tìm kiếm ngữ nghĩa ứng dụng trên lĩnh vực edoc
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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
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2
NHN XT CA GIO VIN HNG DN
....
Ngy thngnm 2005
K tn
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NHN XT CA GIO VIN PHN BIN
.
Ngy thngnm 2005
K tn
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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
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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$a ng t: .............................................................. 149
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DANH MC CC BNG
Bng 1 : Bng hng dn nhanh v cch s dng mt s search engine ph bin ......... 28 Bng 2: S lc v cc c trng c a mt s search engine thng dng trn Internet .. 32 Bng 3 : Cc lp trong RDF ............................................................................................ 54 Bng 4:Cc thuc tnh c a RDF........................................................................................... 55 Bng 5: Danh sch cc ngh!a v rng buc c a cc t" th#c trong cu............................. 77 Bng 6 M t c s$ 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
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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
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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
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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)
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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.
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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
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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
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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$a cng c! tm kim l:
(i) Cng c! tm kim cn cho php nhng truy v#n phc tp hn (v
d! trong ngn ng t nhin),
(ii) Cng c! tm kim cn hiu nhng g con ngi h2i, v
(iii) Cng c! tm kim phi cung c#p cu tr li cho truy v#n (c th
sao lu li nhng lin kt n cc ti liu m cho ra cu tr li).
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1.3. Hng tip c*n
C hai tip cn ci thin cc kt qu tm kim thng qua phng php ng
ngh a:
1. Kin trc c$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,
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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
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c$a cc cng c! tm kim ng ngh a l b. sung cho cc cng c! tm kim thng
thng, hn l cnh tranh nh nhng i th$ .
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0112274 Phm Th M Phng - 17 - 0112398 T Th Ngc Thanh
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$a web.
Nhng search engine sau l t#t c nhng la chn tt nh#t bt u khi tm kim
thng tin:
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2.1.1.1. Google: http://www.google.com/
Hnh 1: Giao di&n c a Google
Nguyn thu4, Google l mt n c$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
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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
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0112274 Phm Th M Phng - 20 - 0112398 T Th Ngc Thanh
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
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0112274 Phm Th M Phng - 21 - 0112398 T Th Ngc Thanh
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.
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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.
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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.
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0112274 Phm Th M Phng - 24 - 0112398 T Th Ngc Thanh
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$a Yahoo, AltaVista l mt chn la tt.
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2.1.1.8. Lycos: http://www.lycos.com/
Hnh 8: Giao di&n c a Lycos
Lycos l mt trong nhng cng c! tm kim c/ nh#t trn web, c a ra nm
1994. c m t nh l nhng c.ng truy cp web ( web portal ) hay nhng trung tm
truy cp, l ni m ngi dng i vo l#y thng tin cho mi l nh vc, k c tn gu,
gi th in t%,
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0112274 Phm Th M Phng - 26 - 0112398 T Th Ngc Thanh
Search
Engine
Google AlltheWeb AltaVista Teoma
Database google.com alltheweb.com altavista.com teoma.com
Kch thc(#
trang )
Khong 8 t& (1
t& khng nh
ch& m!c trn
ton vn bn)
Khong 3 t&,
ch& m!c trn
ton vn bn.
Khong 1 t& Khong 1 t&
a phng
tin
(multimedia)
H tr H tr H tr Khng h tr
Ton t%
M"c nh AND AND AND AND
Loi tr - - - -
C!m t Dng d#u Dng d#u Dng d#u Dng d#u
Rt gn Khng h tr
Dng k t *
thay th
cho cc k t
trong d#u
Khng h tr Dng k t * Khng h tr
Boolean OR (ch& dng
cho danh t
ring )
AND, OR,
ANDNOT,
RANK, ()
AND, OR,
ANDNOT,
NEAR, ()
OR (ch& dng cho tn
ring)
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0112274 Phm Th M Phng - 27 - 0112398 T Th Ngc Thanh
Stop words Thng thng
b2 qua cc t
thng d!ng
+ nu mun
tm v phi "t
trong c"p d#u
Dng d#u
trong search
c bn
B2 qua trong
search nng
cao
Thng thng b2 qua
cc t thng d!ng
+ nu mun tm
Danh t
ring
Khng h tr Khng h tr H tr Khng h tr
Gii hn
field cn tm
intitle:
inurl:
allintitle:
Allinurl:
filetype:
Link:site:
Trong search
nng cao :
cache:info:
Normal.title:
url.all:
Link.all:
Link.extension
:
Title:
domain:
Link:
image:
Text:
url:
host:
Anchor:
applet:
intitle:
inurl:
site:
geoloc:
lang:
last:
afterfate:
Cc "c tnh
"c bit
~ tm t 1ng
ngh a
Gii hn bi
ngn ng
Nhiu kiu file
: pdf, doc,
Caches : trang
web khi nh
ch& m!c
Duyt qua cc
URL
Trong tm
nng cao :
gii hn bi
ngy, domain,
a ch& iP
Gii hn bi
ngy, v tr,
ngn ng
Trong tm
nng cao : s%
d!ng sortby
lc v sp xp
kt qu.
Dng refine ti u
kt qu.
Resource c c
cc trang v lin kt
tp trung trn ch$
cn tm.
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0112274 Phm Th M Phng - 28 - 0112398 T Th Ngc Thanh
'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.
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0112274 Phm Th M Phng - 29 - 0112398 T Th Ngc Thanh
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
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0112274 Phm Th M Phng - 30 - 0112398 T Th Ngc Thanh
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$ .
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0112274 Phm Th M Phng - 31 - 0112398 T Th Ngc Thanh
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$a trang
kt qu.
Dn n cc
trang ph!c v!
hc tp : t in,
vt l, khoa hc,
bn 1, lch
s%,
Yahoo
http://dir.yaho
o.com
Xem xt cc
trang web
(khong 13K)
AND (m"c
nh)
OR
C!m t :
Rt gn : *
Fields t: title,
u:URL
Nhiu dch v!
trong Yahoo:
Tin tc : tng
gi.
Th thao :t& s,..
Bn 1, thi tit,
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0112274 Phm Th M Phng - 32 - 0112398 T Th Ngc Thanh
mua sm.
Bng 2: S lc v cc c trng c a mt s search engine thng dng trn Internet
2.1.2. Chin lc tm kim
T search engine thng c s% d!ng rng ri m t cc cng c! tm
kim da trn crawler v cc th m!c do con ngi cung c#p. y l hai loi c$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$a
con ngi.
B l*p ch3 mc Index
H thng lp ch& m!c hay cn gi l h thng phn tch v x% l d liu, thc
hin vic phn tch, trch chn nhng thng tin cn thit (thng l cc t n , t
ghp , c!m t quan trng) t nhng d liu m robot thu thp c v t. chc thnh
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c s d liu ring c th tm kim trn mt cch nhanh chng, hiu qu. H
thng ch& m!c l danh sch cc t kho, ch& r cc t kho no xu#t hin trang no,
a ch& no.
B tm kim thng tin Search Engine
Search engine l c!m t dng ch& ton b h thng bao g1m b thu thp
thng tin, b lp ch& m!c v b tm kim thng tin. Cc b ny hot ng lin t!c t
lc khi ng h thng, chng ph! thuc ln nhau v m"t d liu nhng c lp vi
nhau v m"t hot ng.
Search engine tng tc vi user thng qua giao din web, c nhim v! tip
nhn v tr v nhng ti liu tho yu cu c$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.
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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$a d liu URI c th c c#t gi trong c s d liu, ho"c thay th ln nhau
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0112274 Phm Th M Phng - 35 - 0112398 T Th Ngc Thanh
trn word wide web b0ng cch s% d!ng mt tp cc c php "c bit c php trin
chuyn bit ph!c v! cho nhim v! . C php ny c gi l c php RDF.
Web ng ngh a yu cu d liu khng nhng my c th c c m cn
mong mun my c th hiu c. Trch dn cu ni c$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
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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.
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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$a semantic web vn cn ang c xy
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dng (cha hon ch&nh RDF, OIL, DAML+OIL,), hin ti c r#t t ni dung web
ng ngh a c s6n.
2.2.3.2. Thch th'c 2: Cc ontology s5n c, pht tri6n v tin ho
Cc ontology l cha kha i vi semantic web bi v chng l nhng b
chuyn ch ng ngh a c cha trong semantic web, c ngh a l chng cung c#p mt
tp t vng v ng ngh a ch thch. C 3 v#n chnh cn c gii quyt i vi
thch thc ny, hai v#n u c lin quan n cc v#n v vic pht trin cc
ontology truyn thng m cho n tn by gi cc v#n ny vn cha c gii
quyt, v v#n th ba cn li c lin quan nhiu n khung cnh mi c$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
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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
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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$a h ngy cng gia tng. Thm vo
vic s% d!ng semantic indexes v cc routers cho vic lu tr, t. chc v tm kim
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thng tin, v sau ny s* yu cu mt bc quan trng trong s mng tng. Cc
cng ngh nn cho php i vi cc cng ngh 3 chiu v s mng tng mi
mng tng ra ni dung c$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$a thng tin.
S khc nhau c bn gia Web v Web ng ngh a:
Web ng% ngh!a Web
Web ng ngh a l mt khng gian
thng tin trong thng tin c biu
di-n thng qua mt ngn ng m my
v ngi u c th hiu c.
Web l mt khng gian thng tin cha
ng thng tin ch& hng vo vic biu
di-n trong mt ngn ng t nhin m
ch& c ngi mi hiu c.
Web ng ngh a l mt d liu lin kt
vi nhau mt cch ng ngh a v hnh
thc.
Web l mt tp hp thng tin lin kt
vi nhau mt cch khng hnh thc.
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2.2.5. Cc khi ni&m lin quan
2.2.5.1. Metadata
Metadata l thng tin c c#u trc m t, gii thch, nh v ho"c m"t khc
lm cho d- dng truy v#n, s% d!ng, qun l mt ti nguyn thng tin. Metadata thng
c gi l d liu v d liu (t in d liu), ho"c l thng tin v thng tin.
Metadata l thng tin v thng tin, metadata c s% d!ng rng ri trong
th gii thc cho m!c ch tm kim. V d!, bn mun mn mt vi quyn sch
mt th vin no thng qua my tnh. Thng th th vin s* cung c#p mt h
thng tra cu, h thng ny cho php bn lit k sch theo tn tc gi (author), theo
ta sch (title), theo ch$ (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
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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:
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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
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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:
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Hnh 10: Mt Ontology n gin
2.2.7. Rdf
2.2.7.1 Khi ni&m :
RDF l t vit tt c$a Resource Description Framework. RDF c c% bi
W3C cho mt m hnh v ngn ng siu d liu (metadata) chu5n. RDF l mt b
khung cho vic m t cc ti nguyn trn web.
RDF cung c#p m hnh d liu v c php cc phn c lp nhau c th
chuyn .i cho nhau v s% d!ng c RDF.
2.2.7.2 C(u trc :
RDF l khung sn (framework) cho vic x% l metadata, v n m t cc mi
quan h gia cc ti nguyn thng qua cc thuc tnh v cc gi tr. RDF c xy
dng da trn cc lut nh sau:
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Resource: Mi th c m t b0ng biu thc RDF c gi l mt
resource ( ti nguyn). Mi ti nguyn c mt URI v n c th l ton b trang web
ho"c l mt phn c$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$a cu ny c th l mt chui k t m c/ng c th l mt
resource.
V d v RDF:
Mt statement ( pht biu ) c th c xem nh l mt 1 th trong RDF.
Pht biu nh sau:
The Author of http://www.cs.bris.ac.uk/home/pw2538/index.html is
Peng Wang
Cu trn c phn tch thnh 3 phn:
Subject ( Resource ) http://www.cs.bris.ac.uk/home/pw2538/index.html
Predicate (Property) Author
Object (Literal) Peng Wang
c biu di-n di dng 1 th nh sau:
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Chiu c$a m/i tn lun hng t subject n object c$a pht biu ( statement).
V 1 th c th c theo cch sau: HAS , v d!:
http://www.cs.bris.ac.uk/home/pw2538/index.html has author Peng Wang.
Nu chng ta gn mt URI cho thuc tnh author, th s* c :
http://www.cs.bris.ac.uk/home/pw2538/terms/author
trnh by ngn gn, chng ta a ra mt s tin t ( prefix) trnh phi
vit li ton b a ch& URI tham chiu n. C mt s tin t gn lin vi cc URI
c s% d!ng rng ri sau:
Tin t rdf: l khng gian tn cho URI:
http://www.w3.org/1999/02/22-rdf-syntax-ns#
Tin t rdfs: l khng gian tn cho URI:
http://www.w3.org/2000/01/rdf-schema#
Tin t daml: l khng gian tn cho URI:
http://www.daml.org/2001/03/daml+oil#
Tin t xsd: l khng gian tn cho URI:
http://www.w3.org/2001/XMLSchema#
Trong v d! ny, chng ta dng khng gian tn l pwterms i din cho a
ch& URI m ta tham chiu n: http://www.cs.bris.ac.uk/home/pw2538/terms
Khi c php RDF cho cu pht biu: The Author of
http://www.cs.bris.ac.uk/home/pw2538/index.html is Peng Wang l:
1
2
3
4
5
6
7
Peng Wang
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Mt cu pht biu khc: Mt ngi c m s sinh vin l pw2538 c tn l
Peng Wang v c a ch& email l pw2538@bristol.ac.uk . Ngi ny l tc gi c$a ti
nguyn http://www.cs.bris.ac.uk/home/pw2538/index.html
C 1 th nh sau:
C c php RDF:
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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$a chng.
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Hnh 11: M hnh d% li&u RDF
M hnh d liu RDF l mt 1 th c gn nhn nh hng, trong cc nt l cc ti
nguyn (nhng thc th vi URI) ho"c nhng k t, v cc cnh l nhng thuc tnh. Nh
gii thiu, mt pht biu RDF l mt b ba (Ch$ 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-
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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
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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.
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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
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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.
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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$a cc hc vin nhng ni khc nhau s* khc nhau: v d!
nhng ngi hc New Delphi s* c ch#t lng hu#n luyn khc vi
nhng ngi New York. Online learning cung c#p thng tin nh#t qun,
ph. bin i vi cc i tng khp ni.
Lm n.i bt thng tin truyn t v s cng tc: Thng qua nhng phn mm
no s* cho php nhng ngi hc c giao tip vi nhau, cng tc vi nhau qua
cc d n, v chia s, ti liu m khng cn phi g"p m"t trc tip.
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2.3.1.2. Cc chu,n c a eLearning
Ngnh cng nghip eLearning tip t!c c m rng mi ngy, v cc chu5n
cn thit to ni dung bi hc ngy cng tr nn phc tp.
Trc khi mt qui c c$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$a ti nguyn.
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Identifier: Mt tham chiu c! th n ti nguyn trong mt ng
cnh cho php.
Source: Tham chiu n mt ti nguyn m ti nguyn c
dn xu#t.
Language: Ngn ng s% d!ng bi ni dung c$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$a LOM:
Cho php ngi hc hay ngi hng dn tm kim, nh gi i
tng hc.
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Cho php chia s, v trao .i cc i tng hc qua b#t k3 cng ngh
c h tr h thng hc.
Cho php pht trin cc i tng hc theo cc n v c kh nng
kt hp hay phn r theo mt phng php ph hp.
Cho php cc agent my tnh linh ng l t ng trong vic t. chc
cc bi hc cung c#p n ngi hc.
N hon ton da trn chu5n v quan tm n cc i tng hc
trong mi trng m v phn tn.
Cho php cc cng ngh mi kt hp vi cc i tng hc.
Cung c#p cho cc nh nghin cu chu5n h tr v su tp d liu lin
quan n hiu qu c$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.
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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$a cc i tng hc.
e. IMS ( Instructional Management Systems)
IMS ang c pht trin v xc tin tr thnh chu5n m cho cc hot
ng eLearning nh s% d!ng, sp xp cc ni dung gio d!c v m rng cc
khi nim t.ng qut nh: thit k ngi hc, theo di v bo co qu trnh
ngi hc nh0m thc hin vic trao .i thng tin gia cc h thng hc khc
nhau.
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M!c ch c$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$a vic lu tr v
truy cp thng tin in t%, bao g1m cc chu5n v thu h1i thng tin (Information
Retrieval Standard), thao tc gia cc phn (Interoperability), nh dng ti nguyn,
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nhn dng ti nguyn, m t ti nguyn, Sau y l mt s chu5n s% d!ng trong
eLib lin quan n v#n truy cp thng tin in t%:
Chu,n v thu h.i thng tin:
Kiu chu5n ny cho php thng tin gia cc h thng khc nhau, lm cho thun
tin trong vic khm ph v truy cp thng tin in t%. V d! nh chu5n thu h1i thng
tin ISO 23950 (tng ng vi ANSI Z39.50) nh ngh a mt hng chu5n cho hai
my tnh lin lc v chia s, thng tin vi nhau. N c thit k h tr khm
ph ti nguyn v thu h1i ti nguyn c$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
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ti: Tm kim ng ngh a ng d!ng trn l nh vc eDoc
0112274 Phm Th M Phng - 63 - 0112398 T Th Ngc Thanh
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