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I HC QUC GIA H NITRNG I HC CNG NGH

Trn Hoi Nam

CSDLIU A PHNG TIN

YU CU V CC VN

LUN VN THC S

H Ni 2004


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I HC QUC GIA H NI

TRNG I HC CNG NGH

Trn Hoi Nam

CSDLIU A PHNG TINYU CU V CC VN

Chuyn ngnh : Cng ngh thng tinM s : 1.01.10

LUN VN THC S

Ngi hng dn khoa hc:PGS.TS. Vc Thi

H Ni 2004


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3

Mc lc

BNG THUT NGV CC CHVIT TT .........................................................4LI CM N ..................................................................................................................5MU..........................................................................................................................7CH NG 1 ...................................................................................................................10GII THIU CHUNG V C S DLIU A PHNG TIN............................10

1.1 Cc kiu truyn thng va multimedia .............................................................111.1.1. Csd liu v cc DBMS ....................................................................121.1.2. Truy tm thng tin ti liu vn bn ..........................................................121.1.3. Truy xut v ch s ho multimedia.........................................................131.1.4. Trch rt c trng, biu din ni dung v ch s ho .............................13

1.2 S cn thit i vi MIRS...............................................................................13

1.2.1. S pht trin v d liu multimedia v cc c trng ca n..................141.2.2. Cc DBMS v vai tr ca chng trong vic x l d liu multimedia....151.2.3. H thng IR v vai tr ca n trong vic truy xut multimedia ..............181.2.4. Cch tip cn tch h p vic truy xut v ch s ho thng tin multimedia

191.3 Tng quan v MIRS ........................................................................................191.4 Cc ng dng ni chung v kh nng mong i ca MIRS...........................20

CH NG 2 ...................................................................................................................24C S DLIU A PHNG TI N (Multimedia Database)................................24

2.1 Kin trc cho vic t chc ni dung................................................................25

2.4.1 Nguyn l t tr ........................................................................................252.4.2 Nguyn l ng nht................................................................................262.4.3 Nguyn l lai ghp...................................................................................27

2.2 T chc d liu multimedia da trn nguyn l ng nht. ..........................302.3 Cu trc tm tt media ....................................................................................32

2.4.1 D liu nh nh l mt tm tt media. ....................................................332.4.2 D liu video nh l mt tm tt media. .................................................342.4.3 nh ngha v mt CSDL Multimedia n gin ......................................362.4.4 nh ngha v mt CSDL Multimedia c cu trc ..................................37

2.4 Ngn ng truy vn khai thc d liu multimedia............................................39

2.4.1 Truy vn SMDSs (m tng nht)........................................................40 2.4.2 Truy vn d liu multimedia m t di kin trc lai to.......................432.4.3 Ch s ho SMDS vi ch so.............................................................46

CH NG 3 ...................................................................................................................52H QUN TR C S DLIU A PHONG TIN YU CU V CC VN...................................................................................................................................52

3.1 Mc ch ca MDBMS ...................................................................................52


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3.2 Cc yu cu ca mt MDBMS........................................................................553.2.1 Kh nng qun tr lu tr ln...................................................................573.2.2 H trtruy vn v khai thcd liu. ........................................................58

3.2.3 Tch hp cc phng tin, tng hp v th hin......................................593.2.4 Giao din v tng tc.............................................................................593.2.5 Hiu sut. .................................................................................................60

3.3 Cc vn ca MDBMS.................................................................................603.3.1 M hnh ho d liu MULTIMEDIA......................................................603.3.2 Lu tri tng MULTIMEDIA..........................................................623.3.3 Tch hp multimedia, th hin v cht lng ca dch v (QoS)............633.3.4 Ch s ho multimedia .............................................................................643.3.5 H trtruy vn multimedia, khai thc v duyt qua................................653.3.6 Qun tr CSDL multimedia phn tn .......................................................66

3.3.7 S h trca h thng .............................................................................67CH NG 4 ...................................................................................................................69XY DNG H THNG MUA BN HNG QUA MNG......................................69

4.2.1. Gii thiu.....................................................................................................694.2.2. ng dng CSDL a phng tin vo h thng bn hng qua mng...........70

4.2.1. Xy dng kho d liu hnh nh 2D v 3D...............................................714.2.2. Xy dng cch truy vn i vi kho d liu hnh nh .........................71

4.2.3. H thng bn hng qua mng ......................................................................734.3.1. M hnh h thng.....................................................................................73 4.3.2. Cc chc nng cbn ca h thng.........................................................754.3.3. Cc cng c pht trin h thng...............................................................764.3.4. Quy trnh thc hin giao dch ca h thng.............................................77 4.3.5. Ci t h thng .......................................................................................78

4.4. Gii php tch hp cc h thng khc .............................................................804.4.1. H thng qun l v cp pht chng ch s (CA)....................................80 4.4.2. H thng thanh ton trc tuyn (VASC Payment) ..................................81

4.5. Mt s giao din chnh ca h thng...............................................................83KT LUN....................................................................................................................86TI LIU THAM KHO..............................................................................................87

BNG THUT NG V CC CH VIT TT


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STT K hiu vit tt Gii thch1 Web browser Trnh duyt Web2 CSDL Csd liu

3 DBMS H qun tr csd liu4 MDBMS H qun tr csd liu a phng tin5 Video frame Khung hnh video6 RDBMS H qun tr csd liu quan h7 Multimedia a phng tin8 MIRS H thng truy vn thng tin a phng tin9 Metadata Siu d liu

10 Media Phng tin11 SMDS H thng csd liu a phng tin c cu trc12 Information Retrival(IR) Truy xut thng tin

13 Multimedia InformationRetrieval System (MIRS)

H thng truy xut thng tin a phng tin

LI CM N


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Ti xin by t lng knh trng v bit n su sc ti PGS.TS Vc Thi, ngi thy,

ngi ng nghip trc tip hng dn, cho ti nhng nh hng v nhng kin

rt qu bu v csd liu a phng tin. Ti cng xin chn thnh cm n cc ngnghip ca ti ti phng Cc h thng qun tr d liu Vin Cng ngh thng tin

gip ti rt nhiu trong qu trnh cng tc ti c th hon thnh bn lun vn ny

mt cch tt p

Xin chn thnh cm n cc bn b ca ti, trong nc cng nh ngoi nc gip

ti rt nhiu trong qu trnh tm ti v su tm ti liu.

Cui cng xin chm thnh cm n cc thnh vin trong gia nh ng vin v to

mi iu kin thun li ti c c kt qu nh ngy hm nay.

H ni ngy 20/06/2004

Hc vin

Trn Hoi Nam


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MU

Cng ngh multimedia lin quan ti vic m t s kt hp cc dng thc thng tin

khc nhau (vn bn, d liu, hnh nh, m thanh, video) di dng tn hiu s. C th

nu ra y mt sng dng multimedia nh :

E-learning.

Hi tho Video (Video Conferencing).

Th vin in t (Elibrary).

Hin ti o (Vitual Reality).

Cc cng ngh truyn dng thao tc, truyn pht, iu khin cc d liu multimedia

v ang c nghin cu mt cch rt si ng.

Cc h thng multimedia cn c mt h thng phn phi nhm mc ch thu thp cc

i tng multimedia v a chng n ngi dng, mt trong s cc phng tin u

tin c dng dn l a t v a quang. Ngy nay, Internet cng nh cc giao thc

khc nh TCP/IP, NetBIOS, cc mng Lan ang tr thnh cc phng tin truyn

b d liu multimedia . Kh nng m t phong ph cng nh kh nng ha ca cc

web browser cng vi cc tnh nng ang c tip tc tng cng nh hot ha, mthanh v Video khin cc web browserang tr thnh mt phng tin mi mang

li cc d liu multimedia cho ngi dng[5]

Cc cng ngh ch yu lin quan n multimedia bao gm:

K thut nn.

Video Servers.

Cc k thut v mng (internet, tokenring, ethernet, ATM vv).

Cc cng ngh truyn d liu.

Cc cng ngh v cp truyn dn.

Cng ngh xc thc.

Cc cng ngh v CSDL.


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Mt CSDL l tp hp ca cc d liu c lin quan n nhau. Mt h qun tr CSDL

(DBMS) l h thng phn mm trgip cho cc qu trnh khai bo, xy dng v thao

tc vi CSDL phc v cho cc ng dng khc nhau. CSDL multimedia bao gm thmcc kiu d liu khc nh:

Vn bn.

Hnh nh.

m thanh.

Video.

Hot hnh.

Cc kiu d liu khc ny i hi phi c cc phng thc c bit nhm mc ch ti

u ha cho vic lu tr, truy cp, ch s ho v khai thc. Mt MDBMS phi cung cp

mt mi trng thch hp qun l v s dng CSDL multimedia.

Mt MDBMS cn phi m bo cc tnh nng cbn ca mt DBMS, ngoi ra n cn

phi c cc tnh nng khc nh:

Tch hp cc phng tin khc (Media Intergration).

Kh nng sp xp v m t thng tin.

Kh nng khai thc d liu..

Kh nng lu tr ln.

Giao din multimedia.

H trtruy vn tng tc multimedia.

Thng thng cc i tng ring l ca mt hnh nh hoc mt video frame s c mt

vi mi lin h b phn vi cc i tng khc. Cc mi lin h ny a n mt s

cc rng buc trong qu trnh tm kim cc i tng trong CSDL multimedia. Cn ctrn csny vic trin khai cc ng dng multimedia trn nn cc h qun tr CSDL

hng i tng s thun li hn so vi cc RDMBS hin thi[1].


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Mc tiu chnh ca bn lun vn ny nhm nghin cu v tm hiu mt s vn n c

bn ca mt MDBMS:

Tng quan v cs d liu a phng tin Cc yu cu ca mt MDBMS cng nh kin trc, thit k v truy vn i vi

mt MDBMS.

Lun vn ny c b cc thnh 5 phn chnh:

Chng I: Gii thiu chung v CSDL multimedia.

Chng II: Csd liu multimedia.

Chng III: H qun tr csd liu multimedia Yu cu v cc vn

Chng IV: Xy dng h thng bn hng qua mng.

Kt lun


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CHNG 1

GII THIU CHUNG V C S D LIU A PHNG TIND liu multimedia c chia thnh hai lp l cc d liu lin tc v cc d liu khng

lin tc. Cc d liu lin tc bao gm cc d liu m thanh, video thay i theo thi

gian. Cc d liu khng lin tc l cc d liu khng phc thuc vo thi gian, cc loi

d liu c trng cho dng ny l cc d liu vn bn (c hoc khng c nh dng),

hnh nh tnh v cc i tng ha. Cc kiu d liu thng thng ca mt CSDL

multimedia bao gm:

D liu vn bn (c hoc khng c nh dng).

ha: l cc bn v, minh ha c m ha nh cc tp postscript.

Hnh nh: l cc hnh nh c m ha s dng cc dng thc chun nh l

JPEG hoc MPEG.

Cc hot hnh.

m thanh.

Video.Cc c tnh chung ca d liu multimedia bao gm:

Thiu cu trc: Cc d liu multimedia c khuynh hng phi cu trc v vy

cc tc nghip qun tr d liu chun nh ch s ho, tm kim ni dung, truy

vn d liu thng l khng p dng c.

Tnh tm thi: Mt vi kiu d liu multimedia nh l Video, m thanh v hot

hnh u ph thuc vo yu t thi gian lin quan mt thit n vic lu tr,

thao tc v m t chng. C dung lng ln: cc d liu video v m thanh thng i hi cc thit b

lu tr ln.


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Cc ng dng h tr: cc d liu phi chun c th i hi cc quy trnh x l

phc t p nh vic s dng cc thut ton nn d liu i vi cc ng dng

CSDL multimedia.

1.1 Cc kiu truyn thng v multimedia

Truyn thng cp n cc kiu thng tin hoc cc kiu biu din thng tin, v d

nh d liu vn ch ci, hnh nh, m thanh, truyn hnh. C nhiu cch phn lp

truyn thng. Nhng cch phn loi chung c da trn nhng dng vt l v nhng

mi quan h truyn thng vi thi gian. Ta phn lp truyn thng da trn vic c hay

khng c chiu thi gian. Ngm nh ny hng ti hai lp truyn thng tnh v ng(hoc tnh lin tc v thi gian).

Truyn thng tnh khng bao hm yu t thi gian, cc ni dung v ngha ca chng

khng ph thuc vo thi gian c biu din. Truyn thng tnh bao gm cc d liu

vn ch ci, cc th v cc nh tnh.

Truyn thng ng bao hm yu t thi gian, cc ngha v tnh chnh xc ca chng

ph thuc vo loi c biu din. Truyn thng ng gm cc hot hnh, m thanh v

video. Cc truyn thng ny c bn cht khong thng nht hoc tc ring cachng. Chng hn, truyn cm gic chuyn ng nhp nhng video phi thc hin

25 hnh mi giy (hoc 30 hnh ph thuc vo h thng video ang s dng). Tng

t, khi chng ta pht li mt li nhn hoc on nhc c ghi m, ch c mt loi

th hin l thch h p. Vic pht li ch nhanh hn hoc chm hn s lm mo

ngha hoc cht lng m thanh. V nhng truyn thng ny phi c pht lin tc

tc cnh m chng thng c gi l truyn thng lin tc. Chng cng cn

c gi truyn thng ng thi v mi quan h cnh gia mi n v truyn thng

v thi gian.

Truyn thng cp n mt b su tp cc kiu truyn thng s dng cng nhau.

iu c ngha l t nht c kiu truyn thng d liu l khng theo k t ch (ngha


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l t nht c mt kiu truyn thng l nh, m thanh hoc truyn hnh). y,

multimedia c s dng nh mt tnh t v vy chng ta s ni mt cch c trng

l thng tin multimedia, d liu multimedia, h thng multimedia, lin lc multimedia,ng dng multimedia,... D liu multimedia chnh l s biu din v cc loi truyn

thng multimedia m my tnh c thc c. Thng tin multimedia l thng tin

truyn bng cc kiu truyn thng multimedia. i khi, thng tin multimedia v d

liu multimedia c s dng c th thay cho nhau.

i khi chng ta s dng thut ng multimedia hay truyn thng v i tng nhm

ch mt thc th t tr no trong mt MIRS m c thc truy vn, truy xut v

c trnh din. Thut ng i tng c th l cha xc nh thch hp theo nghahng i tng (0bject Oriented). Ng cnh s lm n r rng hn d cho n c s

dng trong mt ngha chung hoc trong cch tip cn hng i tng[10].

1.1.1. C s d liu v cc DBMS

Trong th vin, CSDL v cc DBMS i khi c s dng thay th nhau. y CSDL

hiu nh mt b su tp hoc mt kho d liu hoc nhiu mc truyn thng. Chng ta

s dng cc DBMS nh mt h thng thc th qun l CSDL.

1.1.2. Truy tm thng tin ti liu vn bn

H thng truy tm thng tin tng ho (IR) c pht trin gip qun l mt khi

lng vi cc ti liu khoa hc c to lp t nhng nm 1940. Chc nng chnh

ca mt h thng IR l lu tr v qun l mt s rt ln cc ti liu vn bn theo cch

sao cho cc ti liu thch hp vi vic s dng cc truy vn truy tm nhanh. Ch

rng vic truy tm thng tin tng ca cc t cu to bng chu ca nhng t khcl nhm vo vic truy tm cc ti liu vn bn, mc d thut ngy l truy tm

thng tin c th hiu l truy tm mt loi thng tin no .


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1.1.3. Truy xut v ch s ho multimedia

Cc DBMS truy xut cc khon mc da trn s liu c cu trc khi s dng kt ni

chnh xc. IR cng c gi l truy xut da trn vn bn. Vic truy xut da vo nidung cp n vic truy xut da trn nhng nt c trng truyn thng hin nay nh

l mu sc, hinh th thay cho li gii thch vn bn v khon mc truyn thng .

Vic truy xut da trn ni dung l chun da trn sng dng thay v mt kt ni

chnh xc gia mt truy vn v mt tp cc khon mc d liu.

MIRS cp n mt h thng cscung cp vic truy xut thng tin multimedia khi

s dng mt t hp DBMS, IR v cc k thut truy xut da trn ni dung. Trong mt

MIRS, mt vi vn nh phin bn v iu khin an ton c th khng thc hin

c y . Mt MIRS bn lnh ra i c gi l MDBMS.

1.1.4. Trch rt c trng, biu din ni dung v ch s ho

Trong cc MIRS, mt trong nhng vn quan trng nht l trch rt c trng hoc

biu din n i dung (ci g l nhng nt c trng hoc ni dung chnh trong mt khon

mc multimedia). Trch rt c trng c th l qu trnh tng hay bn tng.

Trong mt vi ti liu truy xut da vo ni dung, trch rt c trng cng c gi lch s ho. Sau y, chng ta theo quy c chung. Khi m thut ng ch s c s

dng nh mt danh t, iu c ngha l cp ti cu trc d liu hoc vic t chc

nhng c trng c trch rt nghin cu c hiu qu v truy xut.

1.2 Scn thiti vi MIRS

S cn thit i vi MIRS c thc gii thch bng ba yu t sau:

Trc ht, d liu multimedia ang c dng ngy cng nhiu v ang c ch . s dng thng tin (cha trong d liu ), i hi c mt h thng truy xut v

ch s ho hiu qu v c hiu lc. Th hai, d liu multimedia c nhng c tnh v

nhng yu cu c bit m li khc nhau ng k t s liu bng ch ci. Bi vy,


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DBMS truyn thng khng thch hp cho vic x l d liu multimedia. Th ba, mc

d cc k thut IR c th gip chng ta trong vic truy xut multimedia nhng ch mt

mnh chng th cha x l d liu multimedia mt cch c hiu qu[10].

1.2.1. S pht trin v d liu multimedia v cc c trng ca n

Hin nay chng ta ang tp trung khai ph thng tin multimedia. V d, mt s lng

ln hnh nh v video ang c to lp v lu tr trn internet. Nhiu ho s v bc

tranh trong nhiu kiu in ra l ang c chuyn sang dng k thut s cho d x l,

phn phi v bo tn. Cc bc tranh t cc bn tin trn v tuyn v trn bo cng c

chuyn sang dng k thut s d bo tr v bo tn. Mt s ln cc hnh nh y tang c tp trung hng ngy v cc v tinh ang c sn xut nhiu hn. Khuynh

hng ny c nh tip tc nng cp vic lu tr v cc cng ngh k thut s. Vic

lp ra mt ch cha i vi lng ln thng tin multimedia ngy cng tng nh vy

cn c t s dng. iu ny s khng th s dng y thng tin multimedia ny

tr khi n c t chc truy xut nhanh theo yu cu.

Khng ch l ang tng v s lng d liu ang c lu tr, m cn c cc kiu d

liu v cc c trng ca chng l khc nhau t d liu k t ch.C nhng c trng chnh ca d liu multimedia nh sau:

D liu multimedia, nht l m thanh v video, l d liu c s lng ln. V

d, mt video 10 trung bnh chim 1,5 GB cha nn.

m thanh v video c chiu thi gian v chng khi biu din s chim t l c

nh hot ng c hiu qu nh yu cu

m thanh s, nh v video c trnh din theo mt lot gi trn c th v

thiu cu trc ng ngha r rng cho my tnh tng ho nhn bit ni dung

Nhiu ng dng multimedia i hi vic biu din ng thi cc kiu truyn

thng a nng theo cch kt hp khng gian v thi gian


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nghia ca d liu multimedia i khi rt mv c tnh ch quan. V d, mi

ngi c cch gii thch cng 1 bc tranh theo cch khc nhau hon ton ring

D liu multimedia l giu v thng tin, nhiu tham sc i hi mi trnhdin ni dung ca n.

1.2.2. Cc DBMS v vai tr ca chng trong vic x l d liu

multimedia

Cc DBMS ngy nay c xy dng kh tt v c s dng rng ri i vi d liu

c cu trc. Cc DBMS tri nht l cc h qun tr d liu quan h (RDBMS). Trong

RDBMS, thng tin dc t chc thnh bng hoc cc quan h. Cc dng ca bngtng ng vi cc khon mc thng tin hoc cc record, trong khi cc ct tng

ng vi cc thuc tnh. Ngn ng truy vn c cu trc (SQL) c s dng to ra

cc bng nh th v chn v truy xut thng tin t cc bng [11].

Chng ta dng mt v dn gin d minh ho cch s dng SQL to lp mt bng

v chn, truy xut thng tin t. Gi s chng ta mun lp mt bng cha cc bn

ghi v sinh vin bao gm s hiu sinh vin, tn v a ch. Ta c lnh sau:

Create table STUDENT(

stu# integer,

name char(20),

address char(100));

Khi chng ta mun chn cc bn ghi v sinh vin vo bng, chng ta s dng lnh chn

SQL nh sau:

Insert into STUDENT values(10,"Lew, Tom","2 Main St.,

Churchill, australia");

Lnh trn s chn mt dng vo bng STuDeNT


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Thng tin trong bng c truy xut khi s dng cu lnh SELECT ca SQL. V d,

nu mun truy xut tn ca sinh vin vi sinh vin s 32, ta s dng lnh truy vn sau:

Select Name

From STUDENT

Where Stu#=32

Cc thuc tnh trong RDBMS cnh kiu v rng. Trong v d trn, thuc tnh

Stu# la kiu integer vi di cnh l 32 bit. Nh vy, RDBMS l thch hp x

l d liu s v dng k t ngn.

h trcho cc trng c gi tr ln trong RDBMS, mt khi nim c gi l i

tng rng hoc nhi phn (BLOB) sc gii thiu. Mt BLOB l mt xu bit ln

cc di bin. V d, nu ta mun lu bc tranh ca sinh vin trong bn ghi bng

STUDENT trn, chng ta c th to ra mt bng khi s dng lnh sau:


Stu# integer,

Name char(20),

address char(100),

Picture BLOB);

Cc BLOB bnh thng ch l xu bit v hot ng bng vic so snh ch khng mang

chng ra ngoi. l v RDBMS khng bit ni dung hoc ng ngha ca mt BLOB.

Tt c BLOB hiu nh mt khi d liu.

Mt dng khc ca cc DBMS l h thng qun tr CSDL hng i tng(OODBMS). Cc OODBMS kt ni cc kh nng ca csd liu (nh lu tr v

tm kim) v cc c trng hng i tng (tm lc, s tha k, tnh ng nht i

tng). Mt phng php tip cn chung l kt ni cc c im hng i tng vi

csd liu quan h. H thng c kt ni th c gi l mt h thng csd


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liu i tng quan h. Trong mt h thng nh vy, cc i tng c xc nh mt

cch thch hp trong hng i tng. Trong mi i tng cha cc c tnh hoc

thuc tnh v cc phng php hoc cc hm c s dng ch tc ra cc c tnhkhc. V d, chng ta c th nh ngha mt loi nh sau:

Create type IMAGE(

Private

Size integer,

Resolution integer,

Content float[ ],

publlic

...

);

Sau khai bo cc tranh bi kiu IMAGE c thc s dng trong mt bng

nh sau:


Stu# integer,

Name char(20),

Address char(100)

Picture IMAGE);

im khc bit chnh gia BLOB v cc i tng l i tng th c nh r mt

cch thch ng, bao gm cc c tnh v cho php chng c tc dng, trong khi th

BLOB th khng.Cc khi nim v cc BLOB v cc i tng l mt bc gn vi x l d liu

multimedia . Nhng cc BLOB c s dng ch lu d liu c khi lng ln.

Trong khi cc i tng cha vi thuc tnh n gin, nhiu chc nng hn nn c


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pht trin x l vic truy xut multimedia da vo ni dung. Mt vi cc kh nng

c yu cu nh sau:

Cc cng c, tng ho hoc bn tng trch rt cc ni dung v cc ctrng trong d liu multimedia ;

Cc cu trc ch s ho a chiu, iu khin cc vector multimedia

Cc o tng ng, nhm truy xut multimedia thay v kt ni mt cch

chnh xc

Lu tr cc h thng ph, thit k li nhm p ng cc yu cu ca bng tn

cao vi cln, tho mn nhng i hi theo kiu thi gian thc

Giao din s dng, c thit k cho php cc cu hi a dng trong nhiu kiu

truyn thng a dng v cung cp cc trnh din multimedia

1.2.3. H thng IR v vai tr ca n trong vic truy xut multimedia

Ngoi cc DBMS, c loi h thng qun l thng tin khc tp trung vo vic truy xut

ti liu vn bn. Loi h thng ny c gi l h thng truy xut thng tin (IR).

K ngh IR kh quan trng trong h thng qun l thng tin multimedia v hai l do

chnh. Mt l chng tn ti mt lng ln cc vn bn trong nhiu dng t chc, v d

nh cc th vin. Vn bn l mt ngun thng tin quan trng trong bt k mt t chc

no. s dng cc thng tin c lu tr trong cc ti liu ny, cn c mt h

thng IR hiu qu. Hai l, vn bn c thc s dng ch gii cc truyn thng

khc nh m thanh, hnh nh, video. Thng thng th cc k ngh IR c th dc s

dng cho vic phuc hi thng tin a truyn thng. Tuy nhin, vic s dng ch x l

d liu truyn thng phi tun theo cc gii hn sau:

Vic ch gii nhn chung phi lm bng tay v tiu tn thi gian

Vn bn ch gii cha y v cn mang tnh ch quan

Cc k ngh IR khng thiu khin cc cu hi t vn bn khc (nh m

thanh v nh).


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Mt vi c tnh ca multimedia nh b cc hnh nh v cc dng i tng l

khc nhau, nu khng th cng ch l cng m t mt vn bn.

1.2.4. Cch tip cn tch hp vic truy xut v ch s ho thng tin

multimedia

T tho lun trn chng ta c th thy rng cc DBMS v IR khng thp ng y

cc yu cu v ch s ho va truy xut multimedia, v vy cn c cc cng ngh mi

vn dng nhng c trng ring ca multimedia... Tuy vy, vn nhn thy rng cc

DBMS v IR vn ng vai tr quan trng trong cc MDBMS. Cc phn ca d liu

multimedia nh ngy v tc gi to lp ca ti liu multimedia l c cu trc. D liuc kt cu ny c thc iu khin bng cc k ngh DBMS. Vn bn ch gii vn

l phng php hiu lc trong vic ghi li ni dung.

Tom li, mt cch tip cn tch hp t hp cc DBMS vi IR, v cc k thut c t

x l d liu multimedia c i hi pht trin MIRS hiu qu v c hiu lc.

1.3 Tng quan v MIRS

Cc mc thng tin trong csd liu c x l trc rt ra cc c trng vni dung ng ngha, c ch r da trn cc c trng v ng ngha ny. Trong sut

qu trnh phc hi thng tin, mt cu hi ca ngi s dng c x l v c im

chnh c rt ra. Cc c trng ny sau c chun b cng vi cc c trng hoc

ch th ca mi mc thng tin trong csd liu. Cc c trng ca mc thng tin l

hu ht u tng ng cc cu hi c gi ra trc ngi s dng


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20

Hnh 1.1 : M t mu truy xut thng tin tng qut

C rt nhiu n bn uc vit theo mu trn trn. V d, Cc mc thng tin c th

c kt ni bt k vi cc loi truyn thng. Lm th no rt ra c nhng c

trng t cc tin tc truyn thng ny? Phi lu v xy dng c cc c trng ny

nh th no vic truy tm c hiu qu? Phi o tng ng nh th no gia

hai tin tc truyn thng? Cn phi lm g giao din s dng c thm nhn c

nhng cu hi phc tp, ri rm, linh hot? Phi so snh nh nh th no v vic biu

din cc qu trnh truy tm gia cc MIRS khc nhau? Lm th no ap ng cc

yu cu tm thi trong sut qu trnh truyn v biu din d liu multimedia?

1.4 Ccng dng ni chung v kh nng mongi ca MIRS

MIRS c cho rng hiu qu v linh hot. Kh nng ca n c mimh ho trn cc

dng cu hi m chng c th h tr. Cc kiu cu hi mong i c dng sau:

Cu hi da trn metadata: y l cu hi ch ra nhng thuc tnh thng thng

ca cc mc csd liu nh tn tc gi v ngy to l p. M t V d l cu hi


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21

theo yu cu trn video (VOD) c th l lit k tn cc phim c sn xut

vo nm 1997. Loi ny c vn dng bng DBMS

Cc cu hi da trn ch gii: y l cu hi ch ra cc m t dng vn bntrong ni dung ca csd liu. Cc cu hi u trong t kho hoc tronng

phn vn bn min ph v vic truy tm da trn s tong ng gia cu hi va

phn ch gii. V d, cu hi c th l Ch ra phn on quay video khi din

vin nam ang p xe p. Loi cu hi ginh ny c ch gii thch ng

v x l bi k ngh IR

Cu hi da trn mu d liu hoc tnh nng: y l cu hi ch ra thng tin

dng thng k, nh: m thanh, mu, mn. Mt v d: Ch ra nh video vi

s phn b mu nh THIS tr li dang cu hi nay, thng tin lit k v mc

csd liu nn c su tp trc v lu tr

Cu hi v d

y l cu hi trong cc i tnga truyn thng nhhinh nh, phc tho, on m

thanh. V d: chra 1 b phim v cc cnh tng tnhBc tranh ny. Loi cu

hi ny c thb lm ri ln bi mi lin h vkhng gian v thi gian gia cc i

tng

Cc cu hi ng dng ring

Cc cu hi ng dng ring c rt nhiu loi. V d, cu hi da trn thng tin chi tit

v c th nh kch c1 i tng v qu trnh gi ho ca 1 ngi.

Cc MIRS c mong mi c tha ra nhiu loi cu hi khc nhau, do c ng

dng rng ri, bao gm:

Thuc. Mt bc sa ra nh chp sng siu m mi v mun tm li nh vi

mc c th so snh c ca s phnh tm tht tri t mt nh chp siu m

cs


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22

Bo mt. Mt cnh st a ra h thng vi mt bc tranh v mt ngi v mun

phc hi li nhng hnh nh khc vo h shin thi ca nhng ngi ging

vi bc tranh ny t csthng tin bo mt Gio dc. Mt sinh vin qut chp mt tranh ng vt v mun truy tm tt c

cc thng tin (bao gm m thanh, hnh nh, vn bn m t). Tip theo, mt sinh

vin khc thm m thanh cho con vt v mun khi phc li bc tranh v thng

tin m t loi ng vt ny

Bo ch. Mt bo co vin vit mt bai bo v mt ngi v mun truy tm bc

tranh ca ngi v cc thng tin tng hp xut hin trn cc bo v tivi

20 nm trc

Gii tr. Mt quan st vin mun truy tm mt oan bng tng t vi nhng g

m anh ta xem trn mt csd liu video ln hn

ng k nhn hiu. Mt cn b gia cng mt nhan hiu ng k no mun

quyt inh xem c mt cai nhn hiu no trc ging nh vy c

ng k cha. lm iu ny, anh ta cn mt csd liu v nhn hiu so

snh cc nhn hiu ging nhau nht hin c lm ra mt nhn hiu hon ton

mi

Cui cng, cc MIRS s tp trung vo chnh thng tin thay th cc loi truyn thng

v vic miu t chng c thc sp xp hoc dch ra t loi truyn thng ny n

loi truyn thng khc. V d, mt video tai liu cn phi c s dng video, hnh

nh, vn t, m thanh, li ni v nhng th tng t nh vy. V vy phng tin d

tm phi kt ni cc cu hi (d liu) vi cc mc csd liu.

Cc loi truyn thng khc nhau cn cc k ngh phc hi v cch biu th khc nhau.Cc k ngh khc nhau c s dng cho tng loi truyn thng khc nhau. Ngi s

dng c th thy thch nhng thng tin xc ng m bt chp s khc nhau v cc

loi truyn thng. Vn l lm th no tch hp c cc loi k ngh khc nhau

tuy tm thng tin cn tm trong vic tr li cc cu hi ca ngi s dng. C rt


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23

nhiu cc n phm c vit gii quyt vn ny, nh ghi r cu hi v x l,

khon ph cp thm tng xng, ghp cc miu ti tng.

vic truy tm c hiu qu, cn c mt cu trc cc khon mc hp l. Bi v ccvectorc tnh u a dng v kch c v vic truy tm cc khon mc trong cc

MIRS da trn s tng ng thay cho vic kt ni chnh xc, cu trc mc lc c

s dung trong cc DBMS khng thch hp vi cc MIRS.

Khuynh hng ca cc yu cu bao gm h s tr v git, gi l cht lng dch

v (QoS), cn c trong vic truyn v m t d liu truyn thng.

Trong cc DBMS, tin hnh chnh lin quan n hiu qu (thi gian tr li cu hi).

N rt quan trng bi kch cln ca multimedia. Ngoi ra, hiu qu truy tm cng rtquan trng (kh nng truy tm cc mc thch hp v kh nng loi b cc mc khng

cn n). Bi cc MIRS truy tm cc mc chn da trn cs o s tng ng, s

dng lut tng ng thay th cho kt ni chnh xc. Tr khi n trnn qu kh i vi

vic thit k cc o tng ng th cn xc nh mt cach chnh xc bng c phn

on ca con ngi, ging nh mt vi khon mc c h thng xc nh l thch hp

nhng ngi dng li cho l khng thich hp v mt s mc thch hp li khng c

truy xut.


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CHNG 2

C S D LIU A PHNG TIN (Multimedia Database)Khi thit k mt h thng CSDL multimedia m t cc loi d liu multimedia khc

nhau, chng ta bt buc phi i din vi mt s cu hi quan trng c t ra v

cch thc t chc h trng nh:

Vic t chc v mt ni dung i vi d liu ca cc loi d liu

multimedia.

Vic lu tr vt l ca cc d liu ny trn cc thit b lu tr nh th

no.

tr li cho cc cu hi ny, trc tin chng ta xem xt ti kha cnh t chc ni

dung


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2.1 Kin trc cho vic t chc ni dung

y chng ta xem xt ti 3 kin trc p dng cho vic t chc ni dung ca mt h

thng CSDL multimedia

2.4.1 Nguyn l t tr

Nguyn l ny cp ti vic chng ta nhm tt c cc d liu nh, d liu video v tt

c cc d liu vn bn v ch s ha chng theo nguyn tc ti a ha hiu sut ca tt

c cc loi truy nhp i vi cc loi d liu m chng ta dnh. Nguyn l ny m

bo rng vi mi loi d liu (nh, video, vn bn) chng u c t chc vi mt

cch thc c trng ph hp vi mi loi d liu ny[18].

Hnh 2.1: M t nguyn l ttr


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2.4.2 Nguyn l ng nht

Mt nguyn l kin trc khc m chng ta c th la chn l nguyn l ng nht,

nguyn l ny gip chng ta tm c mt cu trc tm tt chung cho tt c cc loi dliu. Cu trc ny c thc dng trong vic ch s ha tt c cc loi d liu qua

to ra mt ch s thng nht m chng ta c th dng truy cp ti cc i tng

khc nhau. Hay ni mt cch khc l chng ta c th trnh by tt c cc i tng

khc nhau( nh, video, m thanh, vn bn) trong mt cu trc d liu duy nht v qua

pht trin cc thut ton truy vn cu trc d liu ny[18].

Hnh 2.2: M t nguyn l ng nht


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2.4.3 Nguyn l lai ghp

tng ca nguyn l ny l da trn s kt hp ca 2 nguyn l trnh by trn.

Kt qu ca nguyn l ny l mt kiu d liu no s dng ch s (index) ring cachng, trong khi cc kiu d liu khc s s dng mt ch s (Index) thng nht.

Loi d liu no s dng kiu ch s no s ph thuc vo cc c tnh khc nhau s

c ni n phn sau[18].

Hnh 2.3: M t nguyn l lai ghp

C ba loi nguyn l trn u c nhng u im v nhc im ring ca mnh. Kin

trc da trn nguyn l t tri hi vic to ra cc thut ton v cu trc d liu ca

mi kiu d liu, ngoi ra n cng i hi cc k thut h trcho vic lin kt cho

gia cc cu trc d liu khc nhau ny. Cc cng vic ny i hi tnh phc tp cao

v i hi mt lng thi gian ln cho vic pht trin. Bn cnh cc nhc im trn,

vic xy dng cc cu trc c c bit ha ti u cho vic truy xut dn tng loi d


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liu khc nhau, CSDL multimedia c t chc theo nguyn l ny thng em li

hiu qu cao trong vic x l tm kim. i vi cc ngn hng d liu c xy

dng sn, ni m cc thut ton v cc cu trc d liu c s dng c hiu qu thvic p dng nguyn l t tr l m hnh kin trc thch hp nht. Cc k thut hng

i tng chnh l cng cc lc nht h trcho vic trin khai theo nguyn l ny

bng cch xem mi loi d liu ngun l mt i tng m cc phng thc ca n c

th truy cp c t mt CSDL multimedia tng th.

Tri ngc vi nguyn l t tr, nguyn l ng nht i hi chng ta phi tm ra c

mt cu trc d liu chung m c th dng lu tr cc thng tin v ni dung ca

hnh nh, video, vn bn, m thanh v cc loi d liu khc. iu ny i hi chng taphi phn tch ni dung ca mi kiu d liu v tm tt c phn chung ca chng,

qua xy dng mt b ch s da trn cc yu t chung c xc nh ny. u

im ni bt ca nguyn l ng nht l d dng trin khai v cc thut ton thng

c thc hin rt nhanh. Nhc im chnh ca nguyn l ny l cc s ch gii phi

c to ra theo mt cch ring no , thng l c to ra mt cch th cng hoc

l tng, vic to ra cc ch gii mt cch th cng thng i hi nhiu v mt thi

gian cng nh chi ph, mt khc trong qu trnh to cc ch gii ny thng sy ra s

mt mt thng tin nu ngn ng dng ch gii khng trnh by ht c cc kha

cnh ca ni dung. C tha ra y mt s v d nh ngn ng ch gii ni dung ca

hnh nh c th lm mt cc thng tin v b mt ca mt im nh (pixel) hoc mt

nhm im nh. Tng t nh vy ngn ng ch gii ni dung ca m thanh c th

lm mt cc thng tin v bin , tn s ca tn hiu ti mt thi im no .

Nguyn l lai to tp hp c cc u im ca c hai nguyn l nu trn, ng thi

gim thiu c mt s cc nhc im ca chng. Gi s chng ta mun to ra mt

CSDL multimedia bao gm cc kiu d liu M1,.,Mn, chng ta bt u bng vic

phn chia tp ny thnh 2 phn:


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Phn 1: bao gm cc loi d liu k tha t cc ngun d liu c sn, tn ti sn

cc ch s v cc thut ton thao tc vi ch s. Vi vic b tr ny chng ta

tn dng c li th ca cc ch s v m ngun sn c. Phn 2: bao gm cc d liu khng c k tha t bt k ngun no v do

khng c sn cc ch s ca mnh (iu ny ng ngha vi vic l cng khng

c bt k thut ton no c th thao tc vi tp ch s). Trong trng hp ny

vic tip cn xy dng h thng theo nguyn l ng nht l cch thc thch hp

nht ngay c khi l cch tip cn ny c th ny sinh ra vic gy mt mt cc

thng tin vt l chi tit.

Sau khi tin hnh xong vic phn chia, chng ta bt u tin hnh vic xy dng cc

thut ton cn thit kt hp cc ngun d liu khc nhau li bng vic s dng cc

tp ch s ring ca chng. Cch tip cn ny gip chng ta tha kc ti a cc ti

nguyn c sn, ng thi gim thiu c cc cng vic phi thc hin thm bi v cc

tp ch s ring c sn i vi mi loi d liu c tn dng. Gi s, mt ngi

dng mun a ra mt cu hi Hy tm tt c cc hnh nh v cc an video m

trong ng ch ca di tng A c mt v trao i vi i tng B. Cu hi ny

bao gm mt s kt hp gia cc tp ch s ca cc loi d liu khc nhau, chng s

truy cp n CSDL hnh nh (thng qua tp ch s ca d liu hnh nh), n CSDL m

thanh (thng qua tp ch s m thanh) v n mt CSDL quan h (thng qua tp ch s

quan h), cu hi ny c thc din t nh sau:

SELECT Name, Image, Audio

From Employee E, Image I, Audio A

Where E.Name= A AND

I contains E.boss andA contains E.boss AND

A CONTAINS B


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2.2 T chc dliu multimedia da trn nguyn lng nht.

Xt v d sau:

Bc nh photo1.gif c s xut hin ca i tng A, i tng B v mt i

tng cha c xc nh c chp ti thnh ph C thuc nc D vo ngy

10/01/1990.

on video video1.mpg c hnh nh ca i tng A a cho i tng B mt

chic vali (trong frames 50-100). on video ny thu c t s theo di nh

ca i tng B ti thnh ph E thuc nc F vo thng 1- 1991.

Vn bn B.txt c cha cc thng tin chi tit v di tng B c thu thp t d

liu ca cquan an ninh.

Bn thn mi i tng trn cng ni ln phn no ni dung ca tng i tng c

th (hnh nh, video, vn bn), tuy nhin thng tin a ra y ch ni ln ni dung v

mt ng ngha hn l cp n cc tnh cht c th ca mi loi i tng, cc tnh

cht loi ny c gi l cc c trng bc thp (lower-level). Mt cch tip cn hiu

qu nht i vi CSDL multimedia v c s dng rng ri trong thc t l s

dng cc i tng c pht biu trn nh l siu d liu (metadata).

Theo trn, gi s chng ta c mt tp cc i tng media o1,..,on chng ta kt hp

mt vi metadata md(o1) vi mi i tng media o1 (nh dng chnh xc ca

metadata ny sc trnh by sau), tng t nh vy cc metadata kt hp vi cc

i tng media 01,.0n tng ng s l md(o1),,md(on), Chng ta s tin hnh

vic ch s ha cc metadata ny vi mt cch thc nhm cung cp cc phng thc

trin khai hiu qui vi cc yu cu truy cp t pha ngi dng.

C th r rng thy rng, s thnh cng ca phng php ny ph thuc cbn vovic chng ta m bo c rng vi mi i tng media 0i th metadata tng ng

ca n md(oi) l c ng v phn nh ng ch nhng g m ngi dng yu cu[18].

Vi mt s lng ti thiu cc metadata c dng r rng l chng ta s d dng hn

trong vic ch s ha cng nh l thc hin cc thao tc khai thc d liu, tuy nhin


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bn cnh nu s lng metadata s dng t th c th ngi s dng s phi mt thi

gian hn trong vic thit lp cc cu hi ca mnh. C th ly trng hp sau lm v

d: Ngi dng: hy tm cho ti tt c cc on video hoc nh chp m i tng

A v i tng B (xem phn trn) trao i vi nhau mt gi hnh l.

H thng: Khng tm c (mc d h thng c on video ghi li i tng

A v i tng B trao i vi nhau mt chic vali nhng h thng vn tr li l

khng tm thy v n khng hiu rng mt chic vali cng c th coi l mt gi

hnh l).

Ngi dng: hy tm cho ti tt c cc on video hoc nh chp m i tng

A v i tng B (xem phn trn) trao i vi nhau mt vt g .

H thng: tm thy. frames 50-100 ca on video video1.mpg tha mn yu

cu ca bn.

Mc d c mt vi nhc im nh s dng metadata khng biu din ht c cc

kha cnh ca i tng media trong CSDL nhng cch tip cn da trn nguyn l

ng nht c mt su im ni tri sau:

Metadata thng c lu tr di dng cc cu trc c lin quan n tnh cht

quan h hoc hng i tng v c th truy vn mt cch d dng thng qua

vic mrng cc ngn ng (chng hn nh SQL).

Vic vit m thao tc vi metadata thng l d dng.

Vic vit cc chng trnh to ra metadata l n gin i vi cc lp trnh

vin c nng lc

Chng ta xem xt n ni dung ca d liu media di cc dng khc nhau, mt cuhi t ra y l u l phn chung nht ca cc loi d liu ny? Mc ch ca

chng ta l tm kim mt cu trc chung nht cho tt c cc loi d liu m qua n ta

c th th hin c ni dung ca cc loi d liu . Tm tt media l mt cu trc


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ton hc cho php din t ni dung ca cc media ny, s tm tt media c thc

trin khai thng qua mt cu trc d liu duy nht.

2.3 Cu trc tm tt media

Cu trc media tm tt c nh ngha nh sau:

Mt cu trc media tm tt l mt tp gm 8 tuple (S, fe, ATTR, , R,F, Var1, Var2)

Trong

S l mt tp cc i tng gi l cc trng thi.

Fe l mt tp cc i tng gi l cc c trng.

ATTR l mt tp cc i tng gi l cc gi tr thuc tnh. : S--> 2fe l mt nh x t cc trng thi sang tp cc c trng.

R l mt tp cc quan h trn fei x ATTRj x S vi i,j 0.

Fl mt tp cc quan h ca S.

Var1 l mt tp cc i tng gi l cc bin, thuc S

Var2 l mt tp cc bin, thuc fe.

Mt trng thi l on (chunk) nh nht ca d liu media m ta mong mun.

V d nh trong mt CSDL hnh nh, mi nh c thc xem nh l mt

trng thi. Nu quan im ny c chp nhn, chng ta s coi nh tt c cc

nh nh l cc i tng n l cbn v tt c cc c tnh ca n sc

quan tm v khi chng ta s khng quan tm n cc c tnh n l nh l

cc c tnh ca tng im nh. Trong trng hp d liu video, mt trng

thi c thc xem l mt chui lin ti p cc frame c dng (10 x i, 10 x

(i+1)) th hin mt on gm 10 frame bt u t frame c s th t chia ht

cho 10.

Mt c trng l bt ki tng no trong mt trng thi m n sc quan

tm. Mt c trng c th gao gm c cc i tng v cc phm vi ca n.

V d nh chng ta xem xt mt bc nh gm 3 i tng A, B v mt i


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tng cha c nhn bit th cc c trng c quan tm n y l A, B

v i tng C no . Tng t nh vy nu chng ta phn tch on video

t frame 50-100 th cc c trng c quan tm y l A, B v ci vali.Cc c trng xut hin trong mt trng thi c th c cc thuc tnh ca

mnh, v d nhi tng A bc ra khi chic xe t ca mnh th cc thuc

tnh ca chic xe t (loi xe, mu sc, bin s) cng cn phi c ghi nhn.

Tng t nh vy, mt i tng media cng c th c mt vi thuc tnh cn

c quan tm nh ngy, thi gian v a im chp bc nh .

l mt nh xc trng rt gn cho php ta bit c trng no xut hin

trong nhng trng thi no. c th l mt GUI cho php ngi s dng

tng tc nhm mc ch nhn bit c ni dung ca mt i tng media.

R l mt tp cc quan h trn fei x ATTRj x S cc quan h ny ph thuc vo

trng thi. V d nu xem xt mt bc nh nh photo1.gif th y c th c

mt quan h ph thuc vo trng thi gi l left.of bao gm mt b ba c dng

(i tng A, i tng B, photo1.gif). tng t nh vy chng ta cng c th

c mt quan h khc gi l background bao gm mt cp c dng (photo1.gif,

White_House).

Fc th cha cc lin kt kt hp 2 trng thi chng hn nh lin kt c trc,

nu chng ta c 2 bc nh (photo1.gif, photo2.gif) m gia chng tn ti lin

kt c trc th khi c ngha l bc nh 1 c chp trc bc nh 2 v

tip tc nh vy[18].

nm r hn, chng ta xem xt mt s v d p dng trn mt s loi i tng

media sau

2.4.1 D liu nh nh l mt tm tt media.

Gi s chng ta xem mt CSDL hnh nh n gin gm c 7 bc nh, CSDL ny s

tng ng vi media tru tng sau:


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Tp cc trng thi bao gm (pic1.gif,.,pic7.gif).

Tp cc c trng bao gm tn ca cc i tng xut hin trong cc bc nh

tng ng l Bob, Jim, Bill, Charlic v Ed. nh x thu gn cho chng ta bit vi mi trng thi c nhng c trng no

xut hin trong n. Bng sau s m t cho vn ny

Trng thi c trng

Pic1.gif Bob.Jim

Pic2.gif Jim

Pic3.gif Bob

Pic4.gif Bill

Pic5.gif Charlie

Pic6.gif Ed, Bill

Pic7.gif Ed

Bng 2.1: Lin h gia c trng v trng thi cho hnh nh

Mt im cn ch y l chng ta dng bng trn m t cho nhng cch thc

ch s ho m chng ta s dng c th khc i.

Tp cc quan h ch cha 2 quan h: mt quan h ph thuc vo trng thi gi l

left_of v mt quan h khng ph thuc vo trng thi gi l father.

Tp cc quan h ni ti c th trng

2.4.2 D liu video nh l mt tm tt media.

Tp cc trng thi bao gm 5 frames video t frame 1 n frame 5.

T p cc c trng bao gm Jane Shady, Denis Dopeman, ngi nh ca

Dopeman v chic valy.


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nh x rt gn c m tbng sau

State Feature

Frame1 Dopemanhouse,briefcase,JaneShady

Frame2 Dopemanhouse,briefcase,JaneShady,DenisDopeman

Frame3 Dopemanhouse,briefcase,JaneShady,DenisDopeman

Frame4 Dopemanhouse_briefcase,JaneShady,DenisDopeman

Frame5 Dopemanhouse,JaneShady

Bng 2.2: Lin h gia c trng v trng thi cho video

Cng ging nh trng hp p dng i vi CSDL hnh nh, nh dng c th

ca nh x c th khc i ti u ho cho qu trnh ch s ho v khai thc.

Chng ta c th c mt s quan h ph thuc vo trng thi sau:

o Quan h c (have) l mt quan h ph thuc vo trng thi xc nh

chic valy (i tng) xut hin cng vi nhn vt no trong trng

thi no? Quan h ny c c m t nh sau:

Person Object State

JaneShady Briefcase 1

JaneShady briefcase 2

JaneShady briefcase 3

DenisDopeman briefcase 4

Bng 2.3: Quan h Have

o Quan h vchng (spouse) l mt quan h ph thuc vo trng thi

ch ra tn v(hoc chng) ca mt i tng no . Quan h ny c

thc m t nh sau


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Person Spouse

JaneShady PeterShadyJaneShady PeterShady

DenisDopeman DebraDopewoman

Bng 2.4: Quan h v- chng

y c th ch c mt quan h ni ti ca trng thi gi l before (s1,s2)

ch ra rng trng thi s1 c trc trng thi s2.Cng tng t nh trn, chng ta c th d dng thy rng cc kiu media khc nhau

chng hn nh d liu m thanh hoc d liu vn bn c thc m t nh l mt

trng hp ca kiu media tm tt tng qut. Vi cu trc n gin cp trn, mt

CSDL Multimedia l mt tp bao gm cc media tm tt.

2.4.3 nh ngha v mt CSDL Multimedia n gin

Mt CSDL Multimedia n gin l mt tp hu hn Mca cc media tm tt.V d, mt CSDL Multimedia n gin c th cha tp vidoe video1.mpg v mt tp

nh photo1.gif, trong trng hp ny CSDL c cha hai trng hp ca media tm tt.

Tuy nhin mt CSDL Multimedia n gin t ra qu n gin v km hiu qu nu xt

thm mt s kha cnh. V d, mt media tm tt c th lit k nh th l mt c

trng, tuy nhin khi chng ta tm kim vi c trng l thnh ng th c th s

khng tm thy nh th v h thng khng th hiu c rng nh th v thnh

ng l tng t nhau. Cc hn ch v mt tng ngha ny cng thng rt hayxy ra i vi CSDL vn bn. Mt vn na m chng ta cng cn phi quan tm l

ngi dng thng hay tm kim cc i tng c cha mt hoc nhiu cc c trng

khc nhau v mt thc t l mc d sau mt s ln chnh sa li cu hi ca mnh mt


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cch hon chnh th cc kt qu tr v tng ng vi cu hi vn cha chnh xc vi

nhng g ngi dng thc s mong mun, iu ny c th hin r nht trong trng

h p chng ta tm kin trn web s dng cc cng c tm kim nh Google hocAltaVista.

Ngc li, y cng tn ti cc trng hp khi ngi dng mun mrng kh nng

tm kim (tm kim mt cch chnh xc hn bng cch khai bo cu hi r rng hn)

th c th s khng thu c kt qu no, trong khi nu n gin ho bt cu hi th

li tm c cc thng tin mnh mong mun.

Cui cng, khi ngi dng a ra cu hi c dng hy tm tt c cc hnh nh m

Jane Shady v Denis Dopeman c mt ti a im A, nu kt qu tm kim tr v ltrng th ngi dng c th suy nghl a im A c th tng t nha im B

v sa li cu hi bng cch thay th vic tm kim ti a im A bng vic tm kim

ti a im B, iu ny dn n vic chnh sa li cu hi bng cch thay th mt

hng s c th ny bng mt hng s khc. Cc v d trn a n vic thc y vic

tm ra mt cu trc khc xc nh CSDL Multimedia h trc cc vn d v ng

ngha cng nh k tha c mi quan h gia cc c trng.

2.4.4 nh ngha v mt CSDL Multimedia c cu trc

Mt CSDL Multimedia c cu trc l mt tp gm c 5 thuc tinh

({M1,..,Mn),,,inh,subst) trong :

l mt media tm tt.

l mt quan h tng ong trn .

l mt th t b phn trn tp ca cc lp tng ng trnF.


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inh: gi s cho bit Nh vy inh l

mt nh x kt hp vi mi c trng f mt tp cc c trng bn dif y

theo th t trn c trng.

Subst l mt nh x t n

hiu r hn, chng ta xem xt v d sau:

Mt CSDL Multimedia c cha 3 loi media tru tng l hnh nh, m thanh v video

c lit k di y

Media Object Part_frame Feature_s)

image Photo1.gif _ Church,durnstein,danube,subrahmanian

image Photo2.gif _ Cathedral,melk,subrahmanian

image Photo3.gif _ Church,st.paul,rome

Video Video1.mpg 1-5 Church,durnstein,stream

Video Video1.mpg 6-10 stream

Audio Audio1.wav 1-20 St.peters,tiber,rome

Bng 2.5

T p cc c trng F c cha: church, durnstein, danube, subrahmanian,

cathedral, melk, st. paul. Rome. Stream. Restaurant, st.peters, tiber.

cho bit :

o Church cathedral.o RiverStream


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Quan hcho bit

Hnh 2.4

C ngha l

[tiber] [river], [danube] [river].

[st.paul] [church], [st.peter] [church].

Cch nh ngha trn tuy cung cp y hn cc thng tin hu ch cho vic tm kim

v trnh by cu trc n gin ca mt h CSDL Multimedia c cu trc nhng n vn

cha cung cp c mt cu trc ch s ho m h thng CSDL Multimedia dng t

chc v lu tr d liu. Trc khi a ra mt cu trc ch s ho thch hp, chng ta s

c ra mt ngn ng truy vn n gin dng truy vn d liu Multimedia. y

chng ta trnh by ngn ng truy vn trc v chng ta ch c c mt cu trc ch s

ho c hiu qu khi m chng ta ti u c cc kiu truy vn m ngi s dng

mong mun .

2.4 Ngn ngtruy vn khai thc dliu multimedia

Trong phn ny, chng ta s trnh by mt ngn ng truy vn n gin c xy dng

da trn SQL dng khai thc d liu Multimedia. Chng ta ch ra c rng mt

media tm tt c thc dng m t cc loi d liu media khc nhau s dng

kin trc m tng nht. Vic mrng ngn ng truy vn SQL s dng cho vic truy

vn d liu c xy dng bi kin trc m tng nht s l tin chng ta tip

tc m rng ngn ng truy vn dng cho vic khai thc cc d liu media c xy

dng theo kin trc lai ghp


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2.4.1 Truy vn SMDSs (m tng nht)

Cc hm cbn ca SMDSs bao gm:

FindType(Obj): hm ny s dng i tng media Obj lm u vo v s tr vkiu ca i tng, v d:

o FindType(image1.gif) =gif.

o FindType(movie1.mpg) = mpg.

FindObjWithFeature(f): hm ny s dng c trng f l gi tru vo v tr v

mt tp tt c cc loi i tng media m c cha c trng f, v d

o .

o

FindObjWithFeatureAttr(f,a,v): hm ny s dng c trng f, mt thuc tnh tn

a kt hp vi c trng ny v mt gi tr v l u vo. Gi tr tr v s l tt c

cc i tng o c cha c trng v gi tr ca thuc tnh a trong i tng o l

v. V d:

o : cu hi ny i hi tm

tt c cc i tng media m c s xut hin ca Jane Shady trong chico mu blue.

o cu hi ny i hi tm tt c

cc i tng media m mt con voi c mang mt ci n mu xut

hin.

FindFeaturesInObj(Obj): cu hi ny i hi phi tm tt c cc c trng c

mt trong mt i tng media cho. Kt qu tr v l mt tp bao gm tt c

cc c trng. V d:

o cu hi ny yu cu tr v tt c cc c

trng c trong file nh im1.gif.


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o cu hi ny yu cu tr v tt c cc

c trng c trong 5 frame u tin ca file video video1.mpg.

FindFeatureandAttrinObj(Obj): hm ny cng c chc nng tng t nh hmtrc ngoi tr vic n tr v mt quan h c schema nh sau: (Feature,

Attribute,Value) trong cp 3 (f,a,v) xut hin trong quan hu ra nu thuc

tnh a ca c trngfc xc nh v c gi tr l v. V d:

o c th tr v kt quc m tbng

sau

Feature Attribute Value

John age 32

John address 32 PicoLane.Mclean.VA 22050.

Mary age 46

Mary address 16 ShawRoad.Dumfries.VA 2290s.

Mary employer XYZCorp.

Mary boss David

Bng 2.6

SMDS-SQL mrng ca chng ta s bao gm tt c cc cu lnh chun ca SQL c

b sung thm mt sc trng ca d liu Multimedia vo SQL (b sung thm vo

Select, From, Where)

Tuyn b Select c th cha thc thmedia. Mt thc th media c nh

ngha nh sau:

o Nu m l mt i tng media lin tc, i vj l 2 s nguyn khi m

: [i,j] l mt thc th media th hin mt tp tt c cc frame ca i

tng media m nm trong (v ch trong) khong i vj.

o Nu m khng phi l mt i tng media lin tc th khi m l mt

thc th media.


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o Nu m l mt thc th media v a l mt thuc tnh ca m th khi d

m.a l mt thc th media.

Tuyn bFrom c th c cc thc th theo mu sau: (media) (source) (M), cngha l ch c cc i tng media kt hp vi tn ca kiu media v tn ca

d liu ngun c xem xt dn khi thc hin cu hi v Ml mt bin c

xp loi trn cc i tng media .

Tuyn bWhere cho php c cc biu thc c dng term In func.call. Trong :

o Term c th l mt bin (trong trng hp ny c sp xp trn kiu tr

v ca func.call) hoc l mt i tng c kiu u ra ging nh

func.call.

o Func.callk mt trong 5 hm nu ra trn.

Chng ta cng xem xt mt vi v d

Tm tt c cc i tng nh hoc video c cha c Jane Shady v Denis

Dopeman.SELECTM

Select M

FROM smds source M

WHERE (FindType(M)= Video OR FindType(M)=Image

AND

M IN FindObjWithFeatureand(Jane Shady) And

M IN FindObjWithFeatureand(Denis Dopeman)

Tm tt c cc nh v video m i tng Jane Shady mc o vt mu tm

SELECT M

FROM smds source M

WHERE FindType(M)=Video OR FindType(M)=Image

ANDM IN FindObjWithFeatureandAttr(Jane

Shady,suit,purple)

Tm tt c cc nh c cha c Jane Shady v Denis Dopeman v Jane ng bn

tri Denis


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SELECT M

FROM smds source M

WHERE FindType(M)=Image AND

M IN FindObjWithFeature(Denis Dopeman) AND

M IN FindObjWithFeature(Jane Shady) AND

Left (jane Shady,Denis Dopeman.M)

y c mt ch l quan hleftc s dng trn l mt quan h media

tm tt ca CSDL hnh nh

Tm tt c cc nh c Jane Shady cng vi i tng xut hin trong on

Video cng vi Denis Hopeman. Khc vi cu hi trc, cu hi ny i hiphi c cc thao tc kt hp gia cc loi d liu khc nhau. thc hin c

cu hi ny, chng ta phi s dng cc bin m rng nh l Person, bin ny

c dng tham chiu n i tng cha xc nh c danh tnh trong

on bng video.

2.4.2 Truy vn d liu multimedia m t di kin trc lai to.

Trong phn trc, chng ta trnh by ngn ng SMDS-SQL nh l mt m hnh

truy vn cc di tng Multimedia lu tr trong kin trc thng nht. Trong kin trc


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ng nht, tt c cc d liu ngun c truy vn u l SMDSs, trong khi trong kin

trc lai to cc cch thc m t khc (non-SMDS) cng c s dng. Cch thc m t

d liu kiu lai to thng c hai phn chnh: Mt tp cc i tng media c m t di dng ng nht.

Mt t p cc kiu media khc nhau m c cu trc truy nh p v truy vn

ring.

mrng ngn ng truy vn SMDS-SQL thnh ngn ng c th truy vn c cc

d liu c m t di dng lai to (HM-SQL) cc yu cu sau bt buc phi c:

HM-SQL phi c kh nng thc hin tt c cc cu hi s dng ngn ng ring

i vi ngun d liu khng ng nht ny.

HM-SQL phi c c ch joins hoc cc thao tc i s nh phn c trch

nhim joins gia 2 ngun d liu SMDS v non-SMDS.

Ngn ng HM-SQL cng tng t nh ngn ng SQL chun ngoi tr cc mnh

Select, From. Where c mrng nh sau:

Mnh SELECT v WHERE c mrng ging nh vi ngn ng SMDS-

SQL.

Tuyn b Where cho php s c mt ca biu thc c dng Term IN MS :

func_calltrong :

o Term:c th l mt bin hoc l mt i tng c kiu u ra ging htvi ca func_call c nh ngha trong media gc v .

o Nu MS=SMDS hoc hfunc_callthuc 1 trong 5 hm inh ngha

trn hoc

o MS khng phi l mt ngun SDMS v func_calll mt cu hi trong

QL(MS).

Khi c 2 s khc nhau gia SMDS-SQL v HM-SQL l:

o func_callxut hin trong mnh where cn c ch thch mt cch

tng minh vi media gc km theo v


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o Cc cu hi c xy dng t cc ngn ng hi p ca tng loi d liu

non-SMDS c thc nhng vo bn trong cu lnh truy vn ca HM-

SQL. iu ny lm cho HM_SQL trnn ht sc mnh m v linh hot.Cn c vo iu ny chng ta c th thc thi cc cu hi i vi cc

ngun d liu khc nhau.

Xt mt s v d sau:

Gi s chng ta c 2 ngun d liu video video1 v video2, ngun video1 c

trin khai qua hnh thc SDMS, ngun video2 c trin khai qua hnh thc

non-SDMS (gi l videob). Cu hi ca chng ta y l hy tm tt c cc

video clip c mt Denis Hopeman t c 2 ngun d liu video1 v video2. Cu

hi ny c thc din t bng ngn ng HM-SQL nh sau:

Trong cu hi ny, chng ta tm kim tt c cc Ms m chng tr v kt qu

mong mun t c 2 ngun d liu (SDMS v non-SDMS).

Cng vi cu hi trn nhng y chng ta thm vo mt ngun d liu mi l

d liu hnh nh (idb) c trin khai di hnh thc non-SDMS v gi s d

liu hnh nh ny c ring chc nng tm kim getpic(obj) vi tham su vo

l obj v kt qu tr v l mt cp bao gm mt nh (file nh) v th t c lin

quan. Gi s chng ta mun tm kim trn c 3 loi d liu ny (video1, video2,

idb) c mt ca i tng Denis Hopeman th cu hi din t bng ngn ng

HM-SQL c th nh sau:

Select M

From sdms Video1, vieob Video2


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Where M IN sdms: FindObjWithFeature(Denis

Hopeman) OR

M IN videodb: FindVideoWithObj(Denis Dopeman)

UNION

(Select M.file

From imagedb idb M

Where M In imagedb:getpic(Denis Dopeman)

Gi s chng ta mun tm tt c cc i tng c mt cng vi Denis Dopeman

trong tt c cc ngun d liu (video1, video2, idb), cu hi s nh sau

2.4.3 Ch s ho SMDS vi ch so.

Trong cc phn trc, chng ta trnh by cc cch thc truy vn CSDL

multimedia di c 2 hnh thc m t l ng nht v lai to. Cc ngun d liu non-

SMDS c ch s ho bi cc cch ring ca chng, y chng ta i su vo tmhiu cch thc ch s ho i vi cc ngun d liu SDMS.

Gi s chng ta c trc mt SMDS c dng:


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trong

Chng ta phi ch ra c mt cch thc ch s ho c hiu qu d liu ny, tng c

bn y l:

Featuretable: y l mt bng bm c cha tt c cc c trng c trong .

Mi bng bm v trIc cha mt i din featurenodes c bm n v tr i.

Statetable: l mt bng bm cha tt c cc trng thi thuc . Cng ging

nhfeaturetable, statetable cng cha mt i din ca statenotesc bm

n v tr xc nh.

Featurenodes: mifeaturenodes bao gm cc thnh phn sau:

o Tn ca c trng (v d Denis Dopeman).

o Mt danh sch cc nt con (nu f1 v f2 l cc c trng trong

chng ta ni rngf2 l con caf1 nuf2f1 v khng c mt c trngf3

khc ( ) mf2


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o Mt danh sch cc mi quan h m thnh vin ca n tr n

featurenodes, bng trc gic chng ta c th thy c l c mt con tr

trnfeaturenodesfnu c trng c trong cu hi trng thi .Cu trc d liu ca SMDS c m t nh sau:

Type featurenode = record of

name: String ;/* Tn ca c trng */

children: ^ node1; /* trn danh sch cc on tr trn nodes con */

statelist: ^ node2 ;/* trn danh sch cc on tr trn cc trng thi c cha c trng ny */

replacelt: ^ node3; /* trn mt danh sch bao gm cc con chu kt hp vi cc

trng thi c th cho l c c trng kt hp vi node */

end record;

type node1 = record of

element: ^ featurenode; /* trn node con ca mt featurenode */

next: ^ node1; /* trn nod con tip theo */

end record;


state: ^ statenode; /* trn danh sch kt hp vi trng thi */

link: ^ node2; /* node tip theo */

end record;


feat: ^ featurenode; /* trn mt node m c th cho l c c trng kt hp vi node hin thi

*/

link1: ^ node3;

end record;


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type statenode = record of

rep: framerep;

flist:^

node4;end record;


f: ^ featurenode;

link2: ^ node4;

end record;

Hnh 2.5: V d vstatetable


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Chng ta hy xem xt mt v d ca SDMS bao gm 3 media tru tng bo gm : d

liu nh, video v m thanh (audio) c ni dung nh sau

Media tru tng Trng thi Cc c trngImg Im1

Im2

Im3

john, mary

john, mary, lizt

lizt, mary

Video Vid1: [1,10]

Vid1: [11,20]

Vid1: [21,40]

Vid2: [1,20]

Vid2: [21,30]

john, singing

john, mary, dancing

john, mary, lizt, singing, dancing

ed, speaking

man, speaking

Audio Disk1: [1,20]Disk1: [21,40]

John, singingwoman, speaking

Bng 2.7

Hnh 2.5 cho chng ta thy mt v d vstatetable (n gin chng ta khng

cp n cc hm bm c s dng) v d v mt featuretable. Mt trong 10

trng thi lit k trn c lu tr trong statetable cng vi 9 c trng.Trong trng hp ny phi ch l singing v dancing c xem nh l

cc c trng.

Th t trn cc c trng c th hin hnh di

Hnh 2.6

Chng ta ch ra c s kt hp ca featurelist vi cc trng thi im1 v

disk1: [1,20], cc featurelist khc khng c th hin ra y nhm mc ch

n gin ho.


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Tng t nh vy chng ta ch ra statelist kt hp vi cc c trng man v lizt.

Mi lin h kt h p gia cc media tru tng ny c th lu tr trong mt

CSDL quan h chun.


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CHNG 3

H QUN TR C S D LIU A PHONG TIN YUCU V CC VN

Trung tm ca mt h thng thng tin multimedia chnh l h qun tr CSDL

MULTIMEDIA (MDBMS). Theo truyn thng, mt CSDL bao gm mt b cc d c

lin quan v mt thc th cho trc hoc mt h qun tr CSDL (DBMS) l mt b cc

d liu c lin quan n nhau vi mt tp hp cc chng trnh c dng khai bo,

to lp, lu tr, truy cp v truy vn CSDL. Tng t nh vy, chng ta c th xem

mt CSDL MULTIMEDIA l mt tp cc loi d liu multimedia nh vn bn, hnh

nh, video, m thanh, cc i tng ho.Mt h qun tr CSDL MULTIMEDIA

(MDBMS) cung cp h trcho cc loi d liu MULTIMEDIA trong vic to lp, lu

tr, truy cp, truy vn v kim sot.

S khc nhau ca cc kiu d liu trong CSDL MULTIMEDIA c thi hi cc

phng thc c bit ti u ho vic lu tr, truy c p, ch s ho v khai thc.

MDBMS cn phi cung cp cc yu cu c bit ny bng cch cung cp cc cch

tm tt bc cao qun l cc kiu d liu khc nhau cng nh cc giao din thch hp

th hin chng.

3.1 Mcch ca MDBMS

Mt MDBMS cung cp mt mi trng thch hp s dng v qun l cc thng tin

CSDL MULTIMEDIA. V vy, n phi h trcc kiu d liu MULTIMEDIA khc

nhau bn cnh vic phi cung cp y cc chc nng ca mt DBMS truyn thng

nh khai bo v to lp CSDL, khai thc d liu, truy cp v t chc d liu, c lp

d liu, tnh ring, ton vn d liu, kim sot phin bn. Cc chc nng ca MDBMS

c bn tng t nh cc chc nng ca DBMS, tuy nhin, bn cht ca thng tin


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MULTIMEDIA to ra cc i hi mi. Bng cch s dng cc chc nng tng qut

ca DBMS chng ta c th trnh by mc ch ca MDBMS nh sau[1]:

S thng nht: bo m rng mt d liu khng phi to li khi cc chng

trnh khc nhau i hi d liu .

c lp dliu: m bo s tch ri gia CSDL v cc chc nng qun tr t

cc chng trnh ng dng.

iu khin nht qun: m bo s ton vn ca CSDL MULTIMEDIA thng

qua cc quy tc dc p dng trn cc giao dch ng thi.

Stn ti: bo m cc i tng d liu tn ti qua cc giao dch khc nhau

cng nh cc yu cu ca chng trnh.

Tnh ring: ngn chn cc truy cp v sa cha cc d liu c lu tr mt

cch tri php.

Kim sot ston vn; bo m s ton vn ca CSDL mt giao dch ny sang

mt giao dch khc thng qua vic p t cc rng buc.

Kh nng phc hi: phi c cc phng thc cn thit m bo rng kt qu

ca cc giao dch tht bi khng lm nh hng n d liu lu tr.

H tr truy vn: bo m cc c ch truy vn ph hp vi d liu

MULTIMEDIA.

Kim sot phin bn: t chc v qun l cc phin bn khc nhau ca cc i

tng lu tr c thc yu cu bi cc ng dng.


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Hnh3.1: Kin trc bc cao cho mt MDBMSp ng cc yu cu cho dliu

MULTIMEDIA

i vi vic iu khin nht qun, mt giao dch l mt chui cc hng dn c

thc thi mt cch hon ton hoc khng hon ton, i vi trng h p khng hon

ton CSDL sc khi phc li trng thi trc , vic a ra c mt c chtng ng m bo cho vic nht qun l mt vn kh khn i vi CSDL

MULTIMEDIA. Cc CSDL quan h truyn thng s dng mt bn ghi hoc mt bng

duy nht nh l mt n v nht qun. CSDL MULTIMEDIA thng s dng mt i

tng n l (hoc i tng ghp) nh l mt n v logic ca truy cp. Nh vy mt

i tng MULTIMEDIA n l c th to thnh n v nht qun[14].

i vi vn lu tr, mt phng thc n gin l lu tr cc tp MULTIMEDIA

trong cc tp tng ng ca hiu hnh. Tuy nhin vi c th l dung lng ln, ccd liu MULTIMEDIA l cho chi ph trin khai theo cch thc ny trnn tn km.

Hn na, h thng cng cn phi lu tr cc metadata MULTIMEDIA v c th c cc

i tng MULTIMEDIA tng hp. V vy, hu ht cc MDBMS phn loi thnh 2

phn l cnh v tm thi v ch lu tr cc d liu cnh sau khi cc giao dch


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c c p nht. Cc d liu tm thi chc dng trong cc chng trnh hoc cc

giao dch khi chng c thc thi v c loi b sau .

Thng thng, mt cu hi s la chn mt tp con ca cc i tng d liu da trncc m t ca ngi dng (thng l thng qua cc ngn ng truy vn) v truy nhp d

liu no. Mt cu hi thng c nhiu thuc tnh khc nhau, c th l da trn t kho

hoc hng theo ni dung v thng l tc ng ln nhau. V vy, cc chc nng cho

phn hi c lin quan, cng thc ca cu hi, cc kt qu tng t, v cch th hin

kt qu r rng l rt quan trng trong MDBMS.

Khi cc ng dng cn truy cp n cc trng thi khc nhau ca mt i tng th vn

kim sot phin bn i vi i tng MULTIMEDIA khi chng c truy cphoc sa cha trnn rt quan trng. Mt DBMS cung cp cc kh nng truy cp nh

vy thng qua cc phin bn ca cc i tng lu tr, i MDBMS khi m phi lu

tr mt khi lng d liu khng l th vn kim sot phin bn cng trnn quan

trng. Mt khc, vic qun l phin bn khng ch p dng cho mt i tng ring l

m n cn c p dng qun l cc i tng phc tp to nn CSDL

MULTIMEDIA[1].

Cc tnh cht c bit ca d liu MULTIMEDIA cng i hi phi c cc tnh nng

c bit mi h trcho n nh kt hp v phn r cc i tng, qun tr dung

lng khng l d liu MULTIMEDIA, lu tr v khai thc hiu qu, c kh nng lm

vic c vi cc i tng d liu tm thi hoc mt phn ca chng.

3.2 Cc yu cu ca mt MDBMS

c c mt MDBMS p ng c cc yu cu nu ra trn, chng ta cn

phi c c mt s cc yu cu c th cho n, cc yu cu y bao gm:

y cc kh nng ca mt DBMS truyn thng.

C kh nng lu tr ln.

C kh nng khai thc d liu thun tin.


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C kh nng tch hp, tng hp v th hin.

H trtruy vn multimedia.

C giao din multimedia v tng tc.Bn cnh cc yu cu va nu, cho h thng hot ng c th hot ng tt chng ta

cng cn phi gi quyt cc vn sau:

H thng CSDL MULTIMEDIA sc xy dng nh th no c th bao

gm cc lnh vc ng dng khc nhau.

Xy dng phn ht nhn cho vic phn r , lu tr v qun l thng tin mc

no? Cc cng ngh, cu trc nn tng c sp xp v s dng nh th no?

Cc kin thc v tng hp d liu i vi CSDL MULTIMEDIA, lm th no

c th pht trin c mt ngn ng truy vn ng tin cy v c hiu qu

h trcho v s phng thc truy nhp v cc kiu i tng khc nhau. Lm

th no ngn ng truy vn h trc cc c tnh v hnh thi khc nhau

ca d liu MULTIMEDIA.

Xc nh c h tng th hin no m mt h thng MULTIMEDIA phi c

t c cc yu cu v cch thc th hin khc nhau. Lm cch no h tr

vic ng b ho vic th hin cc d liu tm thi cng nh cc d liu b

phn ca cc d liu MULTIMEDIA khc nhau.

Gi s cc kiu media khc nhau c cc yu cu cp nht v sa i thng tin

khc nhau th h thng s cp nht cc thnh phn ny nh th no.

Nh hnh 3.1 chng ta thy kin trc bc cao dnh cho mt MDBMS ch ra c

mt s cc yu cu cn phi t c. Kin trc ny bao gm hu ht cc khi chc

nng v qun l i km vi DBMS truyn thng.. Ngoi ra, n cng bao gm mt smodul c bit phc v cho vic qun tr d liu MULTIMEDIA nh tch hp cc

phng tin v qun l cc i tng. Tuy nhin hu ht cc chc nng thm vo

DBMS truyn thng u nm ngoi phn li ca MDBMS bao gm th hin, giao din,

v qun l cu hnh[1].


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3.2.1 Kh nng qun tr lu tr ln

Hnh 3.2

Cc yu cu v kh nng lu tr ca cc h thng MULTIMEDIA c thc c

trng bi kh nng lu tr ln v cch thc t chc theo th bc (dng kim t thp)

ca h thng lu tr. Vic lu tr theo th bc t cc i tng d liu

MULTIMEDIA trong mt h thng phn bc bao gm cc thit b khc nhau, c th l

trc tuyn (online), khng trc tuyn (offline). Mt cch tng qut, mc cao nht ca

h thng s cho ta hiu sut cao nht, kh nng lu tr nh nht, chi ph cao nht v s

cnh t nht. Cc lp cao trong h thng phn cp ny c th s dng lu tr cc

i tng tm tt nh hn ca mt d liu MULTIMEDIA hon chnh vi mc ch

cung cp kh nng duyt v xem trc nhanh i vi ni dung ca d liu. Chi ph v

hiu sut (tnh v mt thi gan) s gim dn nu ta i xung cc lp pha di ca h

thng phn c p, cng vi iu ny l s tng ca kh nng lu tr v tnh cnh.

Thng thng trong hu ht cc h thng lu tr MULTIMEDIA, mc cao nht ca


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lu tr thng l RAM, tip theo l a t, cc thit b ny cung cp cc dch v

trc tuyn (online services). Cc thit b lu tr quang hc cung cp mc lu tr tip

theo, khi nim trc tuyn y c th hiu l gn nh, tiu biu cho cc thit b lutr kiu ny l cc jukebox (CD-DVD jukebox). Mc thp nht trong h thng lu tr

phn cp c th l cc thit b nh bng t, a quang hoc cc thit b tng t, cc

thit b ny cung cp kh nng lu tr offline v c th khng cn kt ni trc tip vi

my tnh. Chng cung c p kh nng lu tr v tnh cnh cao hn nhng cng c

hiu sut km nht v thi gian truy nh p. V nhng l do trn, mt MDBMS phi

qun l v t chc vic lu tr i vi bt k mc no ca h thng phn cp, n phi

c cch tng chuyn cc i tng d liu MULTIMEDIA t mt mc nyca h thng lu tr phn cp sang mc khc, vic chuyn cp ny phi da trn tn

sut s dng ca d liu MULTIMEDIA. Trong trng hp d liu MULTIMEDIA

c lu trcc thit b offline th MDBMS cng phi c c cc thng tin trgip

cho vic d dng xc nh cc thit b c th c cha cc thng tin cn truy xut.

3.2.2 H tr truy vn v khai thcd liu.

Truy vn i vi d liu MULTIMEDIA bao gm cc kiu d liu khc nhau, cc tkho, thuc tnh, ni dung vvDo ngi dng c th c cc cch suy nghkhc nhau

v d liu MULTIMEDIA v vy kt qu thu c t vic truy vn d liu

MULTIMEDIA c th khng hon ton chnh xc v c th ch l cc kt qu tng t

hoc l mt phn ca kt qu hn l cc kt qu chun xc. Do vic c th kt qu l

khng chnh xc nn chng ta phi c kh nng phn hng cc kt qu thu c sao

cho chng gn vi yu cu truy vn nht, tng t nh vy chng ta cng phi c cc

phng thc loi b bt nhng kt qu khng tho mn yu cu truy vn. Vic lm

ny s gim thiu cc sai st v mt tnh ton trong qu trnh tm kim.


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3.2.3 Tch hp cc phng tin, tng hp v th hin

Gi s tnh a dng ca cc kiu d liu c h tr, mt MDBMS cng phi cung

c p kh nng tch h p cc loi d liu ny to nn cc kiu d liuMULTIMEDIA mi v th hin cc d liu ny khi c yu cu trong mt khung thi

gian yu cu. phc tp ca vic tch hp, tng hp v th hin b tng thm bi cc

c tnh cbn ca d liu MULTIMEDIA nh tnh lin tc (tm thi) ca d liu

MULTIMEDIA c bit l vi cc kiu d liu nh video, hot hnh hoc m thanh.

Hn na, mt vi ng dng c th nh cc h thng thng tin a l c thi hi

MDBMS cung cp cc thng tin b phn (v mt vng, min no ). Tt c cc yu t

ny kt hp vi nhau lm cho vic tng hp v th hin MULTIMEDIA trthnh mt

quy trnh phc tp m MDBMS phi cung cp p ng cc yu cu m ngi dng

i hi.

Cc vn v tch hp c thc ci thin trong mt s trng hp, c bit l khi

cc h thng CSDL MULTIMEDIA c xy dng nhm phc v cho cc cng ng

ngi dng xc nh trc. Trong cc trng hp c bit ny, MDBMS c th h tr

mt s tnh nng m cc ng dng khc khng cn n.

3.2.4 Giao din v tng tc.

S khc nhau v bn cht ca cc d liu MULTIMEDIA i hi phi c cc giao din

khc nhau tng tc vi d liu. Thng thng, mi loi d liu c cc phng thc

truy nhp v th hin ring ca mnh, v d nh d liu video v m thanh si hi

cc giao din ngi dng khc nhau th hin v truy vn. i vi mt vi ng dng

Multimedia, c bit l s c mt ca cc loi d liu c tnh lin tc ngi dng

thng i hi phi c cc kh nng tng tc vi d liu ( chng hn nhi vi d

liu VCR th ngi dng thng mong mun c chc nng nh tua ln (fast forward)

hoc tua ngc li (reverse)). Khi m mt h thng Multimedia cung cp cc dch v


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nh vy th n phi c lin kt vo CSDL c bit l vic khai thc cc i tng,

tng hp v ng b chng.

3.2.5 Hiu sut.

Hiu sut l mt vn quan trng cn c xem xt i vi mt MDBMS. Cc h

thng CSDL MULTIMEDIA to ra hiu sut da trn s ti u ho vic truy nhp ti

cc media, lu tr, ch s ho, khai thc v truy vn . S c tham gia ca nhiu kiu d

liu khc nhau trong CSDL MULTIMEDIA c thi hi mt s phng thc c bit

ti u ho vic truy cp, lu tr, ch s ho v khai thc. Cc yu cu ny bao gm

hiu qu, tnh n nh, m bo v ng b vic trao i d liu, cht lng ca dchv (QoS).

3.3 Cc vn ca MDBMS

p ng c cc yu cu nu ra phn trn, MDBMS cn phi xc nh c

mt s vn quan trng bao gm:

M hnh ho d liu MULTIMEDIA.

Lu tri tng multimedia. Tch hp, trnh din, cht lng dch v multimedia.

Ch s ho, khai thc v duyt.

H trtruy vn multimedia.

Qun tr d liu MULTIMEDIA phn tn.

H trca h thng.

3.3.1 M hnh ho d liu MULTIMEDIAM hnh d liu l n v trung tm ca mt h thng CSDL MULTIMEDIA. Mt m

hnh d liu cn phi tch ri ngi dng ra khi chi tit ca vic qun l cc thit b

lu tr v cu trc lu tr. iu ny i hi phi pht trin cc m hnh d liu tng


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ng t chc cc kiu d liu khc nhau tng g p trong cc h thng CSDL

MULTIMEDIA.

Cc m hnh d liu MULTIMEDIA (cng ging nh cc m hnh d liu truynthng khc) nm bt cc c tnh cnh cng nhng ca ni dung CSDL v v vy

n cung cp cc khun mu cbn cho vic pht trin cc cng c cn thit s dng

d liu MULTIMEDIA. Cc thuc tnh cnh c th bao gm cc i tng to nn

d liu MULTIMEDIA, mi lin h gia cc i tng, thuc tnh ca cc i tng

Cc c tnh ng bao gm s tng tc gia cc i tng, s hot ng trn i

tng, cc tng tc ca ngi dng.

Tuy nhin, do cc tnh cht c bit ca mnh, d liu MULTIMEDIA i hi phi ccc quan tm mi khi chn la m hnh d liu. V d, mt vi kiu d liu

MULTIMEDIA (chng hn video) hoc mt nhm cc kiu (video v hnh nh) c th

i hi cc m hnh d liu c bit ci thin hiu qu v tnh mm do. Hn na,

do tm quan trng ca vic tng tc trong cc h thng MULTIMEDIA nn vic n

c h trbi cc m hnh d liu trnn quan trng.

Rt nhiu cc m hnh d liu khc nhau nh l mng li, lin h, ng ngha, v

hng i tng ang tn ti v mt vi s trong chng c xem xt thit lp

CSDL MULTIMEDIA. C hai cch tip cn cbn trong vic m hnh ho d liu

MULTIMEDIA l:

Phng php th nht: xy dng mt m hnh d liu MULTIMEDIA trn nn

tng ca m hnh d liu ca mt CSDL truyn thng (thng l CSDL quan

h hoc CSDL hng i tng) bng cch s dng cc giao din tng ng

i vi d liu MULTIMEDIA. Cc vn ny sinh vi cch tip cn ny l

cc cu trc bn di (ca CSDL truyn thng) khng c thit k dnh cho

d liu MULTIMEDIA, hn na s khc bit c bn cc yu cu ca mt

CSDL truyn thng i vi CSDL MULTIMEDIA khin cho giao din tr


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thnh ni nghn c chai trong ton b h thng. Cc vn ny dn ti cch

tip cn th hai.

Phng php th hai: pht trin cc m hnh d liu thc th dnh cho d liuMULTIMEDIA tu ch khng xy dng trn c s ca cc CSDL truyn

thng, tuy nhin mi ngi u nht tr rng cc n lc nh vy u phi da

trn k thut hng i tng.

3.3.2 Lu tri tng MULTIMEDIA

Lu tr vt l cc d liu multimedia i hi cc phng thc chuyn i, qun l,

trao i v phn phi mt s lng d liu khng l, cc h thng multimedia thngthng s dng phng thc phn cp i vi cc thit b lu tr. Cc thit b lu tr

online c tc cao nh RAM, HDD lu tr cc d liu ang c x l trong khi

cc thit b lu tr offline (c tc chm) dng lu tr cc d liu c tnh cht di

hn, cnh. Khi , hiu sut s ph thuc vo kh nng ca cch chuyn i cc

d liu multimedia tng ng vi mc ti u ho trong h thng lu tr phn cp.

Cc cch nn d liu kt hp vi cc cch chuyn i d liu gip phn lm gim

cc yu cu khng l v mt lu tr, phng thc c bn c s dng y lchuyn i d liu multimedia sang mt s vng chuyn i loi b s d tha ca

d liu gc, cc qu trnh gii nn s lm nhim v chuyn i ngc cc d liu ny

v dng gc ca n. Qu trnh ny s dn n vic mt mt d liu, tuy nhin vic mt

mt ny c hu ht cc ng dng multimedia cho php.

Ph thuc vo mc ca ht nhn m mt i tng multimedia c th th hin ton

b hoc mt phn on video, mt frame, mt hnh nh ring l thm ch c tng i

tng c th trong mt nh hoc mt on video. Vn chnh t ra y l kh

nng lu tr c hn, bng thng hn ch ca h thng lu tr cc knh truyn thng, t

l sn sng ca cc loi d liu multimedia. T l sn sng ca d liu ch ra s lng

d liu ti thiu cn thit i vi mi n v thi gian cn p ng i vi cc i hi


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v yu cu cht lng trong qu trnh th hin cc i tng multimedia. ng t quan

im ny, cc yu cu v lu tr ca d liu multimedia c gii quyt bng cch

phn chia d liu thnh cc i tng multimedia nh hn c th lu tr trong ccn v lu tr nh hn.

Vi vic sp xp lu tr phn cp, cc i tng multimedia c thc lu trcc

mc khc nhau, khi m t l s dng cc i tng d liu multimedia thay i cc

i tng ny cn phi c phn phi li c th l c lu tr trn cc thit b khc,

ti cc mc khc nhau ca h thng lu tr. Vn cn gii quyt lc ny ch l tm ra

gii php ti u cho vic phn r, phn phi v ti phn phi cc i tng multimedia.

3.3.3 Tch hp multimedia, th hin v cht lng ca dch v (QoS)

Khc vi cc d liu truyn thng, d liu multimedia i hi cc rng buc v s th

hin iu ny bt ngun tc tnh lin tc ca mt s kiu d liu multimedia m

chng i hi th hin mt s lng nht nh d liu trong mt khong thi gian nht

nh m kt quem lai cho ngi dng vn phi m bo c c trng ca cc kiu

d liu . Khi m d liu multimedia c b tr phn tn v truyn i trn mng th

cc vn v th hin cng trnn cp thit hn, chng ta bt gp iu ny trongtrng hp bng thng hn ch. Cc d liu lin tc c nh ngha l phc thuc vo

thi gian, v vy thi gian trthnh mt yu t quan trng trong vic phn pht v th

hin chng. V vy trong MDBMS, thi gian hi p i vi mt cu hi thng c

nh gi bi c tnh chnh xc v cht lng i vi cc kt qu khai thc.

ng t quan im ca ngi dng, cht lng, mc chp nhn c v hiu sut

ca cc loi dch v khc nhau c cung cp bi h thng multimedia v c thnh

hng n kt qu ca vic th hin multimedia. V vy, h trcho vic th hin

multimedia trong iu kin ngi dng c th xc nh cc mc QoS khc nhau i

vi cc dch v khc nhau, MDBMS cn phi h trcc mc QoS v mt dch v qun


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l QoS, chng thng thng c thc hin bng cch cung cp mt nh x tng ng

t QoS ca ngi dng sang QoS ca h thng v ngc li.

Khi th hin cc loi d liu multimedia khc nhau chng hn video v m thanh cngvi nhau cc vn v tch hp v ng b cc loi phng tin trnn ht sc quan

trng. MDBMS cn phi cung cp mt cchm bo sng b trong vic th

hin cng nhp ng c cc yu cu khc nh t l sn sng ca d liu v QoS.

Trong mt vi trng hp, MDBMS c th phi da vo mt cch qun l ng b

ho m bo c sng b vi mt kiu d liu cho trc hoc gia cc kiu d

liu khc nhau.

3.3.4 Ch s ho multimedia

Cng nh trong cc CSDL truyn thng, cc d liu multimedia c thc khai thc

thng qua cc nh danh, cc thuc tnh, cc t kho v s lin kt gia chng. Cc t

kho l phng thc chim u th trong vic s dng ch s ho d liu

multimedia. Con ngi thng chn cc t kho t mt tp cc t vng nht nh, iu

ny to ra mt s kh khn khi p dng i vi d liu multimedia v chng thng

c lm mt cch th cng v rt tn thi gian v cc kt qu thng l ch quan vrt hn ch ph thuc vo t vng.

Mt phng thc khc c s dng da trn vic truy cp ni dung, n xem xt n

ni dung thc s ca d liu multimedia hoc xut pht t ng cnh ca thng tin.

Trong thi gian gn y, vic nghin cu ch s ho da trn ni dung c tin

hnh ht sc mnh m vi mc ch l ch s ho d liu multimedia da trn cc c

trng xc nh thu c trc tip t d liu. Cc c trng khc nhau nh mu sc,

hnh dng, kt cu b mt, cc chui c trng v cc c trng khc c dng

ch s ho cc nh.

thu c cc c trng ny i hi phi phn tch tng d liu multimedia, cc

phng thc chnh c s dng i vi d liu nh v d liu video l x l nh,


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on nhn nh v phn tch chui video. i vi d liu video, chui video trc tin

c phn tch thnh cc chui hp thnh, sau cc c trng tm tt (thng l cc

frame kho) sc la chn c trng cho mi chui. Vic ch s ho tip theo ivi d liu video cng da trn cc frame kho cng ging nhi vi d liu nh

i vi d liu m thanh, vic ch s ho da trn ni dung c th c s tham gia ca

vic phn tch tn hiu, tng nhn bit li ni cng vi vic ch s ho da trn t

kho. Mt khc, vic ch s ho c th da trn cc thng tin khc ph thuc vo kiu

ca d liu m thanh, v d mt vi nh pht trin s dng cc c trng v nhp

iu, hp m v giai iu cho vic ch s ho da trn ni dung i vi d liu m

thanh. Tng t nh vy, vic tm kim v khai thc d liu m thanh da trn nidung c xut da trn cc c tnh ca d liu m thanh nh c ch ra

qua cc c trng v m hc v gic quan..

Vic ch s ho da trn ni dung cng gi ra mt vi vn cn quan tm. Trc ht,

cng vi mt d liu multimedia nhng mi ngi c th hiu theo mt cch khc

nhau. Th hai, ngi dng thng cn cc thng tin thay i khc nhau, v vy mt c

trng duy nht c th l khng ch s ho hon ton mt kiu d liu multimedia

cho trc. Mt vn khc cn phi xem xt l vn hiu qu, vic ch s ho phi

nhanh v cc ch s ny phi c lu tr mt cch hiu qu phc v cho vic truy

cp d dng khi m s lng cc d liu multimedia c lu tr l rt ln. Bi v c

tnh vn c ca d liu multimedia l rt khc nhau nn vic ch s ho khng th tin

hnh mt cch hon ton tng, n c nh my tnh c th phn tch d dng mt

bc nh c cha cc tc phm ngh thut, nhng n gn nh khng th tng xc

nh c ngha ca tc phm , iu ch c con ngi lm c.

3.3.5 H tr truy vn multimedia, khai thc v duyt qua.

Cc cu hi ca ngi dng thng c x l s dng cc ch s c sn, tuy nhin

khc vi CSDL truyn thng tnh chnh xc trong tm kim i vi d liu multimedia


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khng phi l chnh xc tuyt i. Thng thng khi so snh hai d liu multimedia th

kt qu thu c thng l gn ng hoc tng t, gi s trong trng hp cc d

liu ny c cng d liu u vo th kt qu thu c t mt cu hi c th sinh ra rtnhiu gi tr. c rt nhiu cc nghin cu i su vo vic tm ra mt phng thc

thch hp trgip cho ngi dng c c mt kh nng hiu qu khai thc cc d

liu multimedia, chng hn thng qua vic cung cp cc giao din thch hp ngi

dng c th duyt mt cch thun li cc kt qu c c t qu trnh tm kim. Vic

h trduyt mt cch trc tip cho php ngi s dng c th khai thc bt k thng

tin no c kh nng lin quan n kt qu hin thi bng cch la chn cc mc d liu

tng ng cn quan tm su hn.Truy vn bng v d (Query-by-Example) l mt phng thc chnh c s dng

nh p cc cu hi i vi CSDL multimedia, c bit l i vi d liu nh. y

ngi dng a ra cc yu cu bng cch s dng mt mu c sn (v d nh mt nh

tng t), v vy giao din c s dng nhp cu hi vo h thng trthnh mt

vn cn phi quan tm. Do tnh cht a dng ca cc kiu d liu multimedia nn

mi kiu d liu multimedia c th phi c cc giao din truy vn khc nhau, vn

cn c xem xt y l lm th no tch hp c cc giao din khc nhau vo

mt h thng tch hp CSDL multimedia. Mt vn khc cng cn phi gii quyt l

vic bao gm truy vn cc d liu khng gian hoc truy vn cc d liu tm thi i

hi phi c cc thng tin khng gian hoc tm thi.

3.3.6 Qun tr CSDL multimedia phn tn

MDBMS phn tn c thc hiu l mt b cc MDBMS c lp (cc MDBMS ny

c th rt khc nhau) nm ti cc v tr khc nhau m c th giao tip hoc trao i d

liu multimedia vi nhau thng qua mng. Cc h thng multimedia thng c phn

tn vi quan nim mt s tng tc multimedia n l thng lin quan n vic d

liu thu c t cc ngun thng tin phn tn khc nhau. iu ny thng thy trong


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cc mi trng multimedia cng tc khi m cc ngi dng c th t cc a im vt

l khc nhau thao tc v l ngi to ra cng mt ti liu multimedia. Ngoi ra, cc vn

v lu tr v pht sinh d liu bt buc cc nh thit k h thng multimedia phib tr d liu multimedia cc a im khc nhau.

h trcho vic truy vn trong mi trng phn tn v cng tc ny , mt MDBMS

phn tn phi xc nh c cc vn tng qut ca CSDL phn tn nh x l truy

vn phn tn v song song, qun tr cc giao dch phn tn , s trong sut d liu, an

ton d liu.. Ngoi ra cc vn v h thng mng nh bng thng hoc tr cng

l cc vn quan trng cn phi lu tm nht l khi chng c xu hng bt li i vi

vic h trQoS.Khng ging nh DBMS truyn thng, vic ti to d liu thng khng c khuyn

khch trong MDBMS phn tn do s lng d liu khng l. M hnh tnh ton

Khch-Ch (client-server), trong cc dch vng dng ca my ch phc v cho

nhiu ng dng khch khc nhau (cc dch v ca server v cc ng dng client c th

nm cc my khc nhau) c chng minh l thch hp nht cho cc cc h thng

multimedia trong c trng hp tng qut cng nhi vi MDBMS phn tn.

3.3.7 S h tr ca h thng

Cc ng dng multimedia v cc h thng CSDl multimedia phn tn t ra cc yu

cu mi i vi tt c cc kha cnh ca h thng my tnh, t cc yu cu v hiu

hnh, h thng mng cng nh cc yu cu v phn cng. Hu ht cc hiu hnh

hin ti cha h trcc x l mang tnh thi gian thc. Mt vi d liu multimedia

chng hn nh cc d liu c tnh lin tc c thi hi cc tnh nng phn pht v th

hin thi gian thc mc d cc yu cu v thi gian thc ny c th khng nghim ngt

nhi vi cc yu cu v thi gian thc thng bt gp i vi phn cng. V vy,

cc h thng CSDL multimedia khng th cung cp y cc tnh nng cn thit theo


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yu cu tr khi cc h tr thi gian thc cho cc thit b multimedia tr thnh mt

phn khng th thiu ca hiu hnh.

Cc c tnh khc ca multimedia chng hn nh s lng ln d liu cn phi lu trc thi hi mt s rng buc c bit i vi h thng v mt qun l b nh, hiu

sut ca CPU. Cc vn khc cng cn phi xem xt n y bao gm vic qun l

cch vo/ra (I/O) ca phn cng nhm mc ch h trcho cc kiu khc nhau c

mt trong CSDL multimedia, h thng mng vin thng cng phi m bo cho vic

truyn ti d liu cho cc mi trng multimedia phn tn p ng cc i hi nghim

ngt ca QoS i vi cc ng dng c th


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CHNG 4

XY DNG H THNG MUA BN HNG QUA MNG

4.2.1. Gii thiu

Thng mi in t ting Anh l Electronic Commerce hay thng vit tt l

eCommerce. Khi ni n thng mi in t l ngi ta hay nghn vic s dng

Internet trgip cho cng vic kinh doanh. Trn thc t, thng mi in t c vai tr

quan trng hn nhiu.

Vy chng ta hiu thng mi in t nh th no?. C mt s kin cho rng:

thng mi in t l mi hnh thc giao dch c h trbi cc phng tin in t.

Ni nh vy c ngha l tt c mi hot ng kinh doanh hin nay u l thng mi

in t v u s dng in thoi, fax hay email... v tt cu l phng tin in t?.

Trc ht, thut ng thng mi in t ch mi c s dng khi c mt s

ngi thc hin c vic mua bn qua mng Internet bng cch tr tin bng mtloi tin c m ho.

Vy thng mi in t ch c th thc hin c qua Internet hay h thng cc

my tnh ni mng?. ng nh vy, nhng khng phi giao dch no trn Internet cng

c gi l

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