C S D Liu Phn Tn ti:Phn mnh dc Nhm 3:Phm V Minh Hong(nhm trng) L Quang Hng Li Ngc Tuyn V Trng Khanh ng Vn Oanh 4/20/20121 Ni Dung: 1. Khi qut v phn mnh d liu 2. Phn mnh dc a. nh ngha,yu cu ca phn mnh dc b. Thng tin cn thit ca phn mnh dc c. Thut ton t nhm d. Thut ton phn mnh 3. Kt lun 4/20/20122 Khi qut v phn mnh d liu nh ngha phn mnh d liu: Phn mnh (fragmentation) d liu l vic chia cc quan h trong mt c s d liu(CSDL) thnh cc quan h nh hn haycn gi l cc mnh (fragment). 4/20/20123 Khi qut v phn mnh d liu V tr ca phn mnh trong thit k cc h c s d liu phn tn 4/20/20124 Khi qut v phn mnh d liu Cc kiu phn mnh d liu: Phn mnh ngang Phn mnh dc Phn mnh kiu kt hp Cc thng tn yu cu cho phn mnh: Thng tinh v c s d liu gm tp cc quan h,tp cc ph thuc Thng tin v cc ng dng gm cc cu truy vn trn cc quan h 4/20/20125 Khi qut v phn mnh d liu L do phn mnh d liu: Xut pht t c im ca CSDL tp trung,cch thc truy cp vo cc CSDL tp trung.c im v yu cu ca ng dng truy vn. Tng mc hot ng ng thi v tng lu lng hot ng ca h thng Mt s hn ch: Tng chi ph truy xut d liu n cc mnh v tng chi ph kt ni cc mnh. Vic kim sot ng ngha,bo m tnh c lp d liu,ton vn d liu s gp kh khn hn. 4/20/20126 Phn mnh dc nh ngha phn mnh dc: Phn mnh dc l s phn chia tp thuc tnh ca mt quan h ton cc thnh tp thuc tnh con, cc mnh dc c c bng cch chiu quan h ton cc trn mi tp thuc tnh con. 4/20/20127Nhm 3 - L Quang Hng Phn mnh dc V d1:cho c s d liu ton cc sau: Phn mnh theo chiu dc quan h BRANCH thnh 2 quan h v v kt qu l: ( ),BRANCHMACNVON[( ), , DDIEMBRANCHMACNTENCN[1 BRANCH 2 BRANCH4/20/20128Nhm 3 - L Quang Hng ( )1, MACN VONBRANCH( )2, , MACN TENCNDDIEMBRANCH( ), , , MACN TENCN VONDDIEMBRANCHPhn mnh dc Yu cu ca phn mnh dc: Gi s ta c quan h R Tp cc thuc tnh ca quan h R: Tp cc mnh ca mnh ca R: K l kha ca quan h R Tnh y :bt k thuc tnh no trong quan h R u c th tm thy trong mi mnh con. Tnh khi phc li: 4/20/20129Nhm 3 - L Quang Hng ; 1 2| ...i i R n R F R R R Re ={ }1 2, ,...,maa aO={ }1 2, ,...,R n F RR R=, , 1. ;|k k knk a k R R F a=e O - e ePhn mnh dc Tnh tch bit: Vi l tp thuc tnh kha ca( )( ), |k j k jk j DR R== CDeO k jvR R4/20/201210Nhm 3 - L Quang Hng Thng tin cn thit ca phn mnh dc Ma trn gi tr s dng thuc tnh: Xt:Q={q1,q2,..,qq} :tp cc cu truy vn R(A1,A2,,An):quan h ton cc :Ma trn thuc tnh s dng.Vi i=1,,q v j= 1,,n Trong : 4/20/201211Nhm 3 - L Quang Hng ( ) ( ),qxnjiA useqA=Thng tin cn thit ca phn mnh dc V d 2:Xt 4 cu truy vn sau i vi quan h BRANCH q1: Tm vn ca chi nhnh theo m chi nhnh SELECTVON FROMBRANCH WHEREMACN=Value q2: Tm tn chi nhnhv vnca tt c cc chi nhnh SELECTTENCN, VON FROMBRANCH q3: Tm tn chi nhnh theo tn a im SELECT TENCN FROMBRANCH WHEREDDIEM=Value

4/20/201212Nhm 3 - L Quang Hng Thng tin cn thit ca phn mnh dc q4:Tm tng vn ca cc chi nhnh ti mi thnh ph SELECT SUM(VON) FROMBRANCH WHERE DDIEM=Value Ma trn gi tr s dng thuc tnh:

4/20/201213Nhm 3 - L Quang Hng A=12341 0 1 00 1 1 00 1 0 10 0 1 1qqqq ( ( ( ( ( 1 2 3 4A A A AThng tin cn thit ca phn mnh dc Ma Trn lc ht : Vi: Trong :ref(qk) :s truy xut n cc thuc tnh (Ai,Aj) cho mi ng dng ca qk ti v tr Sl acc(qk) :s o tn s truy xut ng dng. :[( ( , ) ( , ) ] 1( , ) ( ) ( )k i k j li j l k l kk useq A useq A Saff A A ref q acc q. = = 4/20/201214Nhm 3 - L Quang Hng ( )( )a ,AAnxni jffAA=Thng tin cn thit ca phn mnh dc V d 3: gi s ref(qk)=1 cho tt c qk v Sl. S o tn s truy xut ng dng gi thit nh sau: acc1(q1)=12acc2(q1)=15acc3(q1)=8acc1(q2)=5acc2(q2)=0acc3(q2)=0acc1(q3)=25acc2(q3)=20acc3(q3)=25acc1(q4)=2acc2(q4)=0acc3(q4)=0 Tnh s o i lc gia cc thuc tnh A1 v A3 ng dng duy nht truy xut n c hai thuc tnh ny l q1 nn ta c: 31 3 1 1 1 2 1 3 11 1( , ) ( ) ( ) ( ) ( ) 35lkk laff A A acc q acc q acc q acc q= == = + + =4/20/201215Nhm 3 - Li Ngc Tuyn Thng tin cn thit ca phn mnh dc Ta c c ma trn lc ht thuc tnh nh sau: 4/20/201216Nhm 3 - Li Ngc Tuyn 123435 0 35 00 75 5 7035 5 42 20 70 2 72AAAA ( ( ( ( ( 1 2 3 4A A A AAA=Thut ton t nhm Yu cu thut ton: u vo:mt ma trn gi tr lc ht thuc tnh AA X l:hon v cc hng v ct AA u ra:mt ma trn lc ht t CA. Cc bc thc hin thut ton: Bc 1:t c nh 1 ct ca AA vo AC(chn ct 1). Bc 2:ln lt la chn v t n i ct cn li ca AA vo tng v tr sao cho s o lc ht chung AM l ln. Bc 3:sp xp th t hng ph hp vi v tr tng i vi cc ct.

4/20/201217Nhm 3 - Phm V Minh Hong Thut ton t nhm S o lc ht chung AM c nh nghanh sau: Cu ni(bond) gia hai thuc tnh Ax v Ay l: Khi AM c biu din nh sau: 4/20/201218Nhm 3 - Phm V Minh Hong 1 11 1( , )[ ( , ) ( , )]n ni j i j i ji jAM aff A A aff A A aff A A += == +z x z y1( , ) aff(A ,A )aff(A ,A )nx yzbond A A==( )3( )1( ) 21 11[ ( , ) ( , )]nj j j jjAM bond A A bond A A +== +Thut ton t nhm Xt n thuc tnh: AMAM Khi o lc ht chung ca n thuc tnh l: AMold=AM + AM + + ++ 1 2 1 1, ,... , , , ,...i i j j n AA A A AA A +1( , )i ibond A A,( , )i jbond A A( , )j ibond A A, 1( )j jbond AA +4/20/201219Nhm 3 - Phm V Minh Hong ( ) 41 111 11[ ( , ) ( , )][ ( , ) ( , )] 2* ( , )il l l llnl l l l i jl ibond A A bond A Abond A A bond A A bond A A += += += ++ + +Thut ton t nhm t thm mt thuc tnhvo gia vtrong ma trn t lc ht. Khi : AMnew = AM + AM+ +++ = AM+AM+2*+2* (5) V th ng gp thc cho s o i lc chung khi t thuc tnh Ak giaAi v Aj l: k Ai A j A( , )i kbondA A( , )k jbond A A,( )j kbond AA( , )i kbondA A( , )k jbond A A4/20/201220Nhm 3 Phm V Minh Hong ( )6( , )k ibond A A( , , )2* ( , ) 2* ( , ) 2* ( , )i k j new oldi k k j i jcont A A A AM AMbond A A bond A A bond A A= = + Thut ton t nhm V d 4:xt ma trn lc ht thuc tnh AA,tnh phn ng gp khi chuyn thuc tnh vo giav 4 A 1 A 2 A( ) ( ) ( )( )1 4 2 1 4 4 21 2ont , , 2* , 2* ,2* ,C bond bondbondAAA AA AAAA= +( )1 4, 35*0 0*70 35*2 0*72 70 bondAA= + + + =( )4 2, 0*0 70*75 2*5 72*70 10300 bondAA= + + + =( )1 2, 35*0 0*75 35*5 0*75 175 bondAA= + + + =( )1 4 2ont , , 2*35 2*10300 2*175 20495 CAAA= + =4/20/201221Nhm 3 V Trng Khanh Thut ton t nhm V d 5:Xt ma trn gi tr lc ht AA v d 3 1 2A A1 3 2A A A4 2 3 1A A A A123435 00 7535 50 70AAAA ( ( ( ( ( 123435 35 00 5 7235 42 50 2 70AAAA ( ( ( ( ( 123435 35 0 00 5 75 7035 42 5 30 2 70 72AAAA ( ( ( ( ( 132435 35 0 035 42 5 20 5 75 700 2 70 72AAAA ( ( ( ( ( 4/20/201222Nhm 3 - V Trng Khanh CA=CA=CA=CA=1 3 2 4A A A AThut ton phn mnh Mt s khi nim c bn: tp nh (top) TA v tp y (bottom) BA 4/20/201223Nhm 3 ng Vn Oanh Thut ton phn mnh K hiu: Q = {q1, q2, , qn}:tp cc ng dng. AQ(qi) = {Aj| use(qi, Aj) = 1} :tp cc thuc tnh c truy xut bi ng dng qi TQ = {qi | AQ(qi) TA}:Tp cc ng dng truy xut trn cc thuc tnh TA BQ = {qi | AQ(qi) BA}:Tp cc ng dng truy xut trn cc thuc tnh BA OQ = Tp cc ng dng truy xut trn c BA v TA __9/13/201124Nhm 3 - ng Vn Oanh Thut ton phn mnh nh ngha phng trnh chi ph nh sau: Phng trnh ti u ha xc nh im z sao cho ( ). ( )j i j iqi Q SjCO ref q acc qe =( ). ( )j i j iqi TQ SjCTQ ref q acc qe = ( ). ( )j i j iqi BQ SjCBQ ref q acc qe = ( ). ( )j i j iqi OQ SjCOQ ref q acc qe = ( )1 z n s s4/20/201225Nhm 3 - ng Vn Oanh 2* axi i iZ MCTQCBQ COQ= Thut ton PARTITION u vo: Ma trn i lc t CA, Quan h R, Ma trn s dng thuc tnh ref, ma trn tn s truy xut acc, K tp thuc tnh kha chnh ca R u ra: Tp cc mnh F BeginZ l v tr thuc tnh ct th nht Tnh CTQ1; tnh CBQ1; tnh COQ1; Best : = CTQ1 * CBB1 COQ1 *COQ1 For i := 2 to n do Begin Tnh CTQi; tnh CBQi; tnh COQi; iF z> best Then best :=z End; ;

End. 1: ( )TAR R K = [2: ( )BAR R K = [2 2: F R R = 2: *i i iZCTQCBQ COQ= 4/20/201226Nhm 3 ng Vn Oanh Thut ton phn mnh V d 6:xt 1 2 3 4A A A Aacc1(q1) = 12 acc2(q1) = 15acc3(q1) = 8 acc1(q2) = 5 acc2(q2) = 0 acc3(q2) = 0 acc1(q3) = 25 acc2(q3) = 20 acc3(q3) = 25 acc1(q4) = 2 acc2(q4) = 0 acc3(q4) = 0 132435 35 0 035 42 5 20 5 75 700 2 70 72AAAA ( ( ( ( ( 1 3 2 4A A A A4/20/201227Nhm 3 - Li Ngc Tuyn A=AA=12341 0 1 00 1 1 00 1 0 10 0 1 1qqqq ( ( ( ( ( Thut ton phn mnh v tr 1: CTQ1 = 35 CBQ1 =112 COQ1 = 35 z = 2695 v tr 2: CTQ2 = 42 CBQ2 = 77 COQ2 = 8 z = 3170 { }{ } { } { }1 31 2 4 2 3 4 2 4, , , , , , , , , TA TQ BQ OQqqq qqq qqAA= = = ={ }{ }{ }{ }11 1, , ,1 2 3 4, , , BQ TQ q OQ q qq q qTA A= = ==4/20/201228Nhm 3 - Li Ngc Tuyn Thut ton phn mnh v tr 3 CTQ3 = 112 CBQ3 = 72 COQ3 = 72 z = 2880 Ta chn v tr 2 lm im phn chia v ti v tr ny gi tr chi ph l cao nht. Nh vy chng ta c BRANCH1 = {A1, A3}v BRANCH2 ={A1, A2, A4} Tc l: BRANCH1 = {MACN,VON} v BRANCH2 = {MACN, TENCN, DDIEM} { }{ } { } { }1 3 21 2 3 4 3 4, , , , , , , , ,3 4, BQ TQ qqqq OQ qq q qTA AAA= = ==9/13/201129Nhm 3 - Li Ngc Tuyn Kt lun Phn mnh dc ni ring v phn mnh ni chung l mt phn trong qu trnh thit k cc h c s d liu phn tn,l cng vic u tin phi thc hin.vi mc ch to ra cc n v cp pht logic,sao cho chi ph thc hin truy vn thng tin l thp nht. Bi ton thit k h c s d liu phn tn l bi ton kh v phc tp,vn ti u cc h c s d liu phn tn cn c gii quyt v hin nay vn ang c i su nghin cu. 4/20/201230