Tìm kiếm ngữ nghĩa ứng dụng trên lĩnh vực edoc

1

LI CM N

u tin, chng em xin gi li cm n n Thy, C khoa Cng ngh Thng tin

trng i hc Khoa hc T nhin tn tnh dy d, du dt chng em sut bn nm

i hc.

Chng em cm n C Phm Th Bch Hu, ngi tn tnh hng dn, gip ,

ng vin chng em hon thnh lun vn ny.

Cui cng, chng con cm n Ba, M v nhng ngi thn khch l, h tr,

ng vin chng con trong thi gian hc tp, nghin cu c c thnh qu nh

ngy nay.

Thng 7 nm 2005

Sinh vin

Phm Th M Phng T Th Ngc Thanh

2

NHN XT CA GIO VIN HNG DN

....

Ngy thngnm 2005

K tn

ti: Tm kim ng ngh a ng d!ng trn l nh vc eDoc

0112274 Phm Th M Phng - 3 - 0112398 T Th Ngc Thanh

NHN XT CA GIO VIN PHN BIN

.

Ngy thngnm 2005

K tn



MC LC

M U.................................................................................................................................10 Chng 1 : TNG QUAN.....................................................................................................11

1.1. "t v#n ................................................................................................................ 11 1.2. Bi ton gii quyt ................................................................................................... 13 1.3. Hng tip cn......................................................................................................... 14

Chng 2 : C S L THUYT ........................................................................................17 2.1. Chin lc tm kim thng tin c$a cc b tm kim (Search Engine) ..................... 17

2.1.1. Mt s search engine thng d!ng: ................................................................... 17 2.1.2. Chin lc tm kim ........................................................................................ 32 Nguyn l hot ng........................................................................................................ 34

2.2. Semantic Web .......................................................................................................... 34 2.2.1. Khi nim......................................................................................................... 34 2.2.2. Kin trc .......................................................................................................... 36 2.2.3. Cc thch thc "t ra cho Semantic web ......................................................... 37 2.2.4. So snh web v web ng ngh a........................................................................ 41 2.2.5. Cc khi nim lin quan................................................................................... 42 2.2.6. Ontology .......................................................................................................... 44 2.2.7. Rdf ................................................................................................................... 46

2.3. eDoc ......................................................................................................................... 55 2.3.1. Tm hiu eLearning.......................................................................................... 55 2.3.2. Tm hiu eLib................................................................................................... 61 2.3.3. Tm hiu eDoc ................................................................................................. 68

2.4. Mt s v#n trong x% l ngn ng t nhin: ......................................................... 71 2.4.1. V#n trong vic x% l vn bn:...................................................................... 72 2.4.2. V#n x% l ng ngh a: ................................................................................... 72 2.4.3. Phn loi vn bn (Text Classification)........................................................... 82

Chng 3 : M HNH V GII THUT ..........................................................................84 3.1. Cng ngh tm kim ng ngh a trn th gii hin nay: ........................................... 84 3.2. Cc bc xy dng mt ng d!ng semantic search engine:.................................... 91

3.3.1. Xy dng kin trc Web ng ngh a:................................................................ 92 3.3.2. Lp ch& m!c ng ngh a tim tng: ................................................................... 93

3.3. M hnh ngh cho ng d!ng tm kim ng ngh a trn l nh vc eDoc................. 96 3.4. Cc gii thut s% d!ng ........................................................................................... 100

3.4.1. Gii thut x% l ti liu: ................................................................................. 100 3.4.2. Gii thut rt trch siu d liu: ..................................................................... 102 3.4.3. Gii thut phn loi l nh vc cho ti liu:...................................................... 104 3.4.4. Gii thut x% l cu truy v#n: ......................................................................... 104

Chng 4 : CHNG TRNH NG DNG....................................................................105 4.1. Gii thiu chng trnh ng d!ng: ........................................................................ 105 4.2. Kin trc c$a ng d!ng:......................................................................................... 105 4.3. M t phm vi ng d!ng........................................................................................ 107

4.3.1. M t bi ton: ............................................................................................... 107



4.3.2. Xc nh yu cu: .......................................................................................... 107 4.4. Xy dng ng d!ng: .............................................................................................. 108

4.4.1. Thit k d liu: ............................................................................................. 108 4.4.2. Thit k x% l:................................................................................................ 110

4.5. Kt qu chng trnh ............................................................................................. 112 4.6. Thc nghim chng trnh .................................................................................... 114

Chng 5 : KT LUN ......................................................................................................118 5.1. nh gi kt qu nghin cu ................................................................................. 118

5.1.1. 'u im ......................................................................................................... 118 5.1.2. Khuyt im:.................................................................................................. 119

5.2. Hng pht trin .................................................................................................... 119 TI LIU THAM KHO...................................................................................................120

I. Lun vn, lun n:...................................................................................................... 120 II. Sch, eBooks:............................................................................................................. 120 III. Website: ................................................................................................................. 122

PH LC..............................................................................................................................124 1. C php RDF: ............................................................................................................ 124 2. RDF Gateway: ........................................................................................................... 129

2.1. Kin trc c$a RDF Gateway:............................................................................. 130 2.2. Tnh nng (Features).......................................................................................... 132

3. H thng nhn ng ngh a:.......................................................................................... 138 3.1. Nhn ng ngh a c bn cho danh t: ................................................................. 139 3.2. Nhn ng ngh a c bn cho ng t: ................................................................. 141 3.3. Nhn ng ngh a c bn cho tnh t:................................................................... 142 3.4. H thng nhn ng ngh a LDOCE .................................................................... 142

4. H c s tri thc ng ngh a t vng WordNet .......................................................... 144 4.1. H thng nhn ng ngh a c$a danh t: .............................................................. 144 4.2. H thng nhn ng ngh a c$a ng t: .............................................................. 149



DANH MC CC BNG

Bng 1 : Bng hng dn nhanh v cch s dng mt s search engine ph bin ......... 28 Bng 2: S lc v cc c trng c a mt s search engine thng dng trn Internet .. 32 Bng 3 : Cc lp trong RDF ............................................................................................ 54 Bng 4:Cc thuc tnh c a RDF........................................................................................... 55 Bng 5: Danh sch cc ngh!a v rng buc c a cc t" th#c trong cu............................. 77 Bng 6 M t c s$ d% li&u cho 'ng dng.......................................................................... 110 Bng 7 Cc module c a chng trnh................................................................................ 110 Bng 8 Module eDocSearch ................................................................................................ 111 Bng 9 Module eDocSearch ................................................................................................ 111 Bng 10 Cc cu truy v(n th nghi&m............................................................................... 115 Bng 11 Thng k l!nh v#c khoa h)c my tnh................................................................. 116 Bng 12 Thng k l!nh v#c ngh& thu*t. ............................................................................. 116 Bng 13: Nhn ng% ngh!a c bn cho danh t".................................................................. 140 Bng 14: Nhn ng% ngh!a c bn cho ng t" .................................................................. 142 Bng 15 : Nhn ng% ngh!a c bn cho tnh t"................................................................... 142 Bng 16: H& thng nhn ng% ngh!a LDOCE .................................................................... 144 Bng 17:S# phn lp danh t" trong WordNet.................................................................. 148



DANH MC CC HNH

Hnh 1: Giao di&n c a Google............................................................................................... 18 Hnh 2: Giao di&n c a Yahoo................................................................................................ 19 Hnh 3: Giao di&n c a Ask Jeeves ........................................................................................ 20 Hnh 4: Giao di&n c a AllTheWeb ....................................................................................... 21 Hnh 5: Giao di&n c a Teoma ............................................................................................... 22 Hnh 6: Giao di&n HotBot ..................................................................................................... 23 Hnh 7: Giao di&n c a Altavista............................................................................................ 24 Hnh 8: Giao di&n c a Lycos................................................................................................. 25 Hnh 9: Kin trc t+ng c a Semantic web........................................................................... 36 Hnh 10: Mt Ontology n gin......................................................................................... 46 Hnh 11: M hnh d% li&u RDF............................................................................................. 51 Hnh 12 : Tiu chu,n nh gi tnh bo m*t c a eDoc ...................................................... 71 Hnh 13 Cc quan h& c php v rng buc ng% ngh!a ..................................................... 76 Hnh 14 Cy quyt -nh trong vi&c ch)n ngh!a ph hp. .................................................. 78 Hnh 15: Dng c s$ tm kim Web ................................................................................... 91 Hnh 16: M hnh ngh- cho 'ng dng tm kim ng% ngh!a trn l!nh v#c eDoc .......... 97 Hnh 17: Qui trnh x l c a t+ng search engine ................................................................ 99 Hnh 18: Gii thu*t x l ti li&u: ...................................................................................... 100 Hnh 19: Gii thu*t rt trch siu d% li&u.......................................................................... 103 Hnh 20: S . d% li&u quan h& c a 'ng dng.................................................................. 108 Hnh 21: Giao di&n chnh c a 'ng dng............................................................................ 112 Hnh 22: Giao di&n kt qu tm kim c a 'ng dng......................................................... 113 Hnh 23: Giao di&n qun l ti nguyn ............................................................................... 113 Hnh 24: Kin trc c a RDF Gateway............................................................................... 130 Hnh 25: Giao di&n c a RQF Query Analyzer. ................................................................. 136



DANH MC CC T/ VIT T0T

eDoc Electronic document

eLib Electronic library

eLearning Electronic learning

www World Wide Web

URI Uniform Resource Identifier

URL Uniform Resource Locator

HTTP Hypertext Transfer Protocol

RDF Resources Descriprion Framework

OIL Ontology Inference Language

OWL Ontology Web Language

XML eXtensible Markup Language



DANH MC CC THUT NG1

Class Lp

Property Thuc tnh

Metadata Siu d liu

Subject Ch$ , ch$ ng

Title Tiu

Namespace Khng gian tn

Predicate V ng

Triple B ba (subject, predicate, object)



M( )U

Hin nay, hu ht cc h thng tm kim trn Internet u i theo hng truyn

thng l tm kim theo t kho ( key word ). Theo cch tm kim ny, khi ta g vo

t cn tm, cc h thng tm kim s* hin th cc ti liu m trong n c cha t kho

cn tm. Do , kt qu tr ra l mt danh sch r#t nhiu cc ti liu, m c th cc ti

liu ny khng lin quan g n ni dung ta cn tm. V i khi cc h thng ny

khng a ra ht cc ti liu cn thit, tc l tha ti liu khng cn thit nhng li

thiu h+n nhng ti liu quan trng khc.

V#n "t ra l ta phi xy dng mt h thng tm kim nh th no khc

ph!c hin trng nu trn ?

gii quyt v#n ny, ta cn xy dng h thng tm kim sao cho p ng

y $ thng tin m ngi dng mong mun, ngh a l phi xy dng h thng tm

kim theo ng ngh a da trn thng tin ngi dng a vo.

T nhn thc trn chng em quyt nh chn ti: Tm kim ng% ngh!a 'ng

dng trn l!nh v#c eDoc (nhng ti liu in t% ting Anh) vi m!c ch tm hiu v

xy dng mt cng c! tm kim theo ng ngh a c th tm kim thng tin chnh xc

v y $, c th hn ch c phn no v#n tm kim theo t kho c$a cc

search engine hin ti.

Cc i tng nghin cu lin quan n ti: eDoc, Semantic Web, RDF,

OWL, Metadata,.

Trong phm vi ti, v thi gian thc hin ngn, nn chng em ch& th% nghim

chng trnh tm kim trong mt s l nh vc: Khoa hc my tnh (Computer Science),

Ngh thut (Art). Hai l nh vc ny c v, nh khng lin h vi nhau nhng thc t

vn c nhng trng hp cn phi phn bit, v d! nh ti liu v ngh thut lp

trnh (Art of programming) th phi phn ti liu v l nh vc khoa hc my tnh

ch khng phi ngh thut . Tm li, ng d!ng m chng em xy dng ch& tm kim

thng tin trong cc l nh vc nu trn. Tuy nhin, ng d!ng c th d- dng m rng ra

nhiu l nh vc cn li.



Chng 1 : TNG QUAN

1.1. t v(n

Nhu cu tm kim, nm bt thng tin l mt nhu cu khng th thiu trong i

sng c$a mi ngi. Khi vic s% d!ng World Wide Web tr nn ph. bin rng

khp, th cng vic c$a cc search engine c/ng tr thnh mt phn sng cn v c li

ch cho Web. Cc cng c! tm kim tr thnh nhng cng c! cng cng cho mi

ngi dng c$a Internet; Google v Yahoo, c/ng tr thnh nhng ci tn quen thuc.

Cc cng c! tm kim hin nay da trn mt trong hai dng c$a cng ngh tm

kim Web: tm kim do con ngi t ch& ng dn v tm kim t ng.

Cng c! tm kim do con ngi ch& ng dn s% d!ng mt c s d liu c$a

cc t kho, cc khi nim, v cc tham chiu. Nhng cng c! tm kim theo t kho

tr v mt dy cc trang, nhng phng php n gin ny thng dn n hng lot

cc kt qu khng lin quan v khng xc thc. Hot ng c$a mt cng c! tm kim

da trn ni dung l: s* m s lng cc t truy v#n ( cc t kho) so vi cc t hin

din trong mi trang c cha trong ch& m!c c$a n. Sau , cng c! tm kim ny s*

sp xp cc trang. Tip cn phc tp hn b0ng cch a cc v tr c$a t kho vo mt

mc quan trng c! th. V d!, cc t kho xu#t hin trong th, title c$a trang web th

quan trng hn trong phn body. Cc kiu khc c$a cng c! tm kim do ngi dng

ch& ng dn, nh Yahoo, s% d!ng cc lc 1 ch$ gip ch& hng tm kim v

tr v cc kt qu c lin quan hn. Nhng lc 1 ch$ ny do con ngi to ra.

Bi l do ny, chng ta phi tn chi ph to ra v duy tr trong cc t mang ngh a

thi gian (thay .i theo thi gian), v r1i th khng c cp nht thng xuyn nh

cc h thng t ng.

Cch tip cn tm theo t kho vn cn mt s hn ch, iu ny lm gim

i tnh ng n c$a cc search engine. V d! nh cc t 1ng m khc ngh a (ch+ng

hn: bank (ngn hng), bank (b sng), ) ho"c cc t c cc bin th khc nhau do

c cc tin t v hu t nh student v students; small, smaller, smallest; . Ngoi ra,

cc search engine khng tr v cc ti liu c cc t 1ng ngh a vi cc t trong cu



truy v#n m ngi dng nhp vo. Key word khng $ biu di-n chnh xc nhu

cu c$a ngi dng c/ng nh ni dung cc trang web, hn ch ny lm cho cc search

engine tr v nhng ti liu khng lin quan n v#n m ngi dng quan tm. Bi

v t*p hp cc t" kha l dng biu di-n s lc nh#t c$a ni dung, v do , cch

biu di-n ny l mt dng gc nhn lun l (logical view) c$a ni dung mang m'c

thng tin th(p nh(t, chnh l l do c bn khin cho cc Search Engine hin nay

c t2 l& s trang web h%u ch trn tng s trang web tr v th(p.

Google vi 400 triu ti liu thu v mi ngy v trn 8 t& trang web c lp ch&

m!c, v l cng c! tm kim thng d!ng nh#t c s% d!ng ngy nay, nhng thm ch

vi Google vn cn c nhiu v#n . V d!, b0ng cch no bn tm kim ch& vi mt

lng t d liu m bn cn trong mt bin kt qu khng lin quan c a ra?

Khi cng ngh tr tu nhn to (Artificial Intelligence_AI) pht trin mnh, th

v#n "t ra l lm th no a ra nhng phng php tm kim tt hn m c th

thc s tin cy vo nhng kt qu tm kim . l xu hng c$a nhng cng c! tm

kim da vo ng ngh a v cc agent tm kim theo ng ngh a. Mt cng c! tm kim

ng ngh a tm kim cc ti liu c ngh a tng t nhau ch khng ch& nhng t ng

tng t nhau. Web tr thnh mt mng ng ngh a, phi cung c#p nhiu siu d

liu v ni dung c$a n, thng qua vic s% d!ng cc th, RDF (Resource Description

Framework) v OWL (Ontology Web Language), cc th, ny s* gip thc hin a

Web vo trong mng ng ngh a. Trong mng ng ngh a, ngh a c$a ni dung c

th hin tt hn, v nhng lin kt logic c thc hin gia nhng thng tin lin quan

nhau.

Cng c! tm kim ng ngh a, chng ta cp y, c hai u im ln so vi

cc cng c! tm kim truyn thng:

1. N ch#p nhn cc truy v#n c pht biu ngn ng t nhin.

2. Kt qu l tm kim mt mu thng tin; khng phi l mt danh sch cc ti

liu c th (ho"c khng) cha thng tin yu cu.

Tht vy cng c! tm kim ng ngh a bt u vi lng thng tin qu ti. N

tip nhn mt s cc tc v! khng c ai a thch trong vic tm kim thng tin hin



nay: m ra mi ti liu c$a danh sch kt qu v qut n mt cch th$ cng l#y

thng tin. Theo cch , cc cng c! tm kim ng ngh a c kh nng cch mng ho,

hng n vic tm kim thng tin in t% mt cch t ng: n thay .i m hnh tm

kim t vic thu hi ti liu n vic tr li cu hi.

1.2. Bi ton gii quyt

Theo thng k trong nm 2001: Cc nhn vin tn trung bnh 8 gi mt tun,

hay 16% gi cng hng tun c$a h, tm kim v s% d!ng ni dung thng tin bn

ngoi. Chi ph lng ch& ring cho cng ty c$a M l 107 t& la mt nm. Vic tm

kim ng ngh a l mt c hi y ngh a cho cc cng ty gip cho nhn vin c$a h

c kh nng hn v hiu qu hn trong vic "t thng tin bn ngoi vo cng vic c$a

h. Khng cn ni nhiu thm na. S qu ti thng tin l mt v#n ln trong x

hi thng tin.

Nhng khm ph tng t c/ng c tm th#y trong nhiu nghin cu, lm n.i

bt v#n : phi a ra gii php trong vic ci tin x% l tm kim thng tin. Ngoi tr

nhng ch li to ln m cc cng c! tm kim mang li cho chng ta nhng nm gn

y b0ng vic lm cho c th truy cp n hng triu cc ti liu, b#t ch#p v tr vt l

v ngn ng, th chng vn c mt s hn ch c bn. V d!, chng khng hiu cc

t con ngi g vo v do t ti mt s lng kh.ng l1 c$a cc kt qu sai. Hn

na, chng hot ng hiu qu khi h2i v nhng s kin, ch+ng hn nh Kerry v

vua c$a Ty Ban Nha. Tuy nhin, chng thc hin nhiu kt qu khng tt nu cu

truy v#n ni v s lin h gia cc khi nim ch+ng hn nh Nhng quc gia no

tham gia trong chin tranh Iraq? v t.ng thng nc Php theo chnh ng no?

C ba v#n cn c ci tin ci thin cc kt qu c$a cng c! tm kim l:

(i) Cng c! tm kim cn cho php nhng truy v#n phc tp hn (v

d! trong ngn ng t nhin),

(ii) Cng c! tm kim cn hiu nhng g con ngi h2i, v

(iii) Cng c! tm kim phi cung c#p cu tr li cho truy v#n (c th

sao lu li nhng lin kt n cc ti liu m cho ra cu tr li).



1.3. Hng tip c*n

C hai tip cn ci thin cc kt qu tm kim thng qua phng php ng

ngh a:

1. Kin trc c$a Semantic Web.

2. Lp ch& m!c cho ng ngh a tim tng (Latent Semantic Indexing).

Tuy nhin, hu ht cc cng c! tm kim da trn ng ngh a phi chu nhng

v#n thc thi bi qui m c$a mng ng ngh a r#t ln. Nh0m m!c ch lm cho tm

kim ng ngh a tr nn hiu qu trong vic tm kim cc kt qu mong mun, mng

ny phi cha mt lng ln cc thng tin lin quan. Cng lc , mt mng rng ln

to ra nhng kh khn trong vic x% l nhiu ng dn c th c cho mt gii php

lin quan.

Chng ta s% d!ng kha cnh sc bn c$a cng ngh Web ng ngh a kt hp

ch"t ch* s phi hp c$a cc cng ngh tin tin lm cho m hnh c th chuyn

nhanh trong vic tm kim thng tin.

Cng ngh& x l ngn ng% t# nhin cho php ngi dng h2i nhng

cu h2i m h mun, hn l phi nu ln nhng t kho c lin quan

trong cu h2i c$a h.

Cc Ontology -nh ngh!a l!nh v#c quan tm. Chng c xem nh l

b no c$a cng c! tm kim, bi v n c gng hiu nhng cu truy

v#n c$a ngi dng trong cc t c$a ontology ny. Theo cch ny ch

r0ng cng c! tm kim ng ngh a c$a chng ta khng phi l c m!c

ch thng thng nh Google, m n c nh p d!ng i vi mt

l nh vc hay khu vc c! th (v d! v l nh vc php l, vn ho, th thao

v.v).

Phn tch tri th'c. Cng ngh ny chuyn d liu khng c c#u trc

sang thng tin c c#u trc. N rt trch thng tin t cc vn bn t do,



cc vn bn bn c#u trc v c#u trc pht sinh ra ontology vi tri thc

tht s.

Truy c*p tri th'c thng minh. Cc cu tr li cho cc truy v#n t

c do vic truy v#n ontology c a ra t ng, v c biu di-n

trong nhng dng khc nhau:

o D liu c$a thc th chnh c h2i n (v d! trong l nh vc

x hi, d liu c$a mt ngh s ).

o nh hng ng ngha. Nhng t c$a cc cu tr li c t

ng siu lin kt n cc khi nim ontology con, cho php nh

hng b0ng ngh a.

o Cc th thng minh v lin kt thng minh. Cc cu tr li lun

c sao lu bi cc ngu1n v cc ti liu chng da vo. Khi

nhng ti liu c tra cu, th phn mm gn th, v lin kt

s* t ng nhn ra cc t cha ngh a l nh vc v lin kt chng

n ontology, hay thm vo cc th, thng minh vi nhng hot

ng c nh ngh a trong ontology.

o S tng tng thng minh. Thng thng, cc cu tr li

pht sinh ra nhiu cc khi nim lin quan v cc mi quan h.

Phm mm tng tng thng minh cho php mt khi nim i

xuyn qua tri thc ny.

C mt v#n m cng c! tm kim ng ngh a c nh ngh a y vn cha

th hon t#t so vi nhng cng c! tm kim vi m!c ch thng thng (khng c ng

ngh a) nh Google l: phm vi. Trong Google bn c th tm kim vi b#t k3 t

kho no trong b#t k3 l nh vc no. Nu cc t kho xu#t hin trong mt s ti liu

trn Web, Google s* tm th#y n. Mt cng c! tm kim ng ngh a cn mt s tri thc

nng cao: n cn bit ngh a, c biu di-n trong mt ontology. Thc t l cc

ontology trong trng thi thi hnh hin ti vn cn lm b0ng th$ cng, hn ch

chng trong nhng m!c ch thng thng. Do , cc cng c! tm kim ng ngh a l

nhng cng c! quan trng cho nhng l nh vc c! th. Trong trng hp ny, m!c ch



c$a cc cng c! tm kim ng ngh a l b. sung cho cc cng c! tm kim thng

thng, hn l cnh tranh nh nhng i th$ .



Chng 2 : C S L THUYT

2.1. Chin lc tm kim thng tin c a cc b tm kim (Search Engine)

2.1.1. Mt s search engine thng dng:

Sau y l danh sch mt s search engine. Ti sao chng c xem l nhng

search engine ln? l bi v chng c bit n nhiu v s% d!ng tt. i vi

cc chuyn gia web, cc cng c! tm kim ln l danh sch nhng ni quan trng nh#t

bi chng pht sinh ra mt lng r#t ln cc trang web tim tng. i vi nhng

ngi tm kim, cc cng c! tm kim ph. bin thng tr ra cc kt qu ng tin cy

hn. Nhng search engine ny r#t c th c duy tr tt v nng c#p khi cn thit,

gi th cn b0ng vi tc pht trin c$a web.

Nhng search engine sau l t#t c nhng la chn tt nh#t bt u khi tm kim

thng tin:



2.1.1.1. Google: http://www.google.com/

Hnh 1: Giao di&n c a Google

Nguyn thu4, Google l mt n c$a trng i hc Stanford c thc hin

bi hai sinh vin Larry Page v Sergey Brin gi l BackRub. n nm 1998, th .i

tn thnh Google, v 1 n ny tr thnh cng ty ring Google "t ti khun vin

trng i hc. N vn cn c lu gi cho n ngy nay.

Google l cng c! tm kim n.i ting, tt nh#t trong cc la chn tm kim

thng tin trn web. Dch v! da vo crawler, spider cung c#p trang web vi thng tin

a ra ton din cng vi mc lin quan tt. y l cng c! tt nh#t hin nay trong

vic tm kim b#t c th g bn mun.

Tuy nhin, Google cung c#p chn la tm kim ch$ yu v cc trang web.

S% d!ng hp tm kim trn trang ch$ Google, bn c th d- dng nh v cc nh qua



web, nhng ngh c "t trong cc nhm tho lun Usenet, nh v thng tin tin

tc hay thc hin tm kim sn ph5m.

2.1.1.2. Yahoo: http://www.yahoo.com/

Hnh 2: Giao di&n c a Yahoo

a ra nm 1994, Yahoo l th m!c c/ nh#t c$a web, mt ni m cc nh

bin tp t. chc cc trang web trong cc danh m!c. Tuy nhin, vo thng 10 nm

2002, Yahoo chuyn sang lp danh sch da vo crawler cho nhng kt qu chnh c$a

n. Cng c! ny s% d!ng cng ngh t Google cho n thng 2 nm 2004. Hin nay,

Yahoo s% d!ng cng ngh tm kim ring c$a mnh.

Yahoo Directory vn t1n ti. Bn s* ch& ra cc lin kt danh m!c pha di

mt s cc trang web lit k trong kt qu tr v c$a mt tm kim t kho. Khi c



xu#t, nhng trang web ny dn bn n mt danh sch cc trang web c xem

xt v ph chu5n bi mt nh bin tp.

Cng ngh AltaVista v AllTheWeb c phi hp vi k thut Inktomi, mt

cng c! tm kim da trn crawler, to nn mt Yahoo crawler hin nay.

2.1.1.3. Ask Jeeves: http://www.askjeeves.com/

Hnh 3: Giao di&n c a Ask Jeeves

Ask Jeeves bt u n.i ting t nm 1998 v 1999, c bit nh l mt cng

c! tm kim ngn ng t nhin cho php ta tm kim b0ng cch h2i nhng cu h2i

v tr v kt qu vi nhng g c v l tr li ng v mi th.

Thc s, cng ngh khng phi l nhng g lm cho Ask Jeeves thc thi tt.

Bn cnh cc bi cnh, cng c! ny ti mt thi im c khong 100 trnh son tho



gim st cc log tm kim. Sau chng vo trong web v nh v nhng site m

chng cho l tt nh#t tng xng vi cc truy v#n ph. bin nh#t.

2.1.1.4. AllTheWeb: http://www.alltheweb.com/

Hnh 4: Giao di&n c a AllTheWeb

c Yahoo cung c#p ngu1n, c th th#y AllTheWeb l mt tm kim thun

tu (pure search) nh nhng hn, tu3 bin hn v d- chu hn l khi thc hin

Yahoo. Tiu im l trong tm kim web, ngoi tr tin tc, tm kim hnh nh, video,

MP3 v FPT c/ng c a ra.



2.1.1.5. Teoma: http://www.teoma.com/

Hnh 5: Giao di&n c a Teoma

Teoma l mt cng c! tm kim da trn crawler c s hu bi Ask Jeeves.

N c s lng trang web c ch& m!c nh2 hn Google v Yahoo. Nm 2000,

Teoma ra i cng vi thnh cng c$a mnh: a ra c nhng th lin quan. Tnh

nng Refine c$a cng c! ny xu#t ra nhng ch$ kho st sau khi bn thc

hin mt tm kim.

Teoma c Ask Jeeves mua vo thng 9 nm 2001 v c/ng cung c#p mt s

kt qu cho web site ny.



2.1.1.6. HotBot: http://www.hotbot.com/

Hnh 6: Giao di&n HotBot

HotBot h tr truy cp d- dng n 3 trang web search engine da vo crawler

ln: Yahoo, Google, v Teoma. Khng nh mt meta search engine, n khng th pha

trn cc kt qu t t#t c cc crawler ny vi nhau. Do , n l mt cch nhanh, d-

dng l#y cc kin tm kim web khc nhau trong mt ni.



2.1.1.7. AltaVista: http://www.altavista.com/

Hnh 7: Giao di&n c a Altavista

AltaVista c a ra vo thng 9 nm 1995 v c xem nh l Google

trong mt vi nm, n cung c#p nhng kt qu lin quan v c mt nhm ngi

dng yu thch cng c! tm kim ny. Nhng t sau nm 1998, ngi ta khng cn a

chung AltaVista na, bi v s mi m, c$a cc danh sch AltaVista v tin tc c

a ra c$a crawler trong trang web ny khng c cp nht thng xuyn.

Ngy nay, AltaVista mt ln na tp trung vo tm kim. Cc kt qu n t

Yahoo, v cho php n cc trang web tm hnh nh, MP3/Audio, Video, cc danh

sch danh m!c con ngi v cc kt qu tin tc. Nu mun mt cm gic nh nhng

hn Yahoo nhng vn c cc kt qu c$a Yahoo, AltaVista l mt chn la tt.



2.1.1.8. Lycos: http://www.lycos.com/

Hnh 8: Giao di&n c a Lycos

Lycos l mt trong nhng cng c! tm kim c/ nh#t trn web, c a ra nm

1994. c m t nh l nhng c.ng truy cp web ( web portal ) hay nhng trung tm

truy cp, l ni m ngi dng i vo l#y thng tin cho mi l nh vc, k c tn gu,

gi th in t%,



Search

Engine

Google AlltheWeb AltaVista Teoma

Database google.com alltheweb.com altavista.com teoma.com

Kch thc(#

trang )

Khong 8 t& (1

t& khng nh

ch& m!c trn

ton vn bn)

Khong 3 t&,

ch& m!c trn

ton vn bn.

Khong 1 t& Khong 1 t&

a phng

tin

(multimedia)

H tr H tr H tr Khng h tr

Ton t%

M"c nh AND AND AND AND

Loi tr - - - -

C!m t Dng d#u Dng d#u Dng d#u Dng d#u

Rt gn Khng h tr

Dng k t *

thay th

cho cc k t

trong d#u

Khng h tr Dng k t * Khng h tr

Boolean OR (ch& dng

cho danh t

ring )

AND, OR,

ANDNOT,

RANK, ()

AND, OR,

ANDNOT,

NEAR, ()

OR (ch& dng cho tn

ring)



Stop words Thng thng

b2 qua cc t

thng d!ng

+ nu mun

tm v phi "t

trong c"p d#u

Dng d#u

trong search

c bn

B2 qua trong

search nng

cao

Thng thng b2 qua

cc t thng d!ng

+ nu mun tm

Danh t

ring

Khng h tr Khng h tr H tr Khng h tr

Gii hn

field cn tm

intitle:

inurl:

allintitle:

Allinurl:

filetype:

Link:site:

Trong search

nng cao :

cache:info:

Normal.title:

url.all:

Link.all:

Link.extension

:

Title:

domain:

Link:

image:

Text:

url:

host:

Anchor:

applet:

intitle:

inurl:

site:

geoloc:

lang:

last:

afterfate:

Cc "c tnh

"c bit

~ tm t 1ng

ngh a

Gii hn bi

ngn ng

Nhiu kiu file

: pdf, doc,

Caches : trang

web khi nh

ch& m!c

Duyt qua cc

URL

Trong tm

nng cao :

gii hn bi

ngy, domain,

a ch& iP

Gii hn bi

ngy, v tr,

ngn ng

Trong tm

nng cao : s%

d!ng sortby

lc v sp xp

kt qu.

Dng refine ti u

kt qu.

Resource c c

cc trang v lin kt

tp trung trn ch$

cn tm.



'u im

'u im

chnh

R#t tt vi

nhng trang

c ph. bin

cao.

Cc trang tin

tc gn y

Tt nh

Google.

Khng c

stopword.

Dng nhiu

ton t%

Boolean trong

tm kim.

Trong tm

nng cao h

tr hin th kt

qu theo

ph. bin c$a

t.

Tnh ph. bin tt,

da vo s lng

trang web cng ch$

vi cc trang ang

xt. Thng t kt

qu ng khch l.

Search

Engine

Google AlltheWeb AltaVista Teoma

Bng 1 : Bng hng dn nhanh v cch s dng mt s search engine ph bin

Search

engine

C s$ d% li&u Ton t L#a ch)n tm

kim

Linh tinh

Google

http://www.g

oogle.com

H tr tm

kim nng

cao

H thng th

m!c ch$

(Subject

Ton vn bn

c$a cc trang

web, .pdf,

.doc, .xls, .ps,

.wpd

(4.3B, + 1B

mt phn c$a

ch& m!c

URLs)

AND (m"c

nh)

OR (danh t

ring)

+ cho cc stop

word thng

d!ng, cho cc

URL ho"c cc

trang c! th (v

Dng * rt

gn.

Dng tm c!m

t.

Fields : intitle:,

inurl:, link:, site:

Tm trn h

thng danh m!c

cc ch$ trong

Kim li chnh

t.

Lu tr cc trang

lp ch& m!c.

Tt cho tm cc

trang hay b li

404.

Phin dch n 5

ngn ng.



Directory)

H thng th

m!c m

(Open

Directory)

Tin tc : cp

nht thng

xuyn (4500

ngu1n ).

Cc dng file

nh

Nhm :

Usenet t

1981 n nay

d! +edu)

- loi tr

th m!c web.

Tm cc trang

web tng t.

~ tm t 1ng

ngh a.

AlltheWeb

http://allthew

eb.com

H tr tm

kim nng

cao

Ton b vn

bn cc trang

web, .pdf,

Flash,

(3.1B ton b

ch& m!c

URLs)

Tin tc : cp

nht thng

xuyn (3000

ngu1n)

Tranh nh

Video

Audio

FPT

AND (m"c

nh)

OR, phi "t

cc t trong

d#u .

ANDNOT,

RANK

- loi b2

Khng rt gn.

Dng d#u cho

c!m t.

Field intitle:inurl:

link:site:

Trong tm nng

cao :

gii hn theo

ngy, ngn ng,

domain, file

format, a ch&

iP.

Kim li chnh

t.

Tm nng cao :

tranh nh, video.

H tr s% d!ng

k thut

clusters ti

u cu truy v#n.

AltaVista

http://altavist

a.com

Ton b vn

bn cc trang

web (khong

AND (m"c

nh)

Trong tm nng

D#u * rt gn.

D#u cho c!m

t.

Kim li chnh

t.

Phin dch : 8



H tr tm

kim nng

cao

H thng th

m!c ch$

(Subject

Directory )

H thng th

m!c m

(Open

Directory)

1B) v file

.pdf.

Tin tc (3000

ngu1n), nh,

MP3/Audio,

Video.

cao ho"c danh

t ring trong

tm c bn :

AND, OR,

ANDNOT,

NEAR, d#u ()

l1ng nhau.

- cho loi tr.

Tm nng cao :

gii hn ngy,

ngn ng.

ngn ng c$a

Chu u & cc

ngn ng c$a

Chu .

AltaVistaPrima :

ti u cu h2i.

Teoma

http://teoma.c

om

H tr tm

kim nng

cao

Ton b vn

bn trang web

(khong 1B)

AND (m"c

nh)

OR (danh t

ring)

+ ho"c cho

stopword

- loi b2

Khng rt gn.

Dng d#u cho

c!m t.

Field intitle:inurl:

site:geoloc:lang:l

ast:

afterdate:befored

ate:

betweendate:

Trong tm nng

cao :

gii hn theo

ngy, ngn ng,

domain, file

format, a ch&

iP.

Kim li chnh

t.

Gom nhm kt

qu Refine ti

u cu h2i.

Resource c

cc trang ho"c

lin kt tp trung

vo ch$ .



AskJeeves

www.ask.co

m

Nhn kt qu

t CSDL c$a

Teoma.

Tm sn ph5m

:

PriceGrabber.

com,

Tm tranh nh

:

Picsearch.co

m

Tm tin tc :

Moreover.co

m.

Ging Teoma.

i vi nhng

cu h2i n

gin, xu#t hin

c%a s. i

thoi.

Ging Teoma.

Click vo

Remove Frame

th#y URLs

c$a cc trang.

Kim li chnh

t.

AskJeeves for

Kids

www.ajkids.c

om

Tr li tt cc

cu h2i n

gin.

Games cho

tr, em,

Tin tc theo

tng nhm

tu.i.

H2i b0ng ngn

ng t nhin.

Khng s% d!ng

cc ton t%

Boolean.

Click vo No

frames th#y

URL c$a trang

kt qu.

Dn n cc

trang ph!c v!

hc tp : t in,

vt l, khoa hc,

bn 1, lch

s%,

Yahoo

http://dir.yaho

o.com

Xem xt cc

trang web

(khong 13K)

AND (m"c

nh)

OR

C!m t :

Rt gn : *

Fields t: title,

u:URL

Nhiu dch v!

trong Yahoo:

Tin tc : tng

gi.

Th thao :t& s,..

Bn 1, thi tit,



mua sm.

Bng 2: S lc v cc c trng c a mt s search engine thng dng trn Internet

2.1.2. Chin lc tm kim

T search engine thng c s% d!ng rng ri m t cc cng c! tm

kim da trn crawler v cc th m!c do con ngi cung c#p. y l hai loi c$a cc

search engine tp hp cc danh sch c$a chng trong nhng cch khc nhau hon

ton.

Search engine da vo crawler g1m 3 phn:

B thu th*p thng tin Robot

Robot l mt chng trnh t ng duyt qua cc c#u trc siu lin kt thu

thp ti liu v mt cch quy n nhn v t#t c cc ti liu c lin kt vi ti liu

ny.

Robot c bit n di nhiu tn gi khc nhau : spider, web wanderer ho"c

web worm, crawler Nhng tn gi ny i khi gy nhm ln, nh t spider ,

wanderer lm ngi ta ngh r0ng robot t n di chuyn v t worm lm ngi ta

lin tng n virus. V bn ch#t robot ch& l mt chng trnh duyt v thu thp

thng tin t cc site theo ng giao thc web. Nhng trnh duyt thng thng khng

c xem l robot do thiu tnh ch$ ng, chng ch& duyt web khi c s tc ng c$a

con ngi.

B l*p ch3 mc Index

H thng lp ch& m!c hay cn gi l h thng phn tch v x% l d liu, thc

hin vic phn tch, trch chn nhng thng tin cn thit (thng l cc t n , t

ghp , c!m t quan trng) t nhng d liu m robot thu thp c v t. chc thnh



c s d liu ring c th tm kim trn mt cch nhanh chng, hiu qu. H

thng ch& m!c l danh sch cc t kho, ch& r cc t kho no xu#t hin trang no,

a ch& no.

B tm kim thng tin Search Engine

Search engine l c!m t dng ch& ton b h thng bao g1m b thu thp

thng tin, b lp ch& m!c v b tm kim thng tin. Cc b ny hot ng lin t!c t

lc khi ng h thng, chng ph! thuc ln nhau v m"t d liu nhng c lp vi

nhau v m"t hot ng.

Search engine tng tc vi user thng qua giao din web, c nhim v! tip

nhn v tr v nhng ti liu tho yu cu c$a user.

Ni nm na, tm kim t l tm kim cc trang m nhng t trong cu truy v#n

(query) xu#t hin nhiu nh#t, ngoi tr stopword (cc t qu thng d!ng nh mo t a,

an, the,). Mt t trong cu truy v#n cng xu#t hin nhiu trong mt trang th trang

cng c chn tr v cho ngi dng. V mt trang cha t#t c cc t trong cu

truy v#n th tt hn l mt trang khng cha mt ho"c mt s t. Ngy nay, hu ht

cc search engine u h tr chc nng tm c bn v nng cao, tm t n, t ghp,

c!m t, danh t ring, hay gii hn phm vi tm kim nh trn m!c, tiu , on

vn bn gii thiu v trang web,..

Ngoi chin lc tm chnh xc theo t kho, cc search engine cn c gng

hiu ngh a thc s c$a cu h2i thng qua nhng cu ch do ngi dng cung c#p.

iu ny c th hin qua chc nng s%a li chnh t, tm c nhng hnh thc bin

.i khc nhau c$a mt t. V d! : search engine s* tm nhng t nh speaker,

speaking, spoke khi ngi dng nhp vo t speak.



Nguyn l ho4t ng

Search engine iu khin robot i thu thp thng tin trn mng thng qua cc

siu lin kt ( hyperlink ). Khi robot pht hin ra mt site mi, n gi ti liu (web

page) v cho server chnh to c s d liu ch& m!c ph!c v! cho nhu cu tm kim

thng tin.

Bi v thng tin trn mng lun thay .i nn robot phi lin t!c cp nht cc

site c/. Mt cp nht ph! thuc vo tng h thng search engine. Khi search engine

nhn cu truy v#n t user, n s* tin hnh phn tch, tm trong c s d liu ch& m!c

v tr v nhng ti liu tho yu cu.

2.2. Semantic Web

2.2.1. Khi ni&m

Web ng ngh a l mt dng m rng c$a web hin nay, m cho php ta truy

tm, chia s,, phi hp, s% d!ng li v rt trch thng tin mt cch chnh xc, d- dng.(

Tim Berners Lee, XML 2000 ).

Web ng ngh a l mt mng li thng tin c lin kt theo cch m my tnh

c th d- dng x% l c trn quy m ton cu. Chng ta c th xem web ng ngh a

nh l mt c s d liu ton cu c lin kt vi nhau.

Web ng ngh a c pht trin bi Tim Berners Lee, nh pht minh c$a

WWW, URIs, HTTP, v HTML. Hin nay c mt nhm nghin cu ti tp on

WWW ang ci tin, m rng v tiu chu5n ho h thng ng ngh a.

D liu trong tp tin HTML thng hu ch trong mt s trng hp. Phn ln

d liu trn web l dng HTML nn kh s% d!ng trn quy m ln, bi v n khng c

mt h thng ton cu xu#t bn d liu.

Do , Web ng ngh a c xem nh l mt gii php k thut.

Web ng ngh a c xy dng ch$ yu trn c php s% d!ng URIs biu di-n

d liu, thng th#y l c#u trc da trn b ba (subject, predicate, object), v d!: nhiu

b ba c$a d liu URI c th c c#t gi trong c s d liu, ho"c thay th ln nhau



trn word wide web b0ng cch s% d!ng mt tp cc c php "c bit c php trin

chuyn bit ph!c v! cho nhim v! . C php ny c gi l c php RDF.

Web ng ngh a yu cu d liu khng nhng my c th c c m cn

mong mun my c th hiu c. Trch dn cu ni c$a Tim Berners Lee:

The semantic web goal is to be a unifying system which will (like the web for

human communication) be as un-restraining as possible so that the complexity of

reality can be described.

Tm dch l: M!c ch c$a web ng ngh a l mt h thng hp nh#t (ging

nh web dnh cho s giao tip c$a ngi) cng khng b cn tr cng tt m

phc tp c$a thc t c th c m t.

Vi web ng ngh a, n s* d- dng nhn bit ton b phm vi c$a cc cng c!

v ng d!ng kh gii quyt trong khun kh. c$a web hin ti.

Hai cng ngh quan trng cho vic pht trin semantic web l: eXtensible

Markup Language (XML) v Resource Description Frameword (RDF). XML cho

php mi ngi c th to ra cc tag (th, ) c$a ring mnh. Cn RDF th trnh by ng

ngh a, RDF s% d!ng tp cc triple m t cc khi nim c s.

URI ( Uniform Resource Identifier):

Mt URI n gin dng nhn bit mt trang web: ging nh cc chui bt

u vi http hay ftp m bn thng th#y trn word wide web. B#t k3 ai c/ng c

th to ra mt URI v quyn s hu chng c u4 quyn mt cch r rng, chnh v

vy chng to nn c s quan nim xy dng web ton cu. Thc ra, word wide

web c th xem nh l: b#t k3 th g m c URI c coi nh l on the web.

Cc URIs l cc chui k t c th nhn bit cc ti nguyn trn web. Thng

qua vic s% d!ng URIs, chng ta c th s% d!ng cng cch "t tn n gin tham

chiu n cc ti nguyn di cc nghi thc (protocol) khc nhau nh l: HTTP, FTP,

GOPHER, EMAIL, .

URLs ( Uniform Resource Locator): l mt dng c s% d!ng rng ri c$a

URIs, c s% d!ng r#t ph. bin trn web, l cc a ch& c$a cc ti nguyn. M"c d

thng c bit n nh l cc URLs, nhng URIs c/ng c th c tham chiu n



cc khi nim trong semantic web. V d!, gi s% bn c mt quyn sch c tn l

Machine Learning, th URI c$a n s* nh sau:

http://www.cs.bris.ac.uk/home/pw2538/book/title#machinelearning

Lu l mi th trn web u c mt URI duy nh#t.

2.2.2. Kin trc

Web ng ngh a c xy dng theo m hnh kin trc phn tng g1m c 7

tng, cc tng nh sau:

Hnh 9: Kin trc t+ng c a Semantic web.

Tng Unicode + URI:

Nh0m bo m vic s% d!ng tp k t quc t v cung c#p phng tin nh

danh cc i tng trong Web ng ngh a.

Tng XML + NS + Lc 1 XML:

Cng vi cc nh ngh a v namespace v schema bo m r0ng ta c th tch

hp cc nh ngh a web ng ngh a vi cc chu5n da trn XML khc.

Tng RDF + Lc 1 RDF:

Dng siu d liu m t ti liu trn Web my c th hiu c chng.



Tng Ontology:

Lc 1 RDF cung c#p cc cng c! nh ngh a nhng t vng, c#u trc v

cc rng buc trong vic m t cho siu d liu v cc ti nguyn Web. Nhng lc

1 RDF cha tht s y $ cho vic m hnh ho v h tr suy lun trn Semantic

Web. Ngn ng Ontology OIL c ra l mt dng m rng c$a lc 1 RDF. N

cho php th hin ng ngh a hnh thc, gip h tr suy di-n t ng.

Tng Logic:

Tng logic c xem nh l mt c s lut trn Semantic Web. Bn ch#t c$a c

s lut ny c dng nh mt h chuyn gia. Tng ny s* h tr cc dch v! nh : phn

loi vn bn, rt trch d liu.

Tng Proof:

Trong khi tng logic gip h tr suy lun da vo c s lut th tng Proof c

dng chng minh cc suy di-n c$a h thng b0ng cch lin kt cc d kin.

Tng Trust:

Trong Web ng ngh a cc thng tin c s% d!ng chung nh mt c s d liu

ton cu, nn cn phi c mt ci g bo mt. l nguyn nhn c$a s ra i

c$a ch k in t%, n gip cho thng tin trn Web ng tin cy hn. Trust engine l

mt h thng ang c xy dng da trn nn tng c$a ch k in t%. Cc k thut

xy dng chng cn ang trong giai on nghin cu v th% nghim.

2.2.3. Cc thch th'c t ra cho Semantic web

2.2.3.1. Thch th'c 1: Tnh s5n c c a ni dung (The availability

of content)

Ni dung c$a web ng ngh a l ni dung web c ch thch theo cc ontology

"c bit, cc ontology ny nh ngh a ng ngh a c$a cc t ho"c cc khi nim xu#t

hin trong cng mt ni dung. Mt s m rng n gin i vi HTML l c dng

ch thch cc trang web vi thng tin v ontology. Vic to ni dung semantic web

l mt thch thc ln, bi v c s h tng c$a semantic web vn cn ang c xy



dng (cha hon ch&nh RDF, OIL, DAML+OIL,), hin ti c r#t t ni dung web

ng ngh a c s6n.

2.2.3.2. Thch th'c 2: Cc ontology s5n c, pht tri6n v tin ho

Cc ontology l cha kha i vi semantic web bi v chng l nhng b

chuyn ch ng ngh a c cha trong semantic web, c ngh a l chng cung c#p mt

tp t vng v ng ngh a ch thch. C 3 v#n chnh cn c gii quyt i vi

thch thc ny, hai v#n u c lin quan n cc v#n v vic pht trin cc

ontology truyn thng m cho n tn by gi cc v#n ny vn cha c gii

quyt, v v#n th ba cn li c lin quan nhiu n khung cnh mi c$a semantic

web:

V#n th nh#t l vic xy dng cc ontology ht nhn (kernel) c s%

d!ng bi t#t c cc domain. Nhng khi u t1n ti i vi vic xy dng mt s

kernel ontology ny l chng phi c ng d!ng trong nhng domain khc nhau.

V#n th hai l cung c#p s h tr mang tnh ch#t gii php v cng ngh i

vi hu ht cc hot ng c$a tin trnh pht trin ontology, bao g1m:

a. S thu thp tri thc, m hnh khi nim v m ho ontology trong cc

ngn ng semantic web (RDFS, OIL, DAML+OIL), v cc ngn ng

mi cc ngn ng mi ny c th s* c a ra trong nhng nm sp

ti [Maedche, Staab 2001] .

b. S sp xp v nh x ontology, s tch hp ontology, cc cng c!

chuyn .i ontology, v cc cng c! xy dng ontology, nu cc

ontology t1n ti sp c s% d!ng li [Fensel et al, 2001], [Noy, Musen

2000].

c. Cc cng c! kim tra tnh bn vng cho cc ontology c s% d!ng li

[Gomez-Perez 1996].

V#n th ba l s tin ho c$a cc ontology v mi quan h c$a chng i vi

cc d liu c ch thch. Cc cng c! qun l c#u hnh l cn thit cho s iu

khin cc phin bn c$a mi ontology c/ng nh s ph! thuc ln nhau gia chng v



cc ch thch. T#t c cc v#n ny c th l khng quan trng lm, nhng cn thit

phi gii quyt trc khi mt semantic web thc s ra i.

2.2.3.3. Thch th'c 3: Scalability of semantic web content

Mt khi chng ta c ni dung c$a semantic web, chng ta s* phi quan tm

n vic phi qun l n nh th no, c ngh a l cch t. chc n nh th no, ni lu

tr n v cch tm c ni dung ng n. C 2 v#n chnh trong thch thc

ny:

a. V#n th nh#t c lin quan n vic lu tr v t. chc c$a cc trang

web ng ngh a (semantic web pages). Semantic web c s bao g1m

cc trang c ch thch da trn ontology, c#u trc lin kt c$a cc

trang ny phn nh c#u trc c$a WWW, c ngh a l cc trang lin kt

vi nhng trang khc thng qua cc hyperlink. Theo cch lin kt ny

(hyperlink) th khng khai thc c y $ ng ngh a c$a cc trang

web ng ngh a. Chin lc semantic indexes c xu#t gom

nhm ni dung c$a semantic web da trn cc ch$ c! th. Semantic

indexes s* c pht sinh t ng b0ng cch s% d!ng thng tin c$a

ontology v cc ti liu c ch thch.

b. V#n th hai c lin quan n vic d- dng tm kim thng tin trn

semantic web, ni cch khc l c lin quan n vic phi hp gia cc

semantic indexes.

2.2.3.4. Thch th'c 4: a ngn ng%

Vic hc da trn s phn tn c$a ngn ng thng qua ni dung c$a WWW ch&

ra r0ng thm ch nu ting Anh l ngn ng u th hn i vi cc ti liu, mt s ti

nguyn c vit b0ng ngn ng khc c/ng r#t quan trng: Ting Anh 68,4%; Ting

Nht 5,9%; Ting c 5,8%; Ting Trung Quc 3,9%; Ting Php 3,0%; Ting Ty

Ban Nha 2,4%; Ting Nga 1,9%; Ting Italia 1,6%; Ting B1 o Nha 1,4%; Ting

Hn 1,3%; Cc ngn ng khc 4,6% [www.vilaweb.com]. Tnh a dng c$a ngn ng

cn quan trng hn nhiu i vi cc ti nguyn WWW. a ngn ng ng vai tr



ngy cng ln i vi cc c#p sau: c#p ontology, c#p ch thch, v c#p

giao din ngi dng.

( c#p ontology, nhng ngi thit k ontology c th mun s% d!ng ngn

ng a phng c$a mnh cho vic pht trin ontology m trong cc ch thch s*

c gn vo. Bi v khng phi t#t c ngi s% d!ng u l nhng ngi xy dng

ontology, nn c#p ny c u tin th#p nh#t. S t1n ti cu a ngn ng v cc ti

nguyn ngn ng hc, nh l WordNet [wordnet], EuroWordnet [eurowordnet],c

th c xem xt t& m& h tr v#n a ngn ng c#p ny.

( c#p ch thch (annotation), ch thch c$a ni dung c th c thc hin

trong nhiu ngn ng khc nhau. Bi v nhiu ngi dng ("c bit l cc nh cung

c#p ni dung) s* thch ch thch ni dung hn l pht trin cc ontology, s h tr ph

hp l cn thit phi cho cc nh cung c#p ( ni dung ) ch thch ni dung b0ng

ngn ng a phng c$a h. c th pht sinh ni dung web ng ngh a b0ng t#t c

kh nng, chng ta khng th yu cu ch thch ni dung t ting Php sang ting c

c v ngc li.

Cui cng c#p giao din ngi dng, hng t& ngi mun truy xu#t vo ni

dung thch hp b0ng ngn ng a phng c$a h b#t ch#p ngn ng ngu1n ngn

ng m trong cc ch thch c trnh by. M"c d hin ti, a s ni dung u

c vit b0ng ting Anh, chng ta hy vng r0ng s* c nhiu ni dung hn c vit

b0ng nhiu ngn ng khc. B#t k3 hng tip cn no c$a semantic web c/ng nn bao

g1m cc tin ch truy xu#t thng tin trong nhiu ngn ng. Cc cng ngh quc t ho

v a phng ho nn c xem xt c5n thn i vi vic truy xu#t thng tin c nhn

da trn ngn ng a phng c$a ngi dng.

2.2.3.5. Thch th'c 5: Visualization s# m7ng tng

Vi s gia tng thng tin vt bc, s mng tng (hnh dung) c$a trc gic

v thng tin s* tr nn r#t quan trng, bi v ngi dng s* yu cu s d- dng

nhn bit s ph hp c$a ni dung cho m!c ch c$a h ngy cng gia tng. Thm vo

vic s% d!ng semantic indexes v cc routers cho vic lu tr, t. chc v tm kim



thng tin, v sau ny s* yu cu mt bc quan trng trong s mng tng. Cc

cng ngh nn cho php i vi cc cng ngh 3 chiu v s mng tng mi

mng tng ra ni dung c$a semantic web trong b#t k3 mt ngn ng web hin ti

no (RDFS, OIL, DAML + OIL). Thng qua cng ngh hin th 1 ho thi gian thc

3D tho ng v vic khai thc cc mi quan h ng ngh a, mt giao din ba chiu

mi c th c pht sinh mt cch t ng. Theo cch ny, nhiu thng tin hn c

th c trnh by trong mt khng gian nh2 hn, v ngi dng c th tng tc vi

cc site mt cch thc t v tin li [Van Harmelen et al 2001].

2.2.3.6. Thch th'c 6: S# chu,n ho cc ngn ng% semantic web

Semantic web l mt l nh vc ang n.i bt v WWW Consortium s* a ra cc

gii thiu v cc ngn ng v cng ngh s* c s% d!ng. vn ln n mc ngh

thut trong semantic web, v cc cng c! phn ln ph! thuc vo ngn ng semantic

web m chng c h tr, th nhu cu chu5n ho ngn ng semantic web l mt i

h2i cn thit.

2.2.4. So snh web v web ng% ngh!a

im ging nhau gia Web v Web ng ngh a: c 2 u dng nhng lin kt

(link) URI, nhng Web ng ngh a s% d!ng cc link ny r#t nhiu, vic s% d!ng link

lm gia tng tnh chnh xc c$a thng tin.

S khc nhau c bn gia Web v Web ng ngh a:

Web ng% ngh!a Web

Web ng ngh a l mt khng gian

thng tin trong thng tin c biu

di-n thng qua mt ngn ng m my

v ngi u c th hiu c.

Web l mt khng gian thng tin cha

ng thng tin ch& hng vo vic biu

di-n trong mt ngn ng t nhin m

ch& c ngi mi hiu c.

Web ng ngh a l mt d liu lin kt

vi nhau mt cch ng ngh a v hnh

thc.

Web l mt tp hp thng tin lin kt

vi nhau mt cch khng hnh thc.



2.2.5. Cc khi ni&m lin quan

2.2.5.1. Metadata

Metadata l thng tin c c#u trc m t, gii thch, nh v ho"c m"t khc

lm cho d- dng truy v#n, s% d!ng, qun l mt ti nguyn thng tin. Metadata thng

c gi l d liu v d liu (t in d liu), ho"c l thng tin v thng tin.

Metadata l thng tin v thng tin, metadata c s% d!ng rng ri trong

th gii thc cho m!c ch tm kim. V d!, bn mun mn mt vi quyn sch

mt th vin no thng qua my tnh. Thng th th vin s* cung c#p mt h

thng tra cu, h thng ny cho php bn lit k sch theo tn tc gi (author), theo

ta sch (title), theo ch$ (subject), v.v. Danh sch lit k ny cha nhiu thng

tin quan trng nh: tn tc gi, ta sch, ISBN, v thng tin quan trng nh#t l ni c#t

gi sch. Bn cn vi thng tin (trong trng hp ny l ni c#t gi sch) m bn

mun bit v bn s% d!ng metadata (trong trng hp ny l: tn tc gi, ta sch, v

ch$ ) l#y c sch.

C 3 kiu metadata:

a. Descriptive metadata: m t mt ti nguyn cho nhng m!c ch nh l

khm ph ho"c l nhn din. N c th bao g1m cc phn t% nh l:

titles, astract, author, v keywords.

b. Structural metadata: v d!: cho bit cc i tng phc hp lin kt vi

nhau nh th no, cc trang (pages) c sp xp thnh cc chng nh

th no.

c. Administrative metadata: cung c#p thng tin gip cho vic qun l mt

ti nguyn, nh l n c to ra khi no v nh th no, kiu file, v

cc thng tin k thut khc, v nhng ai c th truy cp n n.

2.2.5.2. Namespace

Chng ta c th m rng tp t vng c$a chng ta thng qua cc

namespace l cc nhm c$a tn cc phn t% v tn cc thuc tnh. Gi s%, nu bn

mun gp (include) mt k hiu (symbol) c m ho trong mt ngn ng nh d#u



no trong mt ti liu XML, th bn c th khai bo mt namespace ( khng gian

tn) m symbol thuc v. Thm vo , chng ta c th trnh c tnh hung hai

i tng XML trong cc khng gian tn khc nhau vi cng mt tn m c ngh a

khc nhau thng qua cc "c trng c$a cc namespace. Gii php l gn mt tin t

nhn bit namespace m mi phn t% ho"c cc thuc tnh thuc v. C php c$a

namespace nh sau:

ns-prefix:local-name

Trong ns-prefix l tn c$a namespace, v local-name l tn c$a phn

t% ho"c thuc tnh.

V d! v namespace:

Ti liu XML di y l mt th vin sch. Chng ta bt u b0ng phn

t% gc c tn th, l , bn trong th, gc cha cc phn t% sch v ta

sch nh sau:

Earthquakes for lunch

Khng gian tn cc b (local namespace):

Chng ta c th "t thuc tnh xmlns phn t% gc hay b#t k3 th, no khc.

Khi thuc tnh ny khng n0m trong th, gc th ta gi l khng gian tn c!c b.

V d!: Xem on xml di y:



Earthquakes for lunch.

Earthquakes for lunch.

Trong v d! ny th namespace: xmlns:amazon=http://www.amazon.com.lib

c gi l khng gian tn c!c b.

2.2.6. Ontology

Thut ng ontology c vay mn t trit hc. ngh a u tin c$a n l

the branch of metaphysics that deals with the nature of being [The American

Heritage Dictionary of the English Language: Fourth Edition (2000)].

Ontology l mt cng ngh quan trng mang tnh ch#t xng sng, v n cung

c#p mt "c tnh quan trng: ontology giao tip c gia ng ngh a hnh thc m

my tnh c th hiu c vi ng ngh a c$a th gii thc m con ngi c th hiu

c.

Nhng Ontology c pht trin trong tr tu nhn to tri thc d- dng chia

s, v s% d!ng li. K t u thp nin 90 c$a th k4 XX, Ontology tr thnh mt

ti nghin cu ph. bin i vi cc t. chc nghin cu tr tu nhn to, bao g1m

nhng k s v tri thc (Knowledge), x% l ngn ng t nhin v trnh by tri thc.

Ontology khng ch& lm cho tri thc c th s% d!ng li d- dng hn, n cn l

nn tng c$a vic to ra cc chu5n bi v n lm r cc khi nim bn cnh mt thut

ng ho"c mt m hnh. Yu cu trn thc t khng phi ch& dnh cho mt khi nim



duy nh#t, m l i vi mt s tng tc m h1 gia cc khi nim phc tp v chi tit

( c th c trnh by trong nhiu ngn ng khc nhau).

Gn y, khi nim Ontology tr nn ph. bin hn nhiu trong cc l nh vc

nh s tch hp thng minh, nhng h thng thng tin hp tc, ph!c h1i thng tin,

giao dch thng mi in t%, v qun l tri thc. M!c ch c$a Ontology l hng

n tri thc min, nn s pht trin c$a n thng l mt qu trnh x% l ko theo

nhiu yu t khc.

T lc ra i n nay, Ontology c r#t nhiu nh ngh a. Tuy nhin, "c

im ct li c$a Ontology vn l: Mt ontology l mt s ch& nh tng minh, hnh

thc v chia s v mt khi nim dng chung. Trong :

Mt khi nim tham chiu n mt m hnh tru tng c$a mt

vi hin tng no trong th gii thc m xc nh nhng khi

nim c lin quan v hin tng .

Tng minh l nhng khi nim v nhng rng buc trn n c

s% d!ng mt cch r rng.

Hnh thc tham chiu n cng vic m ontology phi thc hin

my tnh c th hiu c.

Chia s phn nh r0ng mt ontology gi tri thc 1ng nh#t, ngh a

l n khng b hn ch bi mt c nhn hay mt nhm ring l,

no.

Hin nay c nhiu ontology ln nh: CYC, WordNet, .

V d! v ontology:



Hnh 10: Mt Ontology n gin

2.2.7. Rdf

2.2.7.1 Khi ni&m :

RDF l t vit tt c$a Resource Description Framework. RDF c c% bi

W3C cho mt m hnh v ngn ng siu d liu (metadata) chu5n. RDF l mt b

khung cho vic m t cc ti nguyn trn web.

RDF cung c#p m hnh d liu v c php cc phn c lp nhau c th

chuyn .i cho nhau v s% d!ng c RDF.

2.2.7.2 C(u trc :

RDF l khung sn (framework) cho vic x% l metadata, v n m t cc mi

quan h gia cc ti nguyn thng qua cc thuc tnh v cc gi tr. RDF c xy

dng da trn cc lut nh sau:



Resource: Mi th c m t b0ng biu thc RDF c gi l mt

resource ( ti nguyn). Mi ti nguyn c mt URI v n c th l ton b trang web

ho"c l mt phn c$a trang web.

Property: Property l mt kha cnh, "c trng, thuc tnh ho"c quan h

ring bit c dng m t mt ti nguyn trch trong W3C, Resource

Description Framework (RDF) Model and Syntax Specification. Ch l mt

property c/ng c th l mt resource bi v n c nhng tnh ch#t ring c$a n.

Statements: Mt statements c dng kt hp mt resource, mt

property v mt value c$a n. Ba phn ring bit ny c bit nh l subject,

predicate, v object. V d!, The Author of

http://www.cs.bris.ac.uk/home/pw2538/index.html is Peng Wang l mt statement.

Ch r0ng value c$a cu ny c th l mt chui k t m c/ng c th l mt

resource.

V d v RDF:

Mt statement ( pht biu ) c th c xem nh l mt 1 th trong RDF.

Pht biu nh sau:

The Author of http://www.cs.bris.ac.uk/home/pw2538/index.html is

Peng Wang

Cu trn c phn tch thnh 3 phn:

Subject ( Resource ) http://www.cs.bris.ac.uk/home/pw2538/index.html

Predicate (Property) Author

Object (Literal) Peng Wang

c biu di-n di dng 1 th nh sau:



Chiu c$a m/i tn lun hng t subject n object c$a pht biu ( statement).

V 1 th c th c theo cch sau: HAS , v d!:

http://www.cs.bris.ac.uk/home/pw2538/index.html has author Peng Wang.

Nu chng ta gn mt URI cho thuc tnh author, th s* c :

http://www.cs.bris.ac.uk/home/pw2538/terms/author

trnh by ngn gn, chng ta a ra mt s tin t ( prefix) trnh phi

vit li ton b a ch& URI tham chiu n. C mt s tin t gn lin vi cc URI

c s% d!ng rng ri sau:

Tin t rdf: l khng gian tn cho URI:

http://www.w3.org/1999/02/22-rdf-syntax-ns#

Tin t rdfs: l khng gian tn cho URI:

http://www.w3.org/2000/01/rdf-schema#

Tin t daml: l khng gian tn cho URI:

http://www.daml.org/2001/03/daml+oil#

Tin t xsd: l khng gian tn cho URI:

http://www.w3.org/2001/XMLSchema#

Trong v d! ny, chng ta dng khng gian tn l pwterms i din cho a

ch& URI m ta tham chiu n: http://www.cs.bris.ac.uk/home/pw2538/terms

Khi c php RDF cho cu pht biu: The Author of

http://www.cs.bris.ac.uk/home/pw2538/index.html is Peng Wang l:

1

2

3

4

5

6

7

Peng Wang



Mt cu pht biu khc: Mt ngi c m s sinh vin l pw2538 c tn l

Peng Wang v c a ch& email l [email protected] . Ngi ny l tc gi c$a ti

nguyn http://www.cs.bris.ac.uk/home/pw2538/index.html

C 1 th nh sau:

C c php RDF:



M hnh d% li&u RDF (RDF Data Model):

RDF cung c#p mt m hnh cho vic m t cc ti nguyn. Ti nguyn c cc

tnh ch#t (property) thuc tnh ho"c l "c trng. RDF nh ngh a ti nguyn nh l

mt i tng b#t k3 c th nhn bit duy nh#t b0ng mt URI. Cc property c kt

hp vi cc ti nguyn c nhn bit bi cc property types, v cc property

types ny c cc values tng ng. Property types m t mi quan h c$a cc values

c kt hp vi cc ti nguyn. Trong RDF, cc values c th c xem nh l

nguyn t% trong t nhin ( chui text, s, v.v) ho"c l cc loi ti nguyn khc.

Bn ch#t ct li c$a RDF l mt m hnh c lp c php cho vic trnh by cc

ti nguyn v s m t tng ng c$a chng.



Hnh 11: M hnh d% li&u RDF

M hnh d liu RDF l mt 1 th c gn nhn nh hng, trong cc nt l cc ti

nguyn (nhng thc th vi URI) ho"c nhng k t, v cc cnh l nhng thuc tnh. Nh

gii thiu, mt pht biu RDF l mt b ba (Ch$ ng, V ng, B. ng). Trong , ti nguyn

l Ch$ ng c$a mt pht biu c thuc tnh m gi tr c$a n l B. ng c$a mt pht biu.

Mt B. ng c th l ti nguyn ho"c c th l mt gi tr k t. Mt pht biu c th c

i din nh mt 1 th, b0ng cch v* mt cung t mt nt (Ch$ ng) n nt khc (B. ng).

RDF l mt cch thnh lp cho vic x% l siu d liu, n cung c#p

interoperability (thao tc gia cc phn) gia cc ng d!ng m chuyn .i thng tin

my c th hiu c trn web. RDF nh#n mnh cc tin ch c th x% l t ng

cc ti nguyn web.

2.2.7.3 RDF Schema mt ngn ng% m t t" v#ng

Ngn ng c nh ngh a trong "c t ny (specification) g1m mt tp hp

cc ti nguyn m c th c s% d!ng m t cc thuc tnh c$a cc ti nguyn

RDF khc ( bao g1m c cc thuc tnh) nh ngh a tp t vng RDF c$a ng d!ng

xc nh. Tp t vng ny ch$ yu c nh ngh a trong mt khng gian tn c

gi l rdfs, v c nhn bit bi tham chiu URI: http://www.w3.org/2000/01/rdf-



schema#. "c t ny c/ng s% d!ng tin t rdf tham chiu n khng

gian tn RDF chnh: http://www.w3.org/1999/02/22-rdf-syntax-ns#.

H thng class v property trong RDF Schema c/ng tng t nh cc h thng

kiu c$a cc ngn ng hng i tng nh Java. Tuy nhin, RDF khc vi cc h

thng khc ch thay v nh ngh a mt class trong quan h c$a cc thuc tnh m th

hin c$a n c th c, RDF Schema s* nh ngh a cc thuc tnh trong quan h c$a cc

lp c$a ti nguyn m chng ng d!ng. y l nhim v! c$a rdfs:domain v

rdfs:range c m t trong "c t ny. V d!, chng ta c th nh ngh a thuc tnh

eg:author, c min l eg:Document v gii hn l eg:Person, nhng tri li mt h

thng hng i tng kinh in c th nh ngh a mt cch "c trng mt class

eg:Book vi mt thuc tnh c gi l eg:author c$a kiu eg:Person.

T" v#ng Domain and Range

"c t ny gii thiu tp t vng RDF cho vic m t cch s% d!ng y $ ng

ngh a c$a cc property v cc class trong d liu RDF. V d!, mt lc 1 RDF c th

m t gii hn trn cc kiu c$a cc value thch hp vi mt s thuc tnh.

RDF Schema cung c#p c ch (k thut) cho vic m t thng tin ny, nhng khng

th ni trong trng hp no th ng d!ng nn s% d!ng n v s% d!ng nh th no.

Cc ng d!ng khc nhau s* s% d!ng thng tin ny theo nhiu cch khc nhau. V d!,

cc cng c! kim tra d liu c th s% d!ng thng tin ny tm ra cc li trong

dataset, mt trnh son tho giao tip gia ngi v my c th ngh nhng gi tr

thch hp, v mt ng d!ng suy lun c th s% d!ng n suy lun r1i a ra thng tin

mi t d liu ban u.

Lc 1 RDF (RDF Schema) c th m t cc mi quan h gia cc t vng t

nhiu lc 1 c pht trin c lp nhau. Bi v tham chiu URI c s% d!ng

nhn bit cc class v property trn web, nn n c th to ra cc thuc tnh (property)

mi c domain v range m gi tr c$a n c nh ngh a trong mt namespace khc.

"c t ny khng c gng lit k t#t c cc hnh thc c th c c$a vic m

t t vng m n c s% d!ng trnh by ng ngh a c$a cc class v property c$a



RDF. Thay vo , chin lc m t t vng RDF tha nhn r0ng c nhiu k thut

m thng qua ng ngh a c$a cc class v property c cho bit, v xu#t bn

mt s quy c cho vic s% d!ng RDF/XML m t cc "c trng c$a cc class v

property cu RDF.

Lc 1 tt hn ho"c l cc ngn ng ontology nh l DAML+OIL, W3C,

cc ngn ng suy lun da trn lut, v cc ch$ ngh a hnh thc khc, mi loi s* gp

phn cho kh nng c$a chng ta nm bt c s t.ng hp y $ ng ngh a v d

liu trn web. Cc nh thit k t vng RDF c th to v pht trin cc ng d!ng web

ng ngh a b0ng cch s% d!ng tin ch The basic RDF Schema 1.0, trong khi trnh by

cc ngn ng m t t vng tt hn cch ny c/ng s% d!ng hng tip cn ny.

S lc v RDF Schema

Bng ny trnh by mt cch t.ng qut v tp t vng c s c$a RDF

Tn lp Ghi ch

rdfs:Resource The class resource, everything.

rdfs:Literal This represents the set of atomic values, eg.

textual strings.

rdfs:XMLLiteral The class of XML literals.

rdfs:Class The concept of Class

rdf:Property The concept of a property.

rdfs:Datatype The class of datatypes.

rdf:Statement The class of RDF statements.

rdf:Bag An unordered collection.

rdf:Seq An ordered collection.

rdf:Alt A collection of alternatives.



rdfs:Container This represents the set Containers.

rdfs:ContainerMembershipProperty

The container membership properties, rdf:1,

rdf:2, ..., all of which are sub-properties of

'member'.

rdf:List The class of RDF Lists

Bng 3 : Cc lp trong RDF

Property name comment domain range

rdf:type Indicates membership of a class rdfs:Resource rdfs:Class

rdfs:subClassOf Indicates membership of a class rdfs:Class rdfs:Class

rdfs:subPropertyOf Indicates specialization of

properties rdf:Property

rdf:Propert

y

rdfs:domain A domain class for a property type rdf:Property rdfs:Class

rdfs:range A range class for a property type rdf:Property rdfs:Class

rdfs:label Provides a human-readable

version of a resource name. rdfs:Resource rdfs:Literal

rdfs:comment Use this for descriptions rdfs:Resource rdfs:Literal

rdfs:member a member of a container rdfs:Container not

specified

rdf:first The first item in an RDF list. Also

often called the head. rdf:List

not

specified

rdf:rest

The rest of an RDF list after the

first item. Also often called the

tail.

rdf:List rdf:List



rdfs:seeAlso

A resource that provides

information about the subject

resource

rdfs:Resource rdfs:Resour

ce

rdfs:isDefinedBy Indicates the namespace of a

resource rdfs:Resource

rdfs:Resour

ce

rdf:value

Identifies the principal value

(usually a string) of a property

when the property value is a

structured resource

rdfs:Resource not

specified

rdf:subject The subject of an RDF statement. rdf:Statement rdfs:Resour

ce

rdf:predicate the predicate of an RDF statement. rdf:Statement rdf:Propert

y

rdf:object The object of an RDF statement. rdf:Statement not

specified

Bng 4:Cc thuc tnh c$a RDF

(M t cc t vng c$a RDF c trnh by trong phn Ph! l!c [1].)

2.3. eDoc

2.3.1. Tm hi6u eLearning

2.3.1.1. Khi ni&m

eLearning hay cn gi l Online Learning, chu5n cho t#t c cc hnh thc c$a

vic hc.



Online learning lin quan n vic s% d!ng cc cng ngh mng ( nh l:

Internet hay l mng thng mi bussiness network) cho vic phn pht, h tr,

nh gi vic dy hc chnh qui v khng chnh qui.

Hc xy ra u v nh th no? (: cc ti nguyn v cc ti liu trc tuyn,

cc th vin in t%, cc ti liu; v cc kho hc, cc bu.i tho lun, chats, email, hi

ngh, v cc ng d!ng chia s, tri thc. Mt ch quan trng l online learning khng

nh#t thit phi di-n ra trc tuyn (online). S% d!ng cng ngh cho vic hc thng l

mt yu t ph! i vi lp hc v cc c hi hc trc tip ( face to face ).

Mt s nguyn nhn s% d!ng online learning:

a. Vic truy cp c ci thin v tnh linh ng: Mi ngi c th ng

nhp vo b#t k3 mt my tnh no, ti nh ho"c ni lm vic, vo b#t

k3 lc no k c ngy ln m, l#y bi hc ho"c tham kho n cc

ti liu hc.

b. Phn phi nhanh hn v tit kim chi ph: i vi cc t. chc cn truyn

t thng tin quan trng m thng tin ny nhanh chng tr nn li thi (

v d!, phin bn mi nh#t c$a mt sn ph5m), th hnh thc online hu

nh l r, hn v nhanh hn nhiu so vi vic ngi truyn t phi bay

qua nhiu quc gia g"p g nhng hc vin lp hc vi hng ting

1ng h1.

c. Ci tin vic iu hnh v chu5n ho: Trong mi trng thng mi

quc t ngy nay, nhiu t. chc m rng trn phm vi ton cu. S khc

nhau v kin thc v k nng c$a cc c nhn dy c th s* lm cho ch#t

lng hc c$a cc hc vin nhng ni khc nhau s* khc nhau: v d!

nhng ngi hc New Delphi s* c ch#t lng hu#n luyn khc vi

nhng ngi New York. Online learning cung c#p thng tin nh#t qun,

ph. bin i vi cc i tng khp ni.

Lm n.i bt thng tin truyn t v s cng tc: Thng qua nhng phn mm

no s* cho php nhng ngi hc c giao tip vi nhau, cng tc vi nhau qua

cc d n, v chia s, ti liu m khng cn phi g"p m"t trc tip.



2.3.1.2. Cc chu,n c a eLearning

Ngnh cng nghip eLearning tip t!c c m rng mi ngy, v cc chu5n

cn thit to ni dung bi hc ngy cng tr nn phc tp.

Trc khi mt qui c c$a eLearning tr thnh standards (chu5n), n c

gi l specification ( "c t ). Specification c duyt bi mt t. chc t. chc

ny c mi ngi cng nhn, nh l IEEE ch+ng hn.

Mt s chu5n c$a eLearning:

a. Tp phn t siu d liu Dublin Core

Tp phn t% siu d liu Dublin Core ( The Dublin Core metada element

set) l chu5n cho s m t ti nguyn thng tin xuyn domain (bng qua nhiu

domain). ( y, ti nguyn thng tin c nh ngh a l b#t k3 th g m c th

nhn bit c. i vi cc ng d!ng Dublin Core, mt ti nguyn s* l mt ti

liu in t% (electronic document).

Siu d liu Dublin Core c dng cho vic tm kim v ch& m!c cho

cc siu d liu da trn Web. Tp siu d liu ny cung c#p t vng ng ngh a

nh: Description, Creator v Date cho vic m t nhng "c trng thng

tin quan trng c$a cc ti nguyn Internet.

Tp siu d liu Dublin Core cung c#p 15 t vng:

Title: Tn c gn cho ti nguyn.

Creator: Thc th c trch nhim to ra ti nguyn. V d! nh:

c nhn, t. chc hay mt dch v! no .

Subject: Ch$ ni dung c$a ti nguyn.

Description: M t ni dung c$a ti nguyn.

Publisher: Thc th c nhim v! to ra ti nguyn.

Contributor: Thc th c ng gp vo ni dung c$a ti nguyn.

Date: Ngy ti nguyn c to.

Type: Th loi ni dung c$a ti nguyn.

Format: Dng lu tr vt l c$a ti nguyn.



Identifier: Mt tham chiu c! th n ti nguyn trong mt ng

cnh cho php.

Source: Tham chiu n mt ti nguyn m ti nguyn c

dn xu#t.

Language: Ngn ng s% d!ng bi ni dung c$a ti nguyn.

Relation: Tham chiu n mt ti nguyn lin quan

Coverage: M rng ni dung c$a ti nguyn

Right: Thng tin v quyn s hu ti nguyn.

b. LOM (Learning Object Metadata)

LOM l mt chu5n v eLearning hin ti c pht trin bi t. chc

IEEE. T. chc chu5n ho cng ngh hc (Learning Technology Standards

Committee) c$a IEEE pht trin chu5n LOM nh0m gip cho vic s% d!ng v

s% d!ng li c$a cc ti nguyn hc c h tr cng ngh nh l vic hu#n

luyn da trn my tnh, v vic hc t xa.

Trong mt h thng eLearning, i tng hc l nhng g c th c s%

d!ng, k tha hay tham kho trong vic h tr cng ngh hc. Hin ti mt s

i tng ang c tip t!c pht trin nh0m p ng nhu cu hc thay .i

nhanh chng. Vic thiu thng tin hay siu d liu v i tng hc to ra

nhiu cn tr, hn ch cho kh nng qun l, khm ph v s% d!ng i tng

hc.

LOM gii quyt v#n trn b0ng cch nh ngh a mt c#u trc cho vic

m t mt i tng hc. LOM ch& ra c php v ng ngh a c$a cc siu d

liu i tng hc, nh ngh a cc thuc tnh nh0m m t y $ v tho ng

cc i tng hc.

M!c ch c$a LOM:

Cho php ngi hc hay ngi hng dn tm kim, nh gi i

tng hc.



Cho php chia s, v trao .i cc i tng hc qua b#t k3 cng ngh

c h tr h thng hc.

Cho php pht trin cc i tng hc theo cc n v c kh nng

kt hp hay phn r theo mt phng php ph hp.

Cho php cc agent my tnh linh ng l t ng trong vic t. chc

cc bi hc cung c#p n ngi hc.

N hon ton da trn chu5n v quan tm n cc i tng hc

trong mi trng m v phn tn.

Cho php cc cng ngh mi kt hp vi cc i tng hc.

Cung c#p cho cc nh nghin cu chu5n h tr v su tp d liu lin

quan n hiu qu c$a cc i tng hc.

LOM nh ngh a mt tp ti thiu cc thuc tnh (attributes) qun l,

nh v, v nh gi cc i tng hc. Cc thuc tnh c gom nhm thnh 8

phm tr:

General: cha ng thng tin v ton b i tng.

Lifecycle: cha ng siu d liu v s tin ho c$a cc i

tng.

Technical: vi s m t c$a cc "c trng v yu cu k thut.

Educational: cha ng cc thuc tnh v gio d!c ho"c s phm.

Rights: m t quyn s hu v cc iu kin s% d!ng

Relation: nhn bit cc i tng c lin quan vi nhau.

Annotation: cha ng cc ch thch v ngy, tc gi c$a cc ch

thch ny.

Classification: nhn bit cc b nhn din h thng phn loi

khc cho i tng.

Bn trong mi phm tr l mt tp cc phn t% d liu c th t, m gi

tr c$a chng l cc metadata. V d!: Cc phn t% siu d liu lin quan n

vic hc c tm th#y trong phm tr Education l Typical Age Range,

Difficulty, Typical Learning Time, v Interactivity Level.



c. vCard

vCard l chu5n c gii thiu v pht trin bi IMC (Internet Mail

Consortium). Cc thng tin c nhn thng thng r#t phc tp v c nhiu loi

khc nhau. Hin ti c mt s chu5n xu#t cc c#u trc cho vic trao .i

thng tin c nhn PDI (Personal Data Interchange). M!c ch c$a chu5n ny l

nh0m gii quyt nhu cu su tp v trao .i thng tin c nhn qua nhiu knh

thng tin khc nhau nh in thoi, th in t% hay i thoi trc tip.

Chu5n vCard ph hp cho vic trao .i d liu c nhn gia cc ng

d!ng v h thng. nh dng c$a vCard hon ton c lp vi phng php

dng truyn ti n. Vic truyn ti ny c th l trao .i mt h thng tp

tin, mng chuyn mch cng cng, mng dy dn hay mng khng dy. vCard

nhm n vic trao .i thng tin c nhn. Trong mi trng thng mi ngy

nay, thng tin ny thng c trao .i trn cc th, thng mi v vCard nh

ngh a nhng thng tin ny da trn cc i tng th, thng mi in t%.

d. SCORM (Shareable Content Object Reference Model)

SCORM nh ngh a m hnh kt hp gia ni dung v mi trng thc

thi cho cc i tng hc. y l mt m hnh tham chiu n mt tp cc k

thut lin quan vic thit k nh0m p ng yu cu ni dung hc da trn Web,

nhng yu cu ny bao g1m kh nng ti s% d!ng, truy xu#t, kh nng tng

tc c$a cc i tng hc.

e. IMS ( Instructional Management Systems)

IMS ang c pht trin v xc tin tr thnh chu5n m cho cc hot

ng eLearning nh s% d!ng, sp xp cc ni dung gio d!c v m rng cc

khi nim t.ng qut nh: thit k ngi hc, theo di v bo co qu trnh

ngi hc nh0m thc hin vic trao .i thng tin gia cc h thng hc khc

nhau.



M!c ch c$a IMS:

nh ngh a cc chu5n k thut nh0m nng cao kh nng tng tc

gia ng d!ng v dch v! trong mi trng hc phn tn hin nay.

H tr vic st nhp "c t c$a IMS vo trong cc sn ph5m v dch

v! trn ton th gii. S ch#p nhn "c t rng ri s* cho php phn

phi mi trng v ni dung hc t nhiu tc gi li vi nhau.

2.3.2. Tm hi6u eLib

Elib (electronic library hay c gi l digital library) l mt th vin 5n. T

electronic library ng! l mt su tp c$a cc ti nguyn thng tin in t% c ni

mng cng k thut lin kt v c s h tng qun tr. Bn c th truy cp n t b#t c

my PC hay laptop c ni mng no t b#t c ni no trn th gii b#t c thi im

no.

Elib lu tr v ch& m!c hng vn sch, bo, tp ch v $ cc ch$ trn th

gii, ch+ng hn nh vt l, thin vn, sinh ho, cng ngh sinh hc, ho hc v cng

trnh xy dng ho ch#t, cc thit b xy dng, cng trnh xy dng mi trng, khoa

hc thc ph5m, v an ton sc kho, v v sinh .v.v c/ng nh cc ti liu v thng

tin tiu s%, l lch c nhn, ngh nghip, cc t. chc, hi lin hip, v du lch v.v.

Th vin in t% ny c s% d!ng ph. bin nh#t trong cc trng i hc v nhng

trung tm nghin cu khoa hc. T#t nhin, i tng s% d!ng n chnh l nhng sinh

vin, nghin cu sinh v cc nh khoa hc.

Nhng chng trnh Electronic library c xy dng da trn nhng chu5n

thng nh#t do cc hi 1ng, t. chc ln trn th gii lp ra. Mt s t. chc nh chu5n

ln trn gii nh W3C (World Wide Web Consortium), ISO (International

Organization for Standardization), NISO (National Information Standards

Organization ), . C nhiu chu5n cho nhiu kha cnh khc nhau c$a vic lu tr v

truy cp thng tin in t%, bao g1m cc chu5n v thu h1i thng tin (Information

Retrieval Standard), thao tc gia cc phn (Interoperability), nh dng ti nguyn,



nhn dng ti nguyn, m t ti nguyn, Sau y l mt s chu5n s% d!ng trong

eLib lin quan n v#n truy cp thng tin in t%:

Chu,n v thu h.i thng tin:

Kiu chu5n ny cho php thng tin gia cc h thng khc nhau, lm cho thun

tin trong vic khm ph v truy cp thng tin in t%. V d! nh chu5n thu h1i thng

tin ISO 23950 (tng ng vi ANSI Z39.50) nh ngh a mt hng chu5n cho hai

my tnh lin lc v chia s, thng tin vi nhau. N c thit k h tr khm

ph ti nguyn v thu h1i ti nguyn c$a nhng ti liu full-text, d liu m!c l!c,

cc hnh nh v multimedia. Chu5n ny da trn kin trc client-server v c lp vi

cc h thng c! th, hon ton iu hnh trn Internet.

Z39.50:

Z39.50 l mt trong mt nhm cc chu5n c sn xu#t lm cho d- dng kt

ni cc h thng my tnh. Chu5n ny ch& ra cc nh dng v th$ t!c chi phi vic

trao .i cc thng ip gia client v server, cho php ngi dng c th tm kim cc

c s d liu t xa, nhn din cc dng d liu c nh r cc chu5n, v thu h1i mt

vi hay t#t c cc dng c nhn din v c lin quan, c! th vi vic tm kim v

thu h1i thng tin trong c s d liu. Mt trong nhng thun li ln trong vic s% d!ng

Z39.50 l n cho php truy cp nh nhau n mt s lng ln ngu1n thng tin thay

.i khc nhau.

Z39.50 tha nhn r0ng vic thu h1i thng tin g1m hai thnh phn chnh chn

thng tin da trn nhng tiu chu5n v thu h1i thng tin , v n cung c#p mt ngn

ng chung cho c hai hnh ng . Z39.50 chu5n ho cch x% s m trong client

v server thng tin vi nhau v hot ng ngay khi c nhng khc bit gia cc h

thng my tnh, cc cng c! tm kim v cc c s d liu.

EDI (Electronic Data Interchange)

EDI c bit n nh mt chu5n cng ngh thng tin quc gia. ( EDI, d liu

m theo truyn thng c chuyn vo trong cc ti liu gi#y th c truyn hay

c thng tin mt cch in t% ty vo cc lut v cc nh dng c thit lp. D



liu lin i vi mi kiu c$a ti liu chc nng, v d! nh bng mua bn hay ho n,

c vn chuyn ln nhau nh l mt thng ip in t%. D liu nh dng c th

c vn chuyn t ngi to ra n ngi nhn thng qua thng tin lin lc b0ng cp

hay vn chuyn vt l vo trong thit b lu tr in t%.

EDI a n mt chui cc thng ip gia hai ni, v d! ngi mua v ngi

bn, mi ngi c th xem nh l ngi to ra hay ngi nhn. Cc thng ip t

ngi mua n ngi bn s* bao g1m, v d! nh d liu cn thit cho yu cu i vi

s trch dn (request for quotation_ RFQ), cc bin lai mua bn, cc thng bo vic

vn chuyn tu thuyn, v cc ho n. Vic thc thi c$a EDI yu

Documents

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