

ngha l tin hnh xy dng m hnh ca h thng cn c pht trin (c trong ccpha phn tch v thit k) da trn khi nim i tng v nhng khi nim lin quan

nh thnh vin, phng thc, quan h... Ngn ng UML c s dng rng ri

m hnh cc h phn mm ny di dng use case, biu lp, biu tng tc...

Tuy nhin, cch tip cn hng i tng t ra khng p ng c nhu cu

pht trin cc h phn mm m, phn tn, phc tp nh qun l mng vin thng,

thng mi in t, tr gip vn phng, tm kim/lc thng tin...L mt pht trin tip

theo ca hng i tng, cch tip cn hng agent c xem l cng ngh ha hn

cho pht trin cc h phn mm phc tp ny. tng c bn ca h a agent l xemh phn mm nh mt cu trc x hi bao gm cc agent c kh nng t ch cng vi

cc tng tc c tnh cht tri thc hay mang ng ngha gia chng.

Ging nh i tng, cc agent cng c nh danh, trng thi v hnh vi nhng

nhng khi nim ny c m t mt cch tinh t hn:

Trng thi c th bao gm tri thc, lng tin, ch cn phi tho mn, cc trch

nhim c gn cho tng agent;

1Trng thi c m t bi b gi tr ca cc bin, hnh vi c m t theo cc phng thc c th c thchin t trong chnh i tng hay gi t nhng i tng khc. Tng tc gia cc i tng c m ttheo mt s cc quan h khc nhau c c gia chng.


2/192

Hnh vi l nhng vai tr m agent c th m nhim, nhng cng vic cn phi

tin hnh, cc s kin cn phi c quan st...

Cng ngh phn mm hng agent thu ht nhiu quan tm nghin cu v n c

xem l cch tip cn tin ho t cng ngh phn mm hng i tng v cng ngh

tri thc. N t ra c nhiu ha hn cho pht trin cc h phn mm trong mi

trng phn tn v m. Thp nin 90 chng kin s n r ca nhiu ng dng v

th nghim thnh cng trong cc lnh vc khc nhau nh vin thng, qun l khng

lu, cc dch v trn Internet...Nhng nm 2000, cc nghin cu v agent tp trung

vo xy dng cc phng php lun pht trin phn mm bao gm xy dng quy trnh,

cng c cng cc k thut phn tch v thit k h a agent.

Nh vy, cng ngh agent c nghin cu v pht trin mnh m trn th

gii v c p dng trong nhiu lnh vc khc nhau. Tuy nhin, nhng nghin cu trong nc v agent mi ch giai on bt u v theo hiu bit ca chng ti

nghin cu v cng ngh phn mm hng agent cha c quan tm nhiu.

Nhm p ng nhu cu nghin cu v pht trin cc h phn mm a agent,

ti tp trung xem xt quy trnh pht trin v cc k thut cho cc bc trong cc pha

phn tch v thit k h ny. Thut ng quy trnh trong ti ny c hiu l bao

gm cc bc trong cc pha phn tch v thit k phn mm. Mc d c nhiu phng

php lun v cng c pht trin h a agent c xy dng nhng phng php

lun MaSE (chi tit s c trnh by trong Chng 2) c la chn v hai l dosau y:

a. Phng php lun MaSE k tha t phng php lun hng i tng v

do s d dng hn cho nhng ngi pht trin phn mm quen thuc

vi cch tip cn hng i tng ph bin hin nay;

b. Phng php ln ny c cng c i km agentTool c th h tr pht trin

t phn tch, thit k n sinh m ngun. Hn na, trong khi cc cng c

khc tch bit khu pht trin ontology th agentTool tch hp khu ny

vo trong qu trnh pht trin v do to iu kin d dng cho ngipht trin hn v khng phi s dng cc cng c khc pht trin ontology

v hn na n li c sinh ra trong qu trnh sinh m ngun h thng.

Ni dung nghin cu ca ti bao gm:

Nghin cu cc c trng ca agent v h a agent; mt s vn c bn lin

quan n pht trin h phn mm agent bao gm xy dng ontology v tng tc;

Nghin cu cc bc trong phn tch v thit k h a agent v s dng cng c

agentTool trong cc bc ny.


3/192

Nghin cu p dng phng php lun MaSE trong phn tch v thit k h dch

v thng mi in t TraNeS.

Ti liu c t chc thnh 2 phn bao gm 7 chng nh sau:

Phn 1 C s pht trin h a agent

Chng 1: H a agent

Chng ny trnh by mt cch tng quan v agent, h a agent v cc cch tip

cn trong nghin cu xy dng cc phng php lun pht trin h a agent.

Ni dung ca chng ny tp trung xem xt cc cch tip cn khi xy dng cc

phng php lun pht trin h phn mm a agent.

Chng 2: Tng tc trong h a agent

Chng ny trc ht trnh by tng quan vn tng tc trong h a agentbao gm cc dng tng tc, tng tc vi agent trung gian v thng lng

trong h a agent. Mt m hnh thng lng song phng da trn rng buc

m s c trnh by nhm c s cho pht trin h dch v du lch s c

cp n trong cc chng tip theo.

Chng 3: Ontology trong h a agent

Ontology l khi nim quan trng nhm biu din ng ngha ca thng tin c

truyn i gia cc agent trong qu trnh tng tc. Ni dung ca chng ny tp

trung xem xt khi nim ontology v vai tr ca n trong tng tc gia ccagent. Phn k thut xy dng ontology trong h a agent s c cp trong

Chng 4.

Chng 4: Quy trnh pht trin h phn mm hng agent

Ni dung chng ny tp trung trnh by quy trnh pht trin h phn mm

hng agent da trn phng php lun MaSE cng vi cc bc tng ng

trong qu trnh pht trin da trn cng c agentTool. Cc bc pht trin

ontology ca h thng cng c gi gn trong chng ny. Mt p dng ca

quy trnh ny cho pht trin h dch v thng lng t ng s c m t chitit trong cc chng cn li.

Phn 2: p dng pht trin h dch v du lch

Chng 5: Phn tch h dch v

Chng ny nhm trnh by chi tit mt p dng ca quy trnh pht trin h a

agent cho phn tch h dch v du lch TraNeS. Ni dung cc bc phn tch

ny c trnh by gn lin vi cng c pht trin agentTool.


4/192

Chng 6: Thit k h dch v

Ni dung chnh ca chng ny l trnh by mt p dng ca quy trnh pht

trin h a agent trong thit k cho thit k h dch v du lch TraNeS.

Chng 7: Ci t v tch hp h dch v

Ni dung ca chng ny trnh by cc vn lin quan n ci t v tch hp

h dch v thng lng.

Chng 8: Gii thiu h TraNeS

Ni dung nhm im qua mt s c trng v cch tin hnh ci t ca h dch

v du lch TraNeS c pht trin trong cc Chng 5, 6 v 7.

Kt lunPhn cui cng l kt lun v mt s vn cn quan tm nghin cu hn na

trong pht trin cc ng dng.Ti liu ny c vit vi gi thit rng ngi c quen thuc vi phng php

lun pht trin phn mm hng i tng. Do , nhiu khi nim khng c nhc

li nh use case, biu tng tc, biu trng thi. Mc d nhm ti c nhiu

n lc hon thin ti liu nhng khng th trnh khi nhng thiu st. Rt mong

nhn c nhng kin ng gp v ch bo ca cc ng nghip.


5/192

MC LC

LI GII THIU.........................................................................................................1

Phn 1 C s pht trin h a agent..........................................................................3Chng 1: H a agent.....................................................................................................3Chng 2: Tng tc trong h a agent ..........................................................................3Chng 3: Ontology trong h a agent............................................................................3Chng 4: Quy trnh pht trin h phn mm hng agent.............................................3

Phn 2: p dng pht trin h dch v du lch..........................................................3Chng 5: Phn tch h dch v.......................................................................................3Kt lun............................................................................................................................4

CHNG 1 .................................................................................................................9H A AGENT............................................................................................................9

1.1 Agent................................................................................................................101.1.1 Khi nim agent.....................................................................................................101.1.2 Agent v i tng ...............................................................................................12

1.2 H a agent.......................................................................................................131.2.1 Khi nim h a agent...........................................................................................131.2.2 Mi trng tnh ton thch hp cho h a agent...................................................141.2.3 Cc ng dng ca h a agent...............................................................................15

1.3 Cc phng php lun pht trin h a agent...................................................161.3.1 Cc cch tip cn pht trin h a agent........................................................17

1.3.1.1 Cc phng php m hnh yu cu....................................................................181.3.1.2 Cc cch tip cn trong phn tch thit k h thng a agent............................19

1.4 Phng php lun Gaia.....................................................................................221.4.1 Gii thiu chung....................................................................................................221.4.2 Pha phn tch.........................................................................................................231.4.3 Pha thit k............................................................................................................23

1.5 Phng php lun MAS-CommonKADS.........................................................241.5.1 Gii thiu chung....................................................................................................241.5.2 Pha khi nim ho.................................................................................................251.5.3 Pha phn tch.........................................................................................................251.5.4 Pha thit k............................................................................................................27

1.4 Kt lun............................................................................................................28CHNG 2................................................................................................................29

TNG TC ............................................................................................................29TRONG H A AGENT...........................................................................................29

2.1 Tng quan v tng tc trong h a agent........................................................302.1.1 Ngn ng truyn thng gia cc agent..................................................................312.1.2 Cc m hnh tng tc..........................................................................................332.1.3 Tng tc vi agent trung gian.............................................................................37

2.2 Thng lng trong h a agent.......................................................................402.3 M hnh thng lng song phng................................................................42

2.3.1 C s ton hc cho thng lng song phng...................................................422.3.2 Chin lc thng lng cho agent bn...............................................................45

2.3.3 Chin lc thng lng cho agent mua..............................................................482.4 Kt lun............................................................................................................52


6/192

CHNG 3................................................................................................................53ONTOLOGY TRONG H A AGENT....................................................................53

3.1 Khi nim Ontology.........................................................................................543.1.1 Khi nim..............................................................................................................543.1.2 Ontology v c s tri thc.....................................................................................55

3.1.3 Phn loi ontology.................................................................................................563.1.4 Vai tr ca ontology trong tng tc gia cc agent............................................57

3.2 Biu din ontology............................................................................................583.2.1 Biu din ontology theo kiu hnh thc................................................................593.2.2 Biu din ontology theo kiu khng hnh thc.....................................................65

3.3 Phng php lun xy dng ontology tng qut...............................................673.4 Kt lun............................................................................................................69

....................................................................................................................................71CHNG 4 ...............................................................................................................71QUY TRNH PHT TRIN H PHN MM HNG AGENT............................71

4.1 c im ca phng php lun MaSE............................................................724.2 Quy trnh pht trin h phn mm hng agent................................................734.2.1 Khi qut cc bc pht trin................................................................................734.2.2 Pha phn tch.........................................................................................................754.2.3 Pha thit k............................................................................................................95

4.3 Kt lun..........................................................................................................105CHNG 5 .............................................................................................................107PHN TCH H DCH V.....................................................................................107

5.1 M hnh s thch ngi s dng.....................................................................108M hnh s thch v nhu cu ngi s dng l mt trong nhng vn then cht ca

pht trin cc h thng v c bit cc h dch v thng mi in t. Mc ny dnhtrnh by bi ton du lch m chng ti chn lm mu cho qu trnh pht trin h thngv sau xem xt vn m hnh s thch ngi s dng............................................108

5.1.1 Bi ton dch v du lch.......................................................................................1085.1.2 M hnh s thch ngi s dng..........................................................................109a. Rng buc cc thuc tnh..........................................................................................109b. Rng buc gia cc mt hng...................................................................................111

5.2 Phn tch h thng .........................................................................................1125.2.1 Xc nh ch ca h thng.................................................................................1125.2.2 Xy dng cc use case.........................................................................................1145.2.3 Xy dng ontology..............................................................................................117

5.2.4 Hon thin cc role..............................................................................................1195.3 Kt lun..........................................................................................................123

CHNG 6..............................................................................................................124THIT K H DCH V.........................................................................................124

6.1 Mt s vn v thit k h a agent.............................................................1256.2 Thit k h a agent .......................................................................................126

6.2.1 Xy dng cc lp agent.......................................................................................1266.2.2 Xy dng cc phin hi thoi..............................................................................1276.2.3 Hon thin cc agent...........................................................................................1326.2.4 Trin khai h thng..............................................................................................136

6.3 Kt lun..........................................................................................................136CHUNG 7..............................................................................................................137


7/192

CI T V TCH HP H THNG...................................................................1377.1 Vi nt v agentMom .....................................................................................1387.2 M hnh tch hp h thng..............................................................................140

7.2.1 UserAgent............................................................................................................1407.2.2 HotelAgent v TrainAgent..................................................................................140

7.2.3 MatchAgent.........................................................................................................1417.2.4 Hot ng ca h thng.......................................................................................142

7.3 Ci t cc lp agent.......................................................................................1437.3.1 UserAgent............................................................................................................1437.3.2 HotelAgent..........................................................................................................1497.3.3 TrainAgent...........................................................................................................1537.3.4 MatchAgent.........................................................................................................156

7.4 Kt lun..........................................................................................................159CHNG 8..............................................................................................................160GII THIU H TRANES .....................................................................................160

8.1 c trng ca H TraNeS...............................................................................1618.2 Cc m hnh hot ng ca h TraNeS...........................................................161..............................................................................................................................1638.3 Cc nhm chc nng ca H TraNeS.............................................................1658.5 Bi hc t pht trin h TraNeS......................................................................1838.6 Kt lun..........................................................................................................185

KT LUN..............................................................................................................186


8/192

PHN 1

C S PHT TRIN H AAGENT


9/192

CHNG 1

H A AGENT

Agent

H a agent

Mt s vn c bn khi nghin cu v pht trin h a agent

Cc phng php lun pht trin h a agent

Ni dung chng ny trc ht trnh by mt cch khi qut v agent, h a agent,

mi trng thch hp cho ng dng h a agent, v ba vn c bn cn quan tm khi

nghin cu v pht trin h a agent l ontology, tng tc v phng php lun pht

trin h a agent. Phn tip theo ca chng tp trung trnh by tng quan cc phng

php lun trong pht trin h a agent nhm lm c s cho xy dng quy trnh pht

trin h a agent s trnh by trong Chng 4.


10/192

CHNG 1: H A AGENT 10

1.1 Agent

1.1.1 Khi nim agent

Trong nhng nm gn y, s pht trin ca cc cng ngh Internet dn ti vic p

dng rng ri ca cng ngh thng tin vo nhiu lnh vc khc nhau ca cuc sngnh tm kim truy xut thng tin, qun l mng vin thng, thng mi in t, h tr

ra quyt nh, gii tr, S a dng ca cc lnh vc p dng khin cho vic pht trin

phn mm cng ngy cng tr nn phc tp v s phc tp ny th hin mt s c

im sau y:

Khi lng cng vic cn x l ngy cng ln: Cc h phn mm ngy nay phi x

l mt khi lng d liu rt ln hoc thao tc trn mt s lng ln cc ngun

thng tin. Bn cnh , qu trnh pht trin h thng thng xuyn phi i mt

vi cc bi ton c phc tp ln (nhiu bi ton thuc dng NP y ) c bit

l vi cc ng dng thng mi in t hay iu khin phc tp.

Yu cu v tnh chnh xc ngy cng cao: Yu cu ny xut hin cng vi s ra

i ca cc h thng i hi chnh xc v thi gian thc nh cc h iu khin

khng lu, iu khin thit b vin thng, cc bi ton qun l lu lng, qun l

tin trnh cng vic c bit, vic xy dng v trin khai cc ng dng thi gian

thc ang ngy cng tr thnh nhu cu tt yu v l mt trong nhng hng pht

trin ca cng ngh thng tin v truyn thng ni chung. Yu cu v tnh m v phn tn: Yu cu ny xut hin cng vi s pht trin ca

cc h thng mng, c bit l h thng trn mng Internet. Ngy nay, hu ht cc

h thng thng tin u gn b cht ch vi mi trng mng. Internet tr thnh

mt phn quan trng trong cuc sng con ngi v do cc phn mm cng cn

phi p ng ngy cng tt hn cc nhu cu ca con ngi nh tm kim thng tin,

h tr ngi mua v ngi bn a ra quyt nh,... v phi c tnh m, tc l c

th c cp nht, thay i hay b sung cc dch v vo h thng.

Yu cu tnh c lp cao gia cc thnh phn trong h thng: Yu cu ny thhin r nht trong cc h ra quyt nh v cc h thng mi in t. Cc h thng

ny yu cu cc thnh phn phi hot ng c lp v ch ng tng tc vi cc

thnh phn khc nhm hng ti ch ring ca mnh. Nht l trong cc h thng

m mc ch ring ca cc thnh phn l khng thng nht vi nhau, thm ch

tranh chp nhau th yu cu ny cng tr nn quan trng.

Nhng yu cu ny dn n s nghin cu v pht trin mnh m ca cng ngh

phn mm trong nhng nm gn y.Cch tip cn da trn cu trc chim u th vo

nhng nm 70-80 dn dn b thay th bi phng php lun hng i tng vi


11/192


tp k hiu chun UML m ngy nay tr thnh ph bin trong phn tch, thit k v

xy dng cc h phn mm.

Tuy nhin, khi h thng thng tin cng ngy cng phc tp th ngi ta cng

nhn ra s hn ch ca cch tip cn ny. Nguyn nhn c bn l do tnh th ng cacc i tng ngha l cc i tng ch thc s hot ng khi nhn c mt thng

ip t i tng khc. Vi cc h thng c yu cu v tnh phn tn nh cc h

thng lng trong thng mi in t, cc h qun l mng vin thngth tng

tc th ng nh vy t ra khng ph hp. Cc thnh phn phn mm trong h thng

nh vy phi phc v cho nhng dch v khc nhau v do cn phi ch ng theo

mc ch ca ring mnh ng thi phi tng tc vi cc thnh phn khc chia s

ti nguyn, yu cu h tr tnh ton...

Ta th xt mt v d sau y. Trong h dch v du lch, ngi s dng thngc nhiu yu cu khc nhau cho cc gi du lch ca mnh nh v my bay, v tu, ch

...Do , thnh phn phn mm thay mt ngi dng cn phi tng tc, thng

lng vi nhiu dch v khc mt cch t ng v sau tch hp kt qu gi li cho

ngi s dng, mi thnh phn nh th c gi l mt agent. Mc d cho n nay

cha c mt nh ngha thng nht v khi nim ny, nhiu nghin cu cho rng:

Agent l mt h tnh ton hon chnh hay chng trnh c t trong mt

mi trng nht nh, c kh nng hot ng mt cch t ch v mm do

trong mi trng nhm t c mc ch thit k.

Cc c trng c bn ca agent sau y c nhiu ngi tha nhn ([9], [13],

[14], [20] ):

Tnh t ch (autonomy): Mi agent c mt trng thi ring, c lp vi cc agent khc ( t

ch trng thi bn trong) ng thi n c th t quyt nh cc hnh ng ca mnh ( t

ch v hnh ng). T ch trang thi bn trong th hin ch: mi agent cha mt

trng thi no ca ring n, cc agent khc khng truy nhp c vo cc trng thi

ny. Cn tnh t ch v hnh ng th hin ch agent c th t quyt nh cc hnh

ng ca mnh (c th l mt hnh ng n hoc l mt chui cc hnh ng) da trn

trng thi hin thi m khng c s can thip ca con ngi hay cc agent khc. Tnh t

ch chnh l c trng quan trng nht ca agent.

Kh nng phn ng (reactivity): Tnh phn ng l kh nng agent c th nhn bit c

mi trng (qua b phn cm nhn no ) v da qua nhn bit , agent p ng kp

thi nhng thay i xy ra trong mi trng. Tnh phn ng th hin r nht cc agent

hot ng trn cc mi trng c tnh m v hay thay i nh Internet, mi trng mng

phn tn, mi trng vt l, Phn ng ca mi mt agent i vi mi trng bn ngoi

u hng ti vic thc hin mc tiu (ch) ca agent .


12/192


Tnh ch ng (pro-activeness): Khi c s thay i ca mi trng, agent khng ch phn

ng mt cch n gin m cn xc nh mt chui hnh ng cn thc hin, bn thn mi

agent s ch ng trong vic khi ng v thc hin chui hnh ng ny.

Kh nng x hi (social ability): Cc agent khng ch hng ti ch ring ca mnh mcn c kh nng tng tc vi cc agent khc trong h thng hng ti ch chung ca

h thng. Cc hot ng tng tc ny rt a dng bao gm phi hp, thng lng, cnh

tranh

1.1.2 Agent v i tng

hiu r hn khi nim agent, chng ta hy so snh agent v i tng. Trong

phng php hng i tng, cc i tng c nh ngha l cc thc th tnh ton

ng gi bao gm cc trng thi, cc hnh ng hay phng thc trong trng thi v cc i tng lin lc vi nhau thng qua vic gi cc thng ip (message).

Xt theo quan im h thng, c th xem mi agent cng l mt i tng

nhng mc tru tng cao hn. V vy, khi nim i tng c s dng trong

phn ny l ch cc i tng chun (standard object) trong phng php hng i

tng. Vi nh ngha agent c cp Mc 1.1.1 th cc i tng v cc

agent c cc im khc bit sau:

Agent c tnh t ch cao hn i tng. iu ny th hin ch cc agent

c th t quyt nh hnh ng ca mnh m khng phi l thc hin hnh ngtheo yu cu ca agent khc. Ngc li, cc i tng ch thc s hot ng khi

nhn c li gi hm t cc i tng khc. Trong cc ngn ng lp trnh hng

i tng nh Java chng hn, cc i tng c cc thnh phn ring kiu private

khng th truy nhp t cc i tng khc. Tuy nhin, cc i tng li khng th

t ch v mt hnh vi ca mnh, mt i tng vi thnh phnpublic, c th c

truy nhp bi cc i tng khc v ch khi mt i tng khc s dng cc li gi

ti cc thnh phnpublic ca i tng ny th n mi thc s hot ng.

Agent c tnh hng ch, mi agent c mt ch ring v ch ca cc

agent trong mt h thng c th thng nht hay khng tng thch vi nhau. Trong

khi cc i tng khng c mc ch ring, chng cng chia s mc ch chung

ca c h thng. Do , cc agent thng phi thng lng vi nhau trong qu

trnh tng tc.

Agent c cc hnh vi linh hot da trn cc c trng nh tnh ch ng,

kh nng phn ng v kh nng x hi trnh by trn. Cn cc i tng th

khng c cc kiu hnh vi ny.


13/192


Mi agent c mt hoc nhiu lung iu khin (thread) ring. Trong h

hng i tng cng c iu khin theo kiu lung (thread) nhng khng yu cu

mi i tng l c thread ring m ngc li c th c nhiu i tng chung mt

thread. Bn cht ca s khc nhau ny cng l c trng quan trng v mc tch ca agent so vi i tng.

1.2 H a agent

1.2.1 Khi nim h a agentKh nng ca mi agent th hin nng lc gii quyt vn ca ring agent .

Trong mt h thng c th, thng thng ti nguyn dnh cho mi agent l hn ch do

kh nng hnh ng ca mi agent cng l hn ch. Mi agent ch tp trung gii

quyt mt vn ti mt v tr c th no ch khng th gii quyt c ht cc

vn t ra cho h thng. Trong cc h phn tn phc tp, h a agent c xem lh x l thng tin c nhiu ha hn.

C th hiu h a agent l mt tp cc agent cng hot ng trong mt h

thng, mi agent c th c ch khc nhau nhng ton b h agent cng hng ti

mc ch chung thng qua tng tc.

Qu trnh tnh ton v x l thng tin trong h a agent c xem l c nhiu

u im hn so vi cc h thng khc nh h i tng [20]:

- Kh nng tnh ton hiu qu.: H a agent cung cp kh nng tnh ton hiu qu hnnh qu trnh tnh ton c phn chia cho cc agent khc nhau v kh nng phi hp

cng x l ca nhiu agent.

- tin cy cao: Do c nhiu agent cng tham gia gii bi ton v cc agent c c chtrao i, kim tra kt qu nn tin cy tnh ton trong h a agent c cho l cao

hn.

- Kh nng m rng: H a agent l h m v c th c thm cc agent mi hoc bt icc agent khi cc agent hon thnh nhim v. Kh nng ny ph hp vi tnh m ca

yu cu cc h phn mm hin nay.- Tnh mnh m: H a agent c th x l c cc bi ton ra quyt nh phc tp hoc

cc bi ton da trn thng tin khng chc chn nh cc bi ton thng lng trong

thng mi in t, cc bi ton iu khin t ng...

- Kh nng bo tr: Do h a agent gm nhiu agent, mi agent l mt module c tnht ch cao nn h a agent l h d bo tr.

- Kh nng phn ng: H a agent k tha kh nng phn ng ca cc agent n nnkhi nhn bit c mt thay i ca mi trng th cc agent trong h thng s phi

hp vi nhau a ra hnh ng tng ng vi thay i .


14/192


- Tnh linh hot: Cc agent trong h a agent c kh nng khc nhau c th tng tcvi nhau cng gii quyt mt vn chung. Mt agent trong h thng khng phi

ch agent khc m ch ng tng tc tm ra thng tin cn thit gii quyt vn

t ra cho ring mnh.

Kh nng s dng li: H a agent c kh nng s dng li v mi agent c kh nng

ring v c th dng li cho nhiu ng dng khc nhau.

1.2.2 Mi trng tnh ton thch hp cho h a agent

H a agent t ra c nhiu u im trong vic gii quyt cc bi ton phc tp hin

nay da trn tnh nng ca tng agent v s phi hp gia cc agent. Cc mi trng

v dng bi ton thch hp cho h a agent bao gm [20]:

H a agent c th gii quyt mt bi ton vt qu kh nng ca mt agent n. Trongh s dng mt agent n, h thng thng tp trung tt c cc x l cho mt agent duy

nht. Nhng do ti nguyn ca mt agent n l hn ch (chng hn nh ng truyn

hay b nh) nn cc h thng nh vy thng c nhng nt c chai, gy nghn

mng hoc tnh trng b tc khi c qu nhiu yu cu tp trung v mt agent. H a

agent gii quyt vn ny thng qua c ch phi hp, cng tc gia cc agent.

H a agent cung cp phng php gii quyt cc bi ton phn tn trong c nhiu

thnh phn t ch cng hot ng trong mt x hi agent (society of agent) v cng tun

theo cc lut x hi (social law) trong x hi . Cc thnh phn trong cc h a agent

khng phi lun lun c cng chung mt ch. thc hin cc ch ring ca mnh,cc agent c th tng tc vi cc agent khc theo cc giao thc tng tc nh: phi

hp, cng tc, hoc trong trng hp mc ch ring mu thun nhau th c th l cnh

tranh, thng lng.

H a agent cung cp phng php gii quyt cc bi ton m thng tin c thu thp t

nhiu ngun khc nhau. Cc ngun thng tin ny c bn cht phn tn trong mt h

thng rt ln. V d c th cho dng bi ton ny chnh l bi ton truy xut thng tin

trn internet, cc bi ton tch hp v x l thng tin

Mt dng bi ton khc rt ph hp vi h a agent l bi ton tch hp h chuyn gia.Mi h chuyn gia l mt h thng tp trung gii quyt mt vn xc nh da trn tri

thc ca chuyn gia v vn . Thc t c th c nhiu h chuyn gia tuy hng ti

gii quyt cng mt vn nhng li phn tn nhng v tr rt xa nhau. H a agent

cung cp kh nng phi hp gia cc h chuyn gia ny nng cao kh nng x l ca

h thng.

Cch tip cn hng agent ph hp khi h thng yu cu cc kiu lin lc phc tp, a

dng. V d nh cc h thng s dng c ch lin lc ca con ngi hoc tng tc gia

cc thc th hn tp.


15/192


Cch tip cn hng agent ph hp cc h thng cn phi thc hin tt trong tnh hung

khng th m t hnh vi ca cc thnh phn trong h thng mt cch r rng theo dng

tng trng hp (case-by-case).

Cch tip cn hng agent cng t ra ph hp trong tnh hung c s thng lng,cng tc hay cnh tranh gia cc thc th khc nhau trong h thng. V d nh cc tc

v khc nhau vi cc ch xung t nhau c th cn phi thc hin ng thi, khi s

c cc qu trnh cnh tranh hay thng lng gia cc thnh phn.

Cch tip cn hng agent cng ph hp khi h thng phi hnh ng mt cch t ch

thay mt ngi dng, v d nh trong cc qu trnh thng lng gia cc thnh

phn bn trong h thng t ti nhng mc ch khc nhau.

1.2.3 Cc ng dng ca h a agent

Trong nhng nm gn y, cc h a agent ngy cng tr nn ph bin v c pdng trong nhiu h thng khc nhau. Theo Jennings et al. [23], cc ng dng ca h

a agent c th chia thnh cc nhm sau:

Cc h ng dng trong cng nghip

Cc ng dng h a agent trong cng nghip l nhng ng dng u tin ca lnh vc

nghin cu ny. Hin nay, agent c p dng rng ri trong cc dng h thng nh:

- H sn xut: trong cc h a agent ng dng trong sn xut, cng vic s c phn

chia thnh cc nhm cng vic hoc cc cng vic nh hn vo giao cho cc agentthc hin. Cc agent cn c c ch lp k hoch v phi hp (tng tc) ln nhau

hon thnh cng vic c giao.

- H thng iu khin tin trnh: Cc h iu khin tin trnh c vai tr rt ln trongcng nghip. H a agent trong h thng ny s c xem nh mt b iu khin

tin trnh (process controller) vi tnh t ch v linh hot iu khin hot ng

ca tin trnh .

- H thng vin thng: cc h thng vin thng thng l cc h thng ln, phn tn,

yu cu qu trnh gim st v qun l theo thi gian thc (nh qun l mng vinthng, gim st hot ng ca thit b). Cc ng dng ny rt ph hp vi h a

agent.

- Ngoi ra, h a agent cng c p dng trong cc h thng qun l khng lu vqun l lu lng giao thng. y l cc h qun l yu cu tnh thi gian thc cao,

cc thnh phn trong h thng phi c tnh t ch v linh hot trong x l tnh

hung.

Cc ng dng trong thng mi

Trong thi gian gn y, h a agent ngy cng c p dng nhiu trong thng miin t. Vi cc h ng dng ny, vic trao i mua bn din ra thun li v hiu qu


16/192


hn cho c ngi bn, ngi mua cng nh cc nh sn xut. Cc h ng dng agent

trong thng mi bao gm:

- H qun l thng tin: Cc h thng ny thc hin vic lc, tch v thu thp thng

tin cn thit dng trong thng mi. H thng thng xuyn phi x l mt khilng thng tin rt ln nhm cung cp cho ngi dng nhng thng tin cn thit.

- Cc h thng mi in t: Cc agent trong cc h thng mi in t s i dincho ngi bn, ngi mua cng nh ngi mi gii trong cc giao dch in t. Cc

agent ny t trao i vi nhau thng qua cc chin lc thng lng ca mnh.

y chnh l xu hng pht trin ca thng mi in t hin nay.

- Cc ng dng qun l tin trnh kinh doanh. Qun l tin trnh kinh doanh nhmgip cho ngi qun l ra quyt nh trong mt tnh hung c th hoc thc hin

mt cng vic c th no vi s h tr ca tt c cc thnh vin trong n v. Cc

agent s i din cho cc thnh vin thc hin cc vai tr xc nh. Cng vic s

c phn chia cho cc nhm thnh vin da trn c ch tng tc gia cc agent.

Cc ng dng gii tr

Cc h a agent cng c s dng xy dng cc ng dng gii tr nh cc tr

chi in t v cc ng dng khc nh nh ht hay rp chiu phim tng tc (Interactive

Theatre and Cinema).

Cc ng dng trong y t

- ng dng gim st bnh nhn. Cc agent hot ng nh cc chuyn gia theo dihoc chn on bnh cho ngi bnh. Vic chn on bnh c thc hin thngqua c ch lp lun ca agent.

- Cc ng dng chm sc sc kho (Health Care). H a agent c thit k thchin cc nhim v ca mng li y t cng ng.

1.3 Cc phng php lun pht trin h a agent

Trong nghin cu pht trin h a agent ba vn sau y c quan tm xem xt:

Tng tc gia cc agentTrong cc h a agent, mi agent l mt thnh phn ch ng v hng ti ch

ring nn cn phi trao trao i thng tin-tri thc vi nhau v thng lng vi

nhau khi cn thit. Qu trnh trao i, tng tc gia cc agent khng th ging vi

dng tng tc th ng (thng qua cc li gi hm) trong h hng i tng.

Vn tng tc gia cc agent c xem l then cht trong pht trin h a agent

v s c trnh by chi tit trong Chng 2.

Ontology


17/192


cc agent tng tc vi nhau thng qua vic gi v nhn cc thng ip truyn

thng ging nh cc i tng. Tuy nhin, cc thng ip ny khng biu din cc

li gi hm n gin m cn phi biu din c thng tin v tri thc trao i gia

cc agent. Mi agent trong h a agent c th c mt min quan tm ring, ccagent hiu nhau trong qu trnh trao i cn mt cu trc ng ngha gi l

ontology. Ontology v xy dng ontology biu din thng tin v tri thc trong

h thng s c trnh by chi tit trong Chng 3.

Phng php lun pht trin h a agent

Xy dng h a agent cn phi theo quan im no v cc bc no? Do xut pht

im ca cc nh nghin cu khc nhau (hoc l t cng ng tr tu nhn to hoc

l t gii nghin cu hng i tng) nn c nhng quan im khc nhau v pht

trin h a agent. iu ny dn ti vic c nhiu phng php lun pht trin h aagent khc nhau; hoc da trn phng php lun truyn thng hng i tng

hoc da trn cng ngh tri thc hoc c hai. Tng quan cc phng php lun

pht trin h a agent s c cp tip theo trong phn ny.

1.3.1 Cc cch tip cn pht trin h a agent

Nhu cu pht trin cc ng dng phn mm da trn cng ngh agent trong nhng

nm gn y dn n s ra i ca nhiu phng php lun da vo ba cch tipcn sau y: (1) cch tip cn da trn agent v cng ngh agent, (2) cch tip cn

pht trin t hng i tng v (3) cch tip cn da trn cng ngh tri thc. Ni

dung phn cn li ca chng ny trc ht trnh by cc cch tip cn xy dng h a

agent v mt s phng php lun c pht trin da trn cc cch tip cn .

Sau , chng ti s tp trung trnh by khi qut hai phng php lun i din cho

hai cch tip cn (1) v (2) l Gaia v MAS-CommonKADS.

Qu trnh pht trin mt h thng phn mm thng thng bao gm cc pha

chnh sau y: Xc nh yu cu

Phn tch

Thit k

Ci t v tch hp

Trong cc pha trn th phn tch v thit k h thng c xem l cc pha chnh th

hin quan im ca ngi pht trin v h thng ca mnh. Phn tip theo s trnh by

mt s phng php m hnh yu cu ca ngi s dng, cc cch tip cn trong phn


18/192


tch v thit k h a agent; phn ci t v tch hp cho mt p dng c th s c

trnh by trong chng 7 ca ti liu ny.

1.3.1.1 Cc phng php m hnh yu cu

Vic xc nh yu cu h thng l cng vic u tin cn thc hin khi xy dng mt

h a agent. Phng php m hnh yu cu nhm m hnh v phn tch cc yu cu

chc nng cng nh cc yu cu phi chc nng ca h cn pht trin. Tp cc yu cu

cn phi c kh nng biu din y v chnh xc cc rng buc ca h thng trn

thc t; n ng vai tr quan trng trong vic gim st cc thay i c th c trong

ton b qu trnh phn tch thit k sau ny.

Theo Weiss [37], c hai hng khc nhau trong vic m hnh ho yu cu h

thng: (1) m hnh yu cu hng agentv (2) m hnh yu cu hng ch (goal).Chng ta s ln lt xem xt hai k thut ny.

Phng php m hnh ho yu cu hng agent

M hnh yu cu hng agent da trn hai c im:

Mi agent l mt phn mm c th c kh nng hot ng t ch v hng ti

ch ring ca mnh.

Agent c xy dng da trn vic m hnh qu trnh nhn thc v lp lun ca

con ngi.Nh vy, mi yu cu cn phi xc nh c: h a agent nhm mc ch gii quyt

nhng vn g; cn phi m hnh ho nhng tri thc no v nht l m hnh ho c

ch lp lun ca agent da trn nhng c s no. Cc phng php i din cho kiu

m hnh ny gm:

i*: y l c s m hnh ho tp yu cu thng qua cc thuc tnh nh (intention)

nh mc ch (goal) hay tho thun (commitment). Cc yu cu s c nhm theo

cc thuc tnh nh ny v thng qua qu trnh m hnh ho chuyn sang giai

on phn tch (v c t) yu cu.ALBERT (Agent-oriented Language for Bulding and Eliciting Real-Time

requirement) v ALBERTII. y l cc k thut xc nh yu cu tp trung vo khi

nim agent. ALBERT ng thi cng l mt ngn ng c t yu cu theo kiu

hnh thc.

Hai kiu m hnh ho i* v ALBERT c th p dng ring bit hoc kt hp vi nhau.

M hnh yu cu trong phng php lun Tropos ([2]) chnh l v d ca vic kt hp

hai kiu ny.

Phng php m hnh ho yu cu hng ch


19/192


ch (goal) l khi nim tr li cu hi h thng hng ti ci g. Phng php m

hnh ha yu cu hng ch s xc nh cc yu cu chc nng v phi chc nng theo

phng php sau:

Yu cu chc nng s c thu thp v nhm theo tr li ca cc cu hi ci g.Tc l cn phi tr li cc cu hi nh h thng hng ti thc hin cc cng

vic g? cc thnh phn no cn c trong h thng? cc rng buc ca h

thng l g?.

Cc yu cu phi chc nng nhm m hnh ho cc cu hi ti sao, th no nh

h thng thc hin nhim v ca mnh nh th no, ti sao cn h a agent?

Cc v d ca phng php m hnh ho yu cu hng ch:

KAOS(Knowledge Acquistion in automated Specification): l mt khun mu chung

m hnh ho yu cu da trn tnh hng ch ca agent.

NFR (Non-Functional Requirement): Tp trung vo vic c t v lp lun lin quan

n cc yu cu phi chc nng. NFR cng xy dng phng php biu din cc yu

cu softgoal, v d nh cc goal khng nh ngha mt cch r rng c, cc goal m

t yu cu tho mn rng buc...

1.3.1.2 Cc cch tip cn trong phn tch thit k h thng a agent

Theo [37] cc phng php lun phn tch v thit k h a agent u c xy dng

da trn mt trong ba cch tip cn (Xem Hnh 1.1):

- Da trn agent v cng ngh agent

- Pht trin t phng php hng i tng

- Da trn cng ngh tri thc.


20/192


Cch tip cn theo agent v cng ngh agent

Cc nghin cu xy dng phng php lun pht trin h a agent theo cc c

trng ca agent v cng ngh agent xut pht t cc nhn nh sau:

-

Agent c nhng c trng ring nh tnh t ch, tnh ch ng v khnng phn ng. Cc c trng ny l khc hon ton khc vi i tng v to

cho agent kh nng tng tc ch ng v kh nng suy lun m cc i tng

khng c. V vy, khng th m hnh ho agent bng cch s dng cc phng

php lun dnh cho hng i tng.

- Agent hot ng nh mt x hi vi cc lut chi phi ring nn c th

xem xt agent t kha cnh x hi v s dng cc khi nim tru tng mc x

hi m hnh ho cc agent trong h thng.

Cc khi nim tru tng mc x hi c s dng m hnh ho agent theocch tip cn ny bao gm agent, nhm (group), t chc (organization) ... Mc

tru tng x hi c xem nh l mt mc tru tng cao hn so vi mc i

tng thng thng v ph hp vi vic biu din cc agent v x hi cc agent

bao gm cc thnh phn c tnh phn ng, linh hot v tng tc ch ng.

Da trn cc khi nim tru tng mc x hi m phng php lun ny

nh ngha cc bc, cc pha ca ton b qu trnh pht trin h thng. Thng

thng, vi cch tip cn ny, qu trnh pht trin h thng c phn thnh hai

pha tch bit: pha phn tch v pha thit k. Pha phn tch tng ng vi m

Phng php lun pht trinh a agent

Cch tip cn datrn Agent v Cng

ngh Agent:Cc khi nim tru tng

mc x hi: Agent, nhm,t chc

Cch tip cn phttrin t hng i

tngAgent: object c mc

tru tng cao hn.M rng UML

Cch tip cn theoCng ngh tri thcDa trn qu trnh nhn

dng, thu nhn v m

hnh ho tri thc

Hnh 1.1: Cc cch tip cn xy dng phng php lun a agent


21/192


hnh t chc (organization model) cn pha thit k ng vi m hnh agent

(agent model). Tiu biu cho cc phng php lun thuc loi ny l cc

phng php lun Gaia, SODA, AALAADINPhng php lun Gaia s

c gii thiu chi tit hn trong phn 1.4.Cch tip cn pht trin t phng php hng i tng.

Khc vi cch tip cn trn, cch tip cn pht trin t phng php hng i

tng da trn quan im cho rng cc k thut c pht trin v c p

dng rng ri cho cng ngh phn mm hng i tng c th c m rng

cho cc phn mm hng agent.

Cch tip cn ny xem mi agent cng l mt i tng nhng mc tru

tng cao hn. Cc cng c s dng biu din i tng v phn tch thit

k h thng hng i tng nh UML hon ton c th m rng biu dincc c trng ring ca agent. Cc nghin cu xy dng phng php lun pht

trin t phng php lun hng i tng tp trung vo cc cng vic sau:

- Pht trin cc cng c da trn nn tng sn c ca hng i

tng p dng cho h a agent, v d nh m rng UML thnh AUML

(Agent UML).

- B sung cc bc, pha mang tnh c trng ca agent v cng

ngh agent nh ch (goal), vai tr (role) v ontology.Tiu biu cho cc phng php lun ny l cc phng php lun MaSE,

MASSIVE, KGR...

Cch tip cn da trn cng ngh tri thc

Da trn quan im cho rng qu trnh m hnh tri thc ring ca mi agent v

s trao i tri thc gia cc agent trong h thng chnh l c s ca mi hot

ng ca h thng, cc nghin cu theo cch tip cn ny s dng cc khi

nim v qu trnh trong cng ngh tri thc xy dng nn phng php lun

cho h a agent.Cc phng php lun ny tp trung vo cc qu trnh thu thp tri thc

(Knowledge acquisition), m hnh tri thc (Knowledge modelling) v lp lun

c s dng bi cc thnh phn agent trong h thng phn mm. Tiu biu

cho cch tip cn ny l cc phng php lun nh CoMoMAS, MAS-

ComonKADS.

Nh vy, c ba cch tip cn trong phn tch v thit k h a agent. Mi cch tip cn

li c nhng u im ring. hiu nhng im khc bit ca cc phng php luntheo cc cch tip cn ny, phn cn li ca chng ny dnh trnh by v phng


22/192


23/192


chnh l tru tng v c th. Cc khi nim tru tng bao gm role, quyn hn

(permission), trch nhim (responsibilities), giao thc (protocol), hot ng

(activities) cn cc khi nim c th l kiu agent (agent type), dch v (service)

hay thu thp tri thc (acquaintance).Ta s ln lt xem xt chi tit cc pha phn tch v thit k trong Gaia.

1.4.2 Pha phn tch

Mc ch ca pha phn tch l pht trin mt hiu bit c bn v h thng v cu trc

ca n (khng xt chi tit n vic ci t h thng). Hiu bit ny c biu din theo

cu trc t chc ca h thng. Chng ta c th xem cu trc t chc ca mt h thng

bao gm mt tp cc role, cc mi quan h gia cc role v tng tc gia cc role .

Khi nim role trong Gaia bao gm bn thuc tnh: trch nhim

(responsibilities), quyn hn (permissions), hot ng (activities) v giao thc

(protocols).Trch nhim xc nh cc yu cu chc nng ng vi role . Quyn hn

ca mt role gip nhn ra cc trch nhim thng qua vic xc nh cc ti nguyn sn

sng cho role . Cc hot ngca role l cc tnh ton lin kt vi role m agent c

th c th tin hnh m khng cn tng tc vi agent khc. Mi role cng c nh

ngha bi mt sgiao thc, mi giao thc xc nh role phi tng tc vi cc role

khc nh th no.

Da trn yu cu, pha phn tch s tin hnh xy dng m hnh role v m hnhtng tc gia cc agent trong h thng.

M hnh role nhm xc nh cc role ca h thng v c biu din mt cch

tru tng theo hai thuc tnh:

- Cc quyn hn ng vi role

- Cc trch nhim ca role

M hnh tng tc xc nh s ph thuc v cc mi quan h gia cc role

trong t chc a agent. Mi giao thc tng tc kt ni 2 role s c nh ngha c

th trong m hnh ny. Tng tc trong m hnh ny c xem xt theo bn cht tnhin v mc ch ca tng tc ch khng phi da trn vic gi v nhn cc thng

ip.

1.4.3 Pha thit k

Mc ch ca pha thit k trong Gaia l chuyn cc m hnh trong pha phn tch sang

mc tru tng thp hn (tng t nh trong thit k hng i tng) nhm hng

ti vic ci t h thng. Ni cch khc, pha thit k nhm tr li cu hi lm th no

x hi cc agent thng qua tng tc t c ch ca h thng, v ring vi ccagent th cn nhng g t c iu .


24/192


Pha thit k trong Gaia bao gm ba m hnh: m hnh agentxc nh cc kiu

agent trong h thng v cc agent c th trong h thng s l cc th hin ca cc kiu

agent ny; m hnh dch v xc nh cc dch v chnh cn c thc hin cc role

trong kiu agent tng ng; cn m hnh thu thp tri thc nhm biu din lin lc giacc agent khc nhau. Ta s xem xt c th tng m hnh:

M hnh agent

Mc ch l xc nh cc kiu agent c th s dng trong qu trnh pht trin h thng.

Mt kiu agent l mt tp cc role. Trn thc t c th tn ti cc tng ng 1-1 gia

cc role v cc kiu agent. Tuy nhin, iu ny l khng bt buc, ngi thit k c

th chn mt s role mt s role c lin quan vo trong cng mt kiu agent cho ph

hp.

Vi mi kiu agent, ngi thit k c th xc nh s agent th hin c th cthng qua mt ch gii ghi bn di tn lp agent nh sau. Nu s ch gii c dng l

mt s n th s c chnh xc n th hin, nu l m..n th s c t nht l m v nhiu nht

l n th hin, nu l * c th c 0 n nhiu th hin, cn nu l + th c ngha l c t

1 n nhiu th hin.

M hnh dch v

Xc nh cc dch v kt hp vi mi role v c t cc thuc tnh chnh ca dch v

. C th xem mi dch v l mt chc nngca agent. Mi dch v s c cc thuc

tnh nh u vo, u ra, cc iu kin u vo (pre-conditions) v cc iu kin u

ra (post-conditions). Cc iu kin u vo v u ra xc nh cc rng buc cho dch

v .

M hnh thu thp tri thc

Xc nh cc lin lc gia cc kiu agent tn ti. M hnh khng xc nh thng

ip g c gi i v khi no gi i, m ch n gin l ch ra cc phin lin lc ang

tn ti. Mc ch ca m hnh ny l nhm pht hin ra cc nt c chai c th c

trong thi gian hot ng ca h thng. Mt m hnh c dng nh mt th vi cc

node l cc kiu agent.

1.5 Phng php lun MAS-CommonKADS

1.5.1 Gii thiu chung

MAS-CommonKADS [21] l phng php lun m rng t CommonKADS p

dng cho phn tch v thit k h a agent. y l mt phng php lun theo cch

tip cn da trn cng ngh tri thc. Phng php lun ny thm vo CommonKADS

cc k thut ca phn tch thit k hng i tng nh k thut m hnh ho i

tng (Object Modelling Technique: OMT), thit k hng trch nhim(Responsibility Driving Design: RDD) v cc k thut m t giao thc agent nh


25/192


ngn ng m t v c t (Specification and Description Language: SDL) v biu

thng ip tun t (Message Sequence Charts). MAS-CommonKADS a ra cc m

hnh sau:

- M hnh agent (Agent model: AM): biu din cc c tnh ca agent nh: khnng lp lun, cc dch v, cc nhm agent v cc s phn cp cc agent.

- M hnh task (Task model: TM): biu din cc task m agent c th tin hnh,

cc ch (goal), cc thnh phn

- M hnh chuyn gia (Expert model: EM): biu din tri thc cn cho agent

t c ch ca n t ra.

- M hnh t chc (Organisation model: OM): biu din cu trc t chc x hi

trong h a agent cn xy dng.

- M hnh phi hp (CoM): biu din cc phin hi thoi gia cc agent, cc

tng tc v cc giao thc tng tc tng ng.

- M hnh lin lc (Communication model: CM): biu din chi tit cc tng

tc gia con ngi vi h thng a agent.

- M hnh thit k (Design model: DM): tp hp t cc m hnh trc

thit k h thng. Bao gm ba m hnh nh: thit k mng, thit k agent v

thit k nn.

Cc bc pht trin h a agent theo phng php lun MAS-CommonKADS baogm 3 pha chnh l: pha khi nim ho, pha phn tch v pha thit k. Chng ta s ln

lt xem xt cc pha ny.

1.5.2 Pha khi nim ho

Nhim v chnh ca pha ny l m t bi ton thng qua cc biu use cases v

scenario c dng tng t nh trong phn tch hng i tng. Cc biu ny gip

chng ta hiu r cc yu cu phi hnh thc ca h thng v kim tra h thng v sau.

Mi thnh phn tham gia vo cc use case v biu tun t c gi l mt role.1.5.3 Pha phn tch

Mc ch ca pha phn tch l c t cc yu cu ca h thng vo trong cc m hnh

c ch ra trong phn 1.5.1 tr m hnh thit k. Qu trnh xy dng cc m hnh ny

c m t ngn gn nh sau.


26/192


Xy dng M hnh agent

Cc agent s c xc nh theo cc chin lc sau:

- Phn tch cc thnh phn tham gia vo cc use case xc nh trong pha khi nim

ho nhm cc role tng t nhau vo trong mt agent nhm n gin ho cc traoi, lin lc trong h thng.

- Phn tch cc cu trong m t bi ton tm ra cc ch ng l cc i tng ch

ng v gn chng thnh cc agent. Cc hnh ng ca cc ch ng ny s tr thnh

ch ca agent nu nh hnh ng do agent khi to, v s tr thnh dch v ca

n nu nh hnh ng c thc hin theo yu cu bn ngoi.

- S dng chin lc heuristics: cc agent s c xc nh thng qua cc khi nim

v khong cch nh: s phn tn tri thc, phn tn v a l, phn tn v mt logic

hoc phn tn v t chc.- S dng m hnh chuyn gia xc nh cc chc nng v cc yu cu v nng lc

x l tri thc, thng qua nh ngha cc agent.

- S dng th CRC v k thut RDD ging nh trong thit k hng i tng.

Xy dng M hnh Task

Cc task c xc nh theo cch tip cn t trn xung v c biu din theo dng

hnh cy. M t mt task bao gm tn ca task, u vo v u ra ca task, cu trc

ca task, cc iu kin thc hin,

M hnh ny gip ngi pht trin h thng d dng qun l cc thay i trong

cc bc cn li ca pha phn tch cng nh trong pha thit k.

Xy dng M hnh phi hp

M hnh phi hp c xy dng theo 2 pha:

- nh ngha cc knh truyn thng gia cc agent v xy dng mt bn mu

(prototype).

- Phn tch cc tng tc v ch ra cc tng tc phc tp cng vi cc giao thc phi

hp tng ng.Mi pha bao gm mt lot cc bc nh, trong s dng cc k hiu theo MSC

(Message Sequence Chart), SDL (Specification and Description Language) hoc biu

din thng qua cc cu trc tri thc (tham kho thm trong [21]).

Xy dng M hnh tri thc

Ngi pht trin s s dng m hnh chuyn gia m hnh ho kh nng lp lun ca

cc agent trong vic thc hin cc task v hng ti ch ca n. y ch c mt s

m hnh chuyn gia c xy dng nhm m hnh ho kh nng lp lun trong min

tri thc v m hnh ho kh nng suy lun ca agent.


27/192


M hnh chuyn gia biu din cc tri thc ng dng (bao gm tri thc min, tri

thc lp lun, v tri thc tc v) cng vi tri thc gii quyt bi ton. Qu trnh xy

dng m hnh tri thc s ln lt xem xt v biu din cc tri thc ng dng v cc tri

thc gii quyt bi ton.

Xy dng M hnh t chc

Tng t nh trong CommonKADS, m hnh t chc trong MAS-CommonKADS

cng c xy dng biu din cc mi quan h tnh hoc c cu trc ho gia

cc agent (trong khi m hnh phi hp biu din cc mi quan h ng).

M hnh t chc cng s dng tp k hiu theo OMT nhng vi ng ngha

thay i cho ph hp vi h a agent.

1.5.4 Pha thit k

Da trn tp cc agent cng vi cc m hnh c xy dng trong pha phn tch,pha thit k s tin hnh xy dng m hnh thit k. Pha ny bao gm cc bc nh

sau:

- Thit k kin trc mng agent (agent network design)

- Thit k agent (agent design)

- Thit k nn (platform design)

Ta s ln lt xem xt tng bc ny.

Thit k kin trc mng agentBc ny xc nh c s h tng cho h a agent bao gm cc iu kin cn thit v

mng, v tri thc v cc s phi hp gia cc thnh phn trong h thng. Cc agent

cng s c nh ngha trn c s h tng ca h thng ph thuc vo mt s iu

kin cn thit theo yu cu sau:

- Cc iu kin v mng: bao gm dch v t tn agent, dch v ng

k, mc bo mt, m ho v chng thc, cc giao thc truyn thng v ng

dng...

-

Cc iu kin v tri thc: bao gm cc ontology server, cc b chuyni ngn ng m t tri thc...

- Cc iu kin v s phi hp gia cc thnh phn trong h thng: bao

gm cc giao thc phi hp, cc dch v qun l nhm agent...

Kt qu ca bc thit k kin trc mng agent l cc agent phi lin lc c vi

nhau thng qua cc giao thc tng tc v ontology ca h thng.

Thit k Agent

Bc ny xc nh kin trc ph hp nht cho mi agent da theo cc module: lin

lc vi ngi dng (user-communication), lin lc gia cc agent (agentcommunication), nng lc x l v cc dch v ca h thng.


28/192


Thit k nn

Bc ny la chn mi trng pht trin cho h a agent v cc phn cng cn thit

cho h thng nu cn.1.4 Kt lun

Chng ny trc ht tp trung trnh by nhng nt khi qut v agent, h a agent,

nhng ng dng ca h a agent. Mt s so snh gia agent/h a agent v i

tng/h i tng cng c im qua nhm lm sng t hn cc khi nim ny.

Tip theo l im qua mt s vn quan trng khi nghin cu v pht trin h

agent: ontology, tng tc v cc phng php lun. Phn quan trng ca chng ny

l trnh by tng quan cc phng php ln pht trin h a agent nhm lm c s

cho xy dng quy trnh pht trin h a agent da trn phng php lun MaSE m sc trnh by chi tit trong Chng 4.


29/192

CHNG 2

TNG TCTRONG H A AGENT

Tng quan v tng tc trong h a agent

Thng lng trong h a agent

M hnh thng lng song phng

Chng ny tp trung trnh by vn tng tc trong h a agent. Trc ht s

cp tng quan v vai tr tng tc trong h a agent v ngn ng truyn thng c sdng trong qu trnh trao i thng tin v tri thc gia cc agent. Phn tip theo s

trnh by cc m hnh tng tc trong h a agent v c bit tp trung xem xt m

hnh thng lng song phng vi rng buc m nhm lm c s cho pht trin h

dch v du lch TraNeS s c trnh by trong cc chng 5, 6, 7, 8.


30/192

CHNG 2: TNG TC TRONG H A AGENT 30

2.1 Tng quan v tng tc trong h a agent

H a agent bao gm nhiu agent t ch c th hot ng trn nhng my tnh khc nhau.

Tuy nhin, cc agent thng phi trao i, tng tc vi nhau v chnh cc tng tc

trong h a agent quyt nh kin trc ca h thng . Cc dng tng tc ny phc tphn rt nhiu so vi cc tng tc trong h i tng. Cc agent tng tc vi nhau bng

cch gi thng ip v bn cht ca cc thng ip ny cng l nhng li gi hm nh

trong h cc i tng nhng cc li gi trong tng tc gia cc agent c nhiu khc

bit so vi tng tc gia cc i tng:

Cc tham s c th c kiu c nh ngha trong mt cu trc ng ngha gi l

ontology.

Cc tham s c vit theo mt dng thng ip truyn thng c nh ngha bi

mt ngn ng truyn thng agent (nh KQML hoc FIPA-ACL).

Ni dung ca thng ip trong tng tc a agent c th rt phc tp nh mt chui

cc hnh ng hoc cc yu cu

Ngoi s khc nhau v dng ca cc i s, tng tc trong h a agent cng khc tng

tc gia cc i tng do bn cht khc nhau gia i tng v agent. Agent l thnh

phn c tnh t ch v hnh ng hng ch ch khng th ng nh cc i tng.

Vi mi h agent c th c xy dng th mc ch chung ca h thng v mc

ch ring ca tng agent c th khc nhau, thm ch khng tng thch nhau. V d trongh thng mi in t, nu agent mua c nhim v mua c hng vi gi cng r cng

tt th agent bn li c mc ch l bn vi gi cng cao cng tt. S thng nht v mu

thun v mc ch ca cc agent trong h thng dn n s a dng ca cc m hnh

tng tc trong h a agent. Nh vy, tng tc trong h a agent c nhng c trng

ring khc bit so vi tng tc a i tng. Vai tr ca tng tc trong h a agent c

th c tng kt nh sau:

Thng qua tng tc, mi agent s thu thp thng tin v tri thc nhm t c ch

(goal) ring ca mnh v hng ti ch chung ca c h thng. Tng tc to nn tnh ng cho h a agent. Qua tng tc, h thng c th c m

rng hay thu hp mt cch d dng, nht l vi cc h a agent s dng agent trung

gian.


31/192


Qu trnh tng tc khng ch din ra gia cc agent m cn c th din ra gia cc

h agent khc nhau. Khi , kh nng phi hp gia cc h thng gii quyt cc

vn phc tp tng ln nhiu ln.

Tng tc gia cc agent quyt nh kin trc v hot ng ca h a agent . Thngqua vic xem xt cc tng tc cn c gia cc agent, ngi thit k h thng c th

xy dng kin trc h thng v phn tch nhim v mt cch r rng cho tng agent.

Tng tc gia cc agent gip tch hp cc ngun thng tin trong h thng. Trong h

tch hp thng tin, mi agent i din cho mt ngun thng tin nht nh. Cc ngun

thng tin ny thng l khng ng nht, c biu din theo nhng cch khc nhau.

Thng qua tng tc, thng tin gia cc ngun s c tch hp thu c

nhng thng tin cn thit.

Ba vn sau y cn quan tm xem xt khi nghin cu v tng tc trong h a agent:

1. M hnh tng tc: Tu thuc vo mc ch ca h thng c th m ngi pht trin h

thng phi la chn mt m hnh tng tc ph hp, m hnh tng tc ny s quy nh

kin trc ca h thng cng nh hnh vi ca cc agent trong h thng.

2. Ngn ng truyn thng s dng trong cc thng ip: Khi hot ng trong cng mt h

thng vi nhau cc agent phi s dng chung mt ngn ng truyn thng. Ngn ng ny

khng ch quy nh cu trc thng ip m cn quy nh cc dng thng ip hi v tr

li trong cc phin hi thoi.3. Ontology v s dng ontology trong tng tc a agent: Mi agent trong h thng l mt

thnh phn phn mm ring bit, do , min tri thc quan tm ca cc agent trong mt

h thng c th khc nhau. cc agent c th hiu nhau trong qu trnh trao i th h

thng phi s dng ontology nhm biu din cc khi nim m t min v mi quan h

gia cc khi nim .

Phn 2.1.1 s trnh by nhng nt chung v ngn ng truyn thng a agent. Cc m hnh

tng tc s c trnh by trong phn 2.3. Ontology s c trnh by trong chng 3.

2.1.1 Ngn ng truyn thng gia cc agentCc agent trao i vi nhau thng qua cc thng ip. Khc vi h hng i tng,

thng ip trong h a agent khng ch biu din cc li gi hm m cn phi biu din

thng tin v tri thc cn trao i gia cc agent. Cc thng ip ny c biu din theo

cc ngn ng truyn thng agent (ACL: Agent Comminucation Language) nhm mc

ch:


32/192


nh ngha khun dng cc thng ip trao i gia cc agent trong h

thng.

Thit lp mt giao thc trao i gia cc agent, bao gm: nh ngha cc

kiu thng ip gi v nhn, cc m hnh trao i thng ip gia cc agent.Cc ngn ng truyn thng u da trn l thuyt hnh ng - li ni (speech-act) ([11]).

Mi thng ip bao gi cng phi m t y ngi gi, ngi nhn, mc ch ca li

ni v ng ngha ca li ni. Mt hnh ng - li ni y khng ch nh ngha cu

trc li ni m cn xc nh hnh ng lin quan n li ni . C nhiu ngn ng

truyn thng a agent c a ra trong hai ngn ng truyn thng c s dng

rng ri nht nht l KQML ([11]) v FIPA-ACL ([10]).

KQML (Knowledge Query and Manipulation Language)

y l mt ngn ng c pht trin theo d n DARPA trong khong thi gian

u nhng nm 1990 [11]. KQML nh ngha ngn ng v giao thc cho qu trnh

chuyn i thng tin v tri thc trong h a agent.

KQML nh ngha ba mc l mc ni dung, mc thng ip v mc truyn

thng. Mi thng ip KQML nh ngha mt hnh ng thoi, ng ngha i km

hnh ng thoi , giao thc v mt tp cc thuc tnh. Cu trc chung ca mt

thng ip KQML nh sau

(performative-name

: sender A: receiver B: content X: language L: ontology N: reply-with W: in-reply-to P)

Mi mt thng ip KQML tng ng vi mt dng tng tc trong trng

performative-name. C ti 25 dng tng tc (performative) c nh ngha

bao gm ask-one, advertise, broadcast, insert... ng thi, KQML cho php m rng

v nh ngha thm cc dng tng tc khc khi cn thit.

Trng content m t ni dung ca thng ip. Ni dung ny c th rt phc

tp tu thuc vo nhu cu trao i thng tin ca hai agent trong phin lin lc .

Agent nhn s hiu c ni dung trong trng content bng cch tham chiu vo

trng ontology ca thng ip m n nhn c. KQML cng nh ngha cc


33/192


giao thc truyn thng bao gm c th t cc thng ip, cc perormative. V d

mt giao thc truyn thng c nh ngha trong KQML nh Hnh 2.1:

Hnh 2.1: Mt giao thc truyn thng trong KQML

FIPA-ACL (Foudation for Intelligent Physical Agent)

FIPA-ACL (Foundation Intelligent Physical Agent) l ngn ng truyn thngagent c pht trin nm 1997. FIPA-ACL cng da trn l thuyt hnh ng -

li ni v c cu trc tng t nh KQML. FIPA-ACL s dng XML theo dng

nh sau [10]:

So vi KQML, FIPA-ACL linh ng hn v c th d dng thm vo cc dng

tng tc mi. Tuy nhin, FIPA-ACL khng nh ngha cc performative theo kiu

s dng thnh phn trung gian (facilitator) nh trong KQML. l cc

performative nh brokerhay advertise.

2.1.2 Cc m hnh tng tc

Phn loi m hnh tng tcDa vo mc ch ca cc bn tham gia tng tc, c th chia cc hnh thc tng tc

thnh hai loi chnh: Hp tc v cnh tranh ([20]).

Hp tc: Hai bn cng thc hin mt cng vic chung (cng tc) hoc cng vic ca

bn ny l bc tin cho bn kia (Phi hp). Hnh thc tng tc ny thng xut

tell(X)

F

A B

broker(ask(X))tell(X)

advertise(ask(X))

ask(X)


34/192


hin khi cc agent c chung mc ch, nhim v hoc cng thc hin mt tin trnh

phc tp nht nh.

Cnh tranh: Hai bn cnh tranh nhau v thng tin, hoc quyn li (thng lng)

hoc hon ton tri ngc nhau v li ch (i u).Nh vy, c th c cc loi hnh tng tc nh sau:

Phn 2.3.2 s trnh by mt s m hnh tng tc theo cch phn loi ny.

Mt s m hnh hp tc

Cc giao thc phi hpTrong cc mi trng phn tn v hn ch v ti nguyn cho cc agent th cc

agent thng phi phi hp vi nhau. Nh trnh by trong phn 2.2.1, m hnh

tng tc c coi l phi hp khi cng vic ca agent ny l tin cho cng vic

ca agent kia.

cc agent phi hp vi nhau, cc nghin cu cho rng cn xy dng k

thut phn tn cng vic cn thc hin, bao gm c phn tn v iu khin

(control) v phn tn d liu (data). Phn tn v iu khin tc l cc agent c th

t ch trong vic sinh ra cc hnh ng mi v quyt nh mc ch k tip hng ti vic thc hin cng vic chung. Tri thc ca h thng trong trng hp

ny cn c bit bi tt c cc thnh phn trong h thng. Da trn tri thc ny,

cc agent s xc nh hnh ng tip theo cn thc hin trong mt chui cng vic

cn thit hon thnh mc tiu chung ca h thng.

Tng tc

Hp tc Cnh tranh

Phi hp Cng tc Thng lng i u

Hnh 2.2: Cc loi hnh tng tc


35/192


Lin quan n m hnh phi hp cn nhiu vn khc nh s tho thun

(commitment), cc quy c (conventions) v vic biu din cc tho thun hay cc

quy c ny ([20])

Cc giao thc cng tcChin lc chung ca cc giao thc cng tc l phn r nhim v cn thc hin ca

c h thng v sau phn tn cc tc v (task) c th cho cc thnh vin. Cc

agent cng hng ti ch chung thng qua vic thc hin cc tc v m mnh

c giao.

Vic phn r cc task nh th no c thc hin bi ngi thit k h

thng v tun theo cc giao thc c th. Cc tc v c phn r phi tho mn cc

yu cu sau:

- Trnh xung t ti nguyn- Cc tc v phi ph hp vi kh nng ca agent

- To ra mt agent c nhim v phn phi tc v cho cc agent khc trong h

thng.

- Xc nh cc tc v c c lp cao gim thiu vic truyn thng v

ng b ho kt qu.

- nh ngha li cc tc v nu cn thit hon thnh mt tc v khn cp.

Phn tip theo s trnh by hai giao thc cng tc tiu biu l giao thc mng hpng v giao thc bng en.

Giao thc Mng hp ng

Giao thc mng hp ng l mt giao thc tng tc kiu cng tc. Giao thc ny

s kt hp cc kt qu t cc agent khc nhau thng qua vic m hnh ho h thng

theo c ch hp ng s dng trong thng mi trao i sn phm v dch v.

Mng hp ng s cung cp gii php cho bi ton: tm mt agent ph hp cho mt

tc v cho trc. Gi s c mt agent c mt tc v cn x l. Agent ny s c

gi l manager, v agent c kh nng x l tc v ny gi l contractor. Tng tcgia manager v contractor s din ra theo biu tng tc sau:


36/192


Managers gi thng bo v tc v cn thc hin cho tt c cc agent khc trong h

thng. Khi nhn c yu cu, cc agent s gi tr li cho managerthng bo v

kh nng thc hin tc v ca mnh.Managers nh gi v chn ra agent ph hp

nht thc hin tc v v xc nhn agent thnh contractor. Contractors c

nhim v thc hin tc v v tr li kt qu cho manager.

Trn l thuyt, managerc th l bt k agent no trong h thng khi c

task cn thc hin. V vy mi agent c th nhn c nhiu task, nu agent l

agent c kh nng x l cao th rt nhiu managers chn agent lm contractor.Khi , contractors la chn task hp dn nht v m hnh mng hp ng s tr

nn phc tp hn nhiu.

Giao thc Bng en

Phng php gii quyt bi ton da trn giao thc Bng en c m t nh sau:

Gi s c mt nhm chuyn gia hoc agent cng ngi cnh mt bng en ln. Cc

chuyn gia s cng tc vi nhau gii quyt bi ton thng qua vic s dng bng

en pht trin li gii. Qu trnh gii bi ton bt u khi bi ton v d liu

u vo c vit ln bng en. Cc chuyn gia s quan st bng en v c gng

a ra kin pht trin li gii ca bi ton. Khi tm ra c mt thng tin/

kin ph hp, chuyn gia ny s vit kin (thng tin) ln bng en. Cc chuyn

gia khc s s dng thng tin ny tip tc tm ra li gii. Qu trnh c tip tc

nh vy cho n khi bi ton c gii quyt hon ton.

Hnh 2.3: Giao thc mng hp ng

Manager Contractor

Thng bo tc v cn thc hin

Phn hi nh gi kh nng thc hintask

Xc nhn mt hp ng cho contractor ph hp

Thc hin tc v v tr li kt qu

Kt thc tc v


37/192


p dng giao thc bng en cho h a agent ta s c m hnh tng tc kiu bng

en. Khi , h thng ny c cc c im sau:

- Tnh c lp v gii php: Cc chuyn gia c th a ra cc kin c lp vi

nhau.- Tnh a dng trong k thut gii bi ton: Thng qua bng en v cc phng php

biu din tri thc th mt bi ton c th c rt nhiu hng gii quyt khc nhau.

- Cho php biu din thng tin mt cch linh hot trn bng en.

- S dng ngn ng tng tc chung.

Mt giao thc kt hp cng tc v cnh tranh l thng lng s c trnh by chi tit

trong phn 3.2 v 3.3 ca ti liu. Phn tip theo dnh trnh by kin trc agent trung

gian.

2.1.3 Tng tc vi agent trung gian

2.1.3.1 Vai tr ca agent trung gian

Trn quan im ch trng n cc m hnh c s dng agent trung gian, ta c th chia cc

m hnh tng tc trong h a agent thnh: (i) tng tc vi agent trung gian v (ii)

tng tc khng s dng agent trung gian.

Cc m hnh tng tc khng s dng agent trung gian nh m hnh bng en,

mng hp ng c u im l n gin, d xy dng v ph hp vi nhng h thng a

agent ng. Cc m hnh ny yu cu cc agent phi bit c kh nng ca cc agentkhc trong h thng m n mun tng tc. Do , h thng vi cc m hnh ny kh m

rng cho agent khc tham gia nh trong mi trng Internet.

Khc vi cc m hnh bng en hay hp ng, m hnh tng tc vi agent trung

gian ([24], [35], [40]) s dng mt agent trung gianMidAgentnhm qun l kh nng ca

cc agent khc. Trong m hnh ny, Agent Yu cu (Requester Agent) s tng tc vi

MidAgent bit c kh nng ca cc agent (Agent Cung cp: Provider Agent) trong

h thng c th gii quyt c yu cu ca mnh . Vai tr caMidAgenttrong nhng m

hnh c th c th khc nhau nhng lp agent ny u c chung nhng c trng sau: Cung cp cc phng tin dch v c bn qun l x hi cc agent;

Phi hp cc dch v c cung cp theo mt giao thc xc nh no ;

m bo qun l cc agent bn trong x hi agent v qun l vic thm hay bt cc

agent tham gia vo h thng.


38/192


Trong [24], lp m hnh tng tc s dng agent trung gian c chia ra thnh 3 m hnh

nh gm m hnh tng tc kiu Agent Trung tm (Mediator Agent), m hnh tng tc

kiuMi gii (MatchMaker) v m hnh tng tc kiuiu phi (Broker).

2.1.3.2 Cc m hnh tng tc vi agent trung gianM hnh tng tc vi Agent Trung tm (Mediator Agent)

Trong m hnh ny, nhim v caAgent Trung tm l ch ng lin lc vi cc agent khc

c d liu hay tri thc cn thit trong h thng. Cc dch v m Agent Trung tm c th

cung cp l:

T ng xc nh cc dch v thng tin;

Xc nh vai tr ca cc agent trong h thng;

T thu thp v to ra thng tin t ccAgent Cung cp (Provider Agent) sau gi tr licho cc agent yu cu.

thc hin nhim v trn, Agent Trung tm s dng m hnh thng tin ton cc bng

cch thu thp v tch hp cc thng tin cn thit gii quyt cc yu cu hoc c th

chuyn yu cu cho cc agent ph hp trong h thng gii quyt. Nh vy, Agent Trung

tm ng vai tr va l agent trc tip qun l cc agent khc li va t tm ra thng tin cn

thit gii quyt v gi tr li kt qu cho cc agent yu cu. Cng vic caAgent Trung

tm l rt nhiu v hiu qu hot ng ca h thng ph thuc hon ton vo kh nng ca

agent ny. Vai tr caMidAgents gim i trong hai m hnh cn li c trnh by sau.

M hnh tng tc vi Agent iu phi (Broker Agent)

Trong m hnh ny, MidAgentng vai tr l Agent iu phi(Broker Agent). Cng vic

mAgent iu phi cn thc hin l mt phn cng vic ca Agent Trung tm v c biu

din nh trong Hnh 2.4. Khi c mt agent mi tham gia vo h thng, th n phi ng k

kh nng cung cp dch v ca mnh cho Agent iu phi. Dch v, tn v a ch ca

Agent Cung cp ny s c cp nht vo c s tri thc caAgent iu phi.


39/192


Khi c mt agent Agent Yu cu gi cho Agent iu phi mt yu cu dch v no ,Agent iu phi stm kim trong c s tri thc ca mnh xem cAgent Cung cp no c

th gii quyt c yu cu caAgent Yu cu khng v sau lin lc trc tip vi agent

gii quyt yu cu. Sau cng, Agent iu phi s gi li kt qu cho Agent Yu cu

v kt thc qu trnh tng tc.

Nh vy, trong m hnh tng tc ny, bt c mt lin lc no gia Agent Yu cu v

Agent Cung cp u phi thng qua Agent iu phi. Trong mt s ti liu, Agent iu

phi cn c gi l Facilitator ([40]). u im ca m hnh ny l kh nng m rng h

thng. Mt agent mi mun tham gia vo h thng th agent ch cn ng k dch v viAgent iu phi. Tuy nhin, nhc im ca m hnh ny l Agent yu cu phi gi i ton

b yu cu ca mnh choAgent iu phi m iu ny thng khng thc t c bit trong

thng mi in t.

M hnh tng tc vi Agent Mi gii (MatchMaker Agent)

Trong m hnh ny,MidAgentng vai tr nh mtAgent Mi gii m nhim v chnh ca

n l to ra c ch lin lc trc tip gia Agent Yu cu vAgent Cung cp nh minh ho

trong Hnh 2.5.

0: ng k,hu ng kdch v

4: Chuyn kt qu dch v

3: Yu cu dch v v giao tc

5: Tr li kt qu dch v

1: Yu cu dch vAgent Yu

cuAgent

iu phi

AgentCung cp

Hnh2.4: M hnh tng tc s dng Agent iu phi


40/192


Tng t nh m hnh Agent iu phi, khi mun tham gia vo h thng, mi agent phi

ng k dch v vi Agent Mi gii v tr thnh nh cung cp dch v (Agent Cung cp).Agent Mi gii s cp nht vo c s tri thc ca n tn v kh nng dch v ca Agent

Cung cp. Trong mt tng tc c th, khi c mt Agent Yu cu yu cu mt dch v, n

s gi yu cu nAgent Mi gii.Agent Mi gii s xem xt trong c s tri thc ca n

tm raAgent Cung cp c th thc hin yu cu v s gi cho Agent Yu cu tn, a ch

caAgent Cung cp . Qu trnh tng tc sau s din ra trc tip gia Agent Yu cu

vAgent Cung cp.

Nh vy, cng vic m Agent Mi gii phi thc hin l mt phn cng vic ca

Agent iu phi. Trong m hnh ny, Agent Yu cu ch cn gi i yu cu no lin quan

n vic tm raAgent Cung cp ph hp.

2.2 Thng lng trong h a agent

Khc vi cc m hnh tng tc kiu cng tc nh mng hp ng hay bng en, thng

lng l mt tin trnh tng tc va cng tc va cnh tranh c din ra gia hai hay

nhiu bn tham gia, bt u bng nhng mc tiu (ch) khc nhau, dn dn i n mt

tho thun chung c li cho tt c cc bn.

Trong bi ton thng lng, tu vo s bn tham gia, ngi ta chia lm bn nhm

l: thng lng 1-1, thng lng 1- n, thng lng n-1 v thng lng n-n. S phnchia ny c minh ho nh Hnh 2.6.

4:Tr li kt qu dch v

0: ng k,Hu ng kdch v

3: Yu cudch v

2:Tr li tn agent cung cp

1: Yu cu dch vAgent

Yu cuAgentMi gii

AgentCung cp

Hnh2.5: M hnh tng tc s dng Agent Mi gii


41/192


Thng lng 1-1: cn gi l thng lng song phng, ch c mt ngi bn

thng lng vi mt ngi mua. Thng lng n-1: nhiu ngi mua mt ngi bn. y chnh l hnh thc u gi

(Auction). u gi l mt trong nhng hnh thc mua bn ph bin trong thng

mi. Trong m hnh u gi (nhiu ngi mua, mt ngi bn), ngi mua s tr

gi theo mt cch thc no , v d nh ai tr gi cao nht s thng.

Thng lng 1-n: Mt ngi mua c th thng lng ng thi vi nhiu ngi

bn. Hnh thc ny cn gi l u gi ngc (Reverse-Auction).

Thng lng n-n: cn gi l thng lng a phng hay ch (market). Mi

ngi mua c th thng lng ng thi vi nhiu ngi bn v mi ngi bn

cng c th thng lng ng thi vi nhiu ngi mua.

Khi h thng c cc agent i din cho ngi mua v ngi bn th cc agent ny s t

ng thng lng vi nhau. Trong thng lng song phng ngi ta chia ra ba cch

tip cn [5]:

Cch tip cn da trn l thuyt tr chi

y l cch tip cn s dng chin lc tng tc gia cc agent ch k (self-

interested agent) theo cc lut tr chi. Trong cch tip cn ny, cc nh nghincu c gng xc nh mt chin lc ti u bng cch phn tch mi tng tc gia

cc agent ging nh trong mt tr chi v tm ra im cn bng ca qu trnh

tng tc gia cc agent .

Cch tip cn da trn Heuristic

1-1 1-n

n-1 n-n

S ngi mua

Sngibn

Hnh 2.6: Cc dng thng lng


42/192


43/192


Lt ct ca tp m

nh ngha 2.2 ([26]): Gi A l mt tp m trong mt tp khng rng X vi hm thuc

A . Mt lt ct ca tp m A c xc nh l tp cc phn t Xx sao cho

)(xA .

Hnh 2.8 minh ho mt cch xc nh lt ct ca mt tp m.

Cc ton t m

nh ngha 2.3 ([26]): Mt hm ]1,0[]1,0[]1,0[: G c gi l hm u tin nu n

tho mn bn iu kin.

1. ),(),( 21 auGauG nu 21 uu ,2. ),(),( 21 auGauG nu 21 aa ,3. G(1, a) = a,4. G(0, a) = 1.

nh ngha 2.4 ([25]): Mt hm ]1,0[]1,0[]1,0[: O c gi l hm ng nht u

tin nu n tho mn cc iu kin.

1. ),(),( 21 uOuO nu 21 uu ,2. ),(),( 21 uOuO nu 21 ,

Hnh 2.7: Cc phng php c lng m: hnh thang v tam gic

Hnh 2.8: Xc nh lt ct ca tp m


44/192


45/192


Max: trong trng hp Tw )0,...0,1(* = th

Max(a1,an) = max{a1,an}.

Min: trong trng hp Tw )1,...0,0(* = th

Min(a1,an) = min{a1,an}.

Average: trong trng hp TAnnn

w )1

,...,1

,1

(= th

n

aaaaF nnA

++=

...),...( 11 .

Mt ng dng quan trng ca ton t OWA l trong kt hp theo cc lng t

ngn ng[12]. Gi s

{A1, A2, ... An}

l mt tp cc tiu ch nh gi mt lp cc i tng no v x l mt i tng

thuc lp sao cho vi mi tiu chAi, gi tr hm ]1,0[)( xAi ch ra tho mn ca

i tng x i vi thuc tnh Ai. Nu mun tm mc tho mn tt c cc tiu ch

ca i tng x, k hiu lD(x), th

D(x) =Min{A1(x), A2(x), ... An(x)}

Nu mun tm mc tho mn t nht mt tiu ch ca i tngx, k hiu lE(x), th

E(x) =Max{A1(x), A2(x), ... An(x)}

Trong cc trng hp cn li, tu theo lng t ngn ng m phi xy dng cc

hm tm mc tho mn ca i tng x theo dng cc lng t n iu khng gim

hoc lng t n iu khng tng (xem chi tit [12]).

2.3.2 Chin lc thng lng cho agent bn

Trong m hnh thng lng song phng, agent bn c nhim v qun l vic giao dchng thi vi cc khch hng ca mnh. Mi agent bn c trang b mt tp cc tri thc

sau y:

a. Tp O = {O1, O2, ... Om} cc n v hng ho c th cung cp, mi n v hng ho

Oi (ca cng mt mt hng - mi agent bn ch bn mt mt hng) c m t thng


46/192


qua n thuc tnh { inii ooo ,..., 21 } v c mt gi tr li chgi nu bn c n v hng

.

b. Mt tpR = {r1, r2, ...rm} cc rng buc i vi ngi mua ca cc n v hng ho.

Tp ny c min gi tr kiu boolean (c hoc khng).

c. Mt tp C= {c1, c2, ...cn} cc hnh thc khuyn mi cho cc n v hng ho tng

ng, tp ny cng c min gi tr kiu boolean.

d. Mt tpB = {B1, B2, ... Bk} cc khch hng ang thng lng vi agent bn. Mi

khch hng c biu din qua cc thng tin sau: Tp cc n v hng ho b t

chi, n v hng ho va mi gii thiu i, cc thuc tnh v gi tr cc thuc tnh

yu cu.

Khi , hot ng thng lng ca agent bn din ra theo s c m t trong Hnh2.9.

Khi u: sau khi ng k vi h thng, agent bn s chuyn ngay vo trng thi ch

ch cc kt ni n t cc agent mua.

Ch: ti y, agent bn s ch i cc kt ni n t cc agent mua. Tu thuc vo ni

dung thng ip nhn c m agent bn chuyn vo cc trng thi ph hp.

Tm kim: l trng thi m agent bn chuyn vo khi nhn c thng ip find. Ti

y, n cp nht thm yu cu ca khch hng va nhn c v tin hnh tm kimcc n v hng ho tho mn cc yu cu m n nhn c. Nu khng tm c

n v hng no, n s gi i thng ip relax vi mong mun agent bn s nhng

b trn thuc tnh no . Nu tm thy, n chn n v hng ho no em li gi tr li

ch gi cao nht gii thiu vi agent mua km theo thng ip check. ng thi cp

nht n v hng ho mi nht va c gi i cho khch hng tng ng.


47/192


Tm li: l trng thi agent bn chuyn vo khi nhn c thng ip refind. Khi , n

s tin hnh tm kim theo cc yu cu c do khng c yu cu mi b sung. Nu tm

thy cc n v hng ho mi, agent bn s chn n v hng no cho gi tr li ch g i

cao nht gi n agent mua vi thng ip check. ng thi cp nht n v hng

ho mi nht va c gii thiu. Nu khng tm thy hng ho mi, agent bn chuyn

vo trng thi khuyn mi xem c th b sung cc hnh thc khuyn mi hay khng.

Khuyn mi: ti y, agent bn ly li n v hng ho mi nht c gii thiu cho

agent mua kim tra xem n v hng c hnh thc khuyn mi no khng. Vic

ny lun m bo c n v hng gii thiu, v trng thi ny ch c chuyn nsau trng thi tm li, trng thi tm li ch xy ra khi agent bn nhn c thng ip

refind, tc l trc agent mua nhn c mt n v hng ho do chnh agent

bn ny gii thiu. Nu n v hng ny c km theo khuyn mi, agent bn s gi cc

hnh thc khuyn mi ny km theo thng ip recheck. Nu n v hng ny khng c

khuyn mi hoc c khuyn mi nhng c gii thiu trc , agent bn s gi

thng ip relax , ng thi cp nht n v hng ho ny vo tp cc hng ho b

t chi.

Kt thc: l trng thi kt thc cho mt phin thng lng vi agent mua m khng

phi kt thc cho bn thn agent bn. Trng thi ny t c khi n nhn c thng

ip deal bo chp nhn hoc fail bo tht bi t pha agent mua.

Qu trnh trn c th din ra nhiu ln vi mt hoc nhiu agent mua khc nhau. Khc vi

agent mua l s kt thc nhim v sau khi thng lng, agent bn ch kt thc nhim v

khi bn ht cc mt hng m n qun l.

Hnh 2.9: M hnh chin lc thng lng ca agent bn


48/192


2.3.3 Chin lc thng lng cho agent mua

Trong m hnh thng lng song phng, mi agent mua i din cho mt khch hng,

s thng lng vi mt i tc duy nht v do mi agent mua c trang b cc tri

thc sau:a. TpA = {A1, A2, ... An} cc thuc tnh ca hng ho. Trong trng hp nhiu mt

hng th mi mt hng s c xem xt vi tp thuc tnh ring ca mt hng .

Mi thuc tnhAi c u tin ui tng ng. Trong trng hp thuc tnh Ai c gi

tr khong th mi gi tr (hoc khong con cc gi tr) trong khong c mt mc

tho mn ngi dng jia .

b. Mi thuc tnhAi c mt gi tr i gi l ngng nhng b ca thuc tnh. Gi tr

ca ngng ny cho bit thuc tnh tng ng c th c nhng b thm nu gitr tho mn jia ca n cha thp hn i.

c. Mt gi tr c gi l ngng chp nhn, c trng cho kh nng chp nhn ca

ngi dng. Nu kh nng chp nhn ca ngi dng cng cao th ngng chp

nhn c gi tr cng thp. Ngha l mt hng ch c chp nhn nu tho mn

tng th ca n khng nh hn ngng ny. Ngng chp nhn c c lng

t cc quan trng ui v ngng nhng b i ca mi thuc tnh nh sau:

c lng ngng chp nhn trn mi thuc tnh ),(iii uO = . Hm O

c chn tho mn cc iu kin ca nh ngha 3.4.

Kt hp cc gi tr i li vi nhau bng ton t OWA. Nhn xt rng, vi

yu cu ca ngi dng th nu c t nht mt thuc tnh khng tho mn th mt

hng s khng c chp nhn, ngha l trng hp ny thuc dng t nht mt

v dng ton t OWA c p dng l ton tMax.

),...,( 21 nMax = .

d. Mt tpD cc cp thuc tnh v gi tr ca cc thuc tnh gi i cho bn agentbn. Ti thi im u, agent mua ch gi i cc yu cu ca cc thuc tnh c u

tin cao nht. Sau , trong sut qu trnh thng lng, agent mua s gi thm yu

cu ch khi gi tr thuc tnh tng ng khng tho mn yu cu ca n. Do vy, khi

c yu cu nhng b t pha agent bn, agent mua ch tin hnh chn la kh nng

nhng b trn cc thuc tnh c yu cu lu trong tpD ny.


49/192


Vi tp cc tri thc ny, qu trnh thng lng ca agent mua din ra theo s c

minh ho trong Hnh 2.10.

Khi u: Trong trng thi khi u ca phin thng lng ny, agent mua tm ra

thuc tnh c u tin ui cao nht gi i. Trong trng hp c nhiu thuc tnh c

u tin uicao nht, n s gi i ton b cc thuc tnh ny.

Yu cu: Khi mun gi i yu cu v thuc tnh mi hoc gi tr mi cho thuc tnh

yu cu, agent mua s chuyn vo trng thi yu cu thc hin vic gi cc yu

cu cho pha i tc. ng thi vi vic gi yu cu i, agent mua cn phi cp

nht li ni dung cc thuc tnh c gi i (tp D) trong b nh hot ng ca mnh.

Ch: L trng thi agent mua ch i mt thng ip phc p t pha i tc. Khi

nhn c thng ip phc p, tu thuc vo ni dung ca thng ip m agent mua

chuyn vo cc trng thi tng ng.

Kim tra: Khi nhn c thng ip kiu check t pha agent bn th agent mua

chuyn vo trng thi kim tra. Ti y, n tin hnh kim tra xem c thuc tnh no b

vi phm hay khng. Mt thuc tnh b coi l vi phm nu gi tr ca n km hn gi tr

yu cu ca thuc tnh ang c lu gi trong b nh ng ca agent mua. Khi

nim km hn l tu thuc vo thuc tnh ca i tng. Chng hn, vi thuc tnh gi

phngth km hn l khi gi phngca khch sn nhn c cao hn gi c yu

cu.

Hnh 2.10: M hnh chin lc thng lng ca agent mua


50/192


Nu c t nht mt thuc tnh b vi phm, agent mua s chuyn sang trng thi

yu cu b sung cc yu cu mi. Trong trng hp ngc li, khng c thuc tnh

no b vi phm, n s chuyn vo trng thi chp nhn kim tra xem i tng c

th chp nhn c khng; bi v khi khng c thuc tnh no b vi phm th cha th

chc chn rng mt hng s c chp nhn bi ngi dng.

Chp nhn: Trong trng hp khng c thuc tnh no b vi phm sau trng thi kim

tra hoc nhn c thng ip recheck, agent mua s chuyn vo trng thi chp

nhn. Cc bc tin hnh tnh tho mn tng th ca i tng i vi ngi

dng, da trn cc k thut c lng m c tin hnh nh sau.

Tnh ph hp tng ng bi ca thuc tnh Ai da vo u tin ui v

ph hp ai: bi = G(ui,ai). Trong , ai c c lng m theo phng php hnh

thang t gi tr thc ca mt hng so vi cc gii hn ca ngi dng trn thuc tnh

tng ng. Hm G c chn tho mn cc iu kin ca nh ngha 2.3. Trong pdng c trnh by chng 5, hm chuyn i ph hp tng ng c

s dng l 1)1(),( += uaauG .

Ton t OWA c p dng tnh tho mn rng buc ca mt hng t

cc tho mn rng buc bi trn cc thuc tnh Ai. Nhn xt rng mt mt hng

mun tho mn c cc rng buc ca ngi dng th n phi tho mn cc rng

buc trn tt c cc thuc tnh; vy ton t OWA c p dng l dng tt c mi,

tc l ton t dng Min.

),...,(21

nbbbMin=

.

Tnh tho mn rng buc ca bn bn: bn bn c th c mt s rng

buc i vi ngi mua, chng hn v tui hay cm mang theo vt nui... Khi ,

tho mn c tnh l phn b (ph nh m) ca gi tr yu thch ca

khch hng v iu kin tng ng ( ia= vi ai l yu thch ca ngi dng,

]1,0[ia ).

V d: nu khch sn cm a sc vt vo phng m ngi dng mun a theo

sc vt vi mc l 40% (0.4) th tho mn rng buc 6.04.0 == .

Tnh tho mn khuyn mi : Vi mi hnh thc khuyn mi, tho mn

s bng yu thch ca khch hng i vi hnh thc khuyn mi ( ii a= vi ai

l yu thch ca ngi dng, ]1,0[ia ).


51/192


Nu c nhiu hn mt hnh thc khuyn mi cho cng mt mt hng, cc tho

mn i c kt hp vi nhau bi mt php ton i xng hai ngi (k hiu l )

tho mn iu kin:

1},max{ 2121

.Trong p dng chng 5, php ton c s dng l 212121 += .

Tnh kh nng chp nhn mt hng t cc gi tr tho mn yu cu ,

tho mn rng buc v tho mn khuyn mi : ),,( F= . Hm F

c chn tho mn cc iu kin ca nh ngha 2.6. Trong p dng chng 4,

hm tnh kh nng chp nhn ca ngi dng c s dng l

))1((),min(),,( +=F . Trong l ton t ng nht vi

phn t n v , tho mn cc iu kin ca nh ngha 2.5. Trong p dng

chng 4, ton t ng nht c p dng l

)1)(1()1(

)1(

baab

abba

+

=

.

vi l ngng chp nhn ca ngi dng.

Sau cc bc ny, nu kh nng chp nhn ln hn ngng chp nhn th mt

hng c chp nhn v agent mua gi thng ip deal n bn bn v chuyn vo

trng thi kt thc (thnh cng). Nu nh hn th mt hng khng c chp

nhn v agent mua s gi thng ip refind yu cu tm li vi cc yu cu c m

khng cn gi thm yu cu b sung.

Nhng b: Khi nhn c thng ip relax t agent bn th agent mua chuyn vo

trng thi ny. Ti y, n kim tra xem trong cc thuc tnh gi yu cu, c thuc

tnh no cn nhng b c na hay khng, mt thuc tnh c coi l cn nhng

b c nu gi tr hin ti ca n vn ln hn ngng nhng b ca thuc tnh

. Sau khi kim tra, nu khng c thuc tnh no c th nhng b thm, agent mua s

gi thng ip fail v chuyn sang trng thi kt thc(tht bi).

Ngc li, nu c thuc tnh cn c th nhng b thm, agent mua s chn ra

mt thuc tnh nhng b sao cho gi tr li ch ca mnh b gim i l nh nht. Gi

tr li ch b mt c c lng da trn tho mn b gim i ia v u tin ui

ca thuc tnh . Hm tnh gi tr li ch b mt c chn tho mn iu kin ca nh

ngha 3.4 v c th s dng hm uaauL =),( .

Khi , agent mua s tm xem thuc tnh Ai no cho gi tr li nh nht. Gi tr

thuc tnh y s c nhng b thm mt mc v agent mua chuyn sang trng thi


52/192


53/192

CHNG 3: ONTOLOGY TRONG H A AGENT 53

CHNG 3

ONTOLOGY TRONG H A AGENT

Khi nim ontology Biu din ontology

Phng php lun xy dng ontology

Ontology l mt thut ng trong trit hc nhm m t bn cht ca s tn ti v c

s dng rng ri trong lnh vc tr tu nhn to. Trong h a agent, ontology biu din

thng tin v tri thc v min quan tm ca cc agent nhm h tr tng tc. Mi ontologyl mt cu trc phn lp cc khi nim (concepts), cc thut ng (term) v cc mi quan

h (relations) gia cc khi nim, thut ng . Thng qua ontology, cc agent s hiu

c ni dung cc thng ip truyn thng m n nhn c trong qu trnh tng tc.

Ni dung chng

Luan Van Multi Agent

Documents

Transcript of Luan Van Multi Agent