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第四章 关 系. 4.1 二元关系 4.2 关系运算 4.3 关系类型. 退出. 4.1 二元关系. 二元关系,这里是指集合中两个元素之间的关系。 1 .基本概念 定义4.1.1 给定任意集合 A 和 B , 若 R A B , 则称 R 为从 A 到 B 的二元关系,特别在 A = B 时,称 R 为 A 上的二元关系。. 可见, R 是有序对的集合。若< x , y > R , 则也表为 xRy , 即< x , y > R xRy 。 - PowerPoint PPT Presentation
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4.1 4.2 4.3
4.1 14.1.1 ABRABRABA=BRA
RRxRyRxRyR=RABR=ABRABA=BAR=AAAR={|xA}AIA
nS AiS AinA1=A2==AnSAn
4.1.2 RABD(R)={x|(y)(xRy)}R(R)={y|(x)(xRy)}F(R)=D(R)+R(R)D(R)R(R)F(R)RD(R)AR(R)B
RSRSRSR-SRSRx(RS)yxRyxSyx(RS)yxRyxSyx(R-S)yxRyxSyx(RS)yxRyxSyxR yxRy
24.1.3 A={a1,a2,,am}B={b1,b2,,bn}RAB 1 aiRbjrij= 0 MR=(rij)mnR
RMRMRRARAaiajaiajRaiajaiajRaiRGR
4.1.6 RAAAxyxRyyRxRAR(x)(y)(x,yAxRyyRx)R
4.1.7 RAAAxyxRyyRxx=yRAR(x)(y)(x,yAxRyyRxx=y)Rx=yRx=y
4.1.8 RAAAx, y, zxRyyRxxRzRAR(x)(y)(z)(x,y,zAxRyyRzxRz)R
ARMR0GRARMRGR
ARMR1GRARMRrij=rjk=1rik=1GRMRGRR
4.1.1 RAARR
4.2 R, SABRSRSRR-SAB
14.2.1 RABSBCRSACRSRSRSRSRSRS={|(b)(bBaRbbSc)}
4.2.1 RAARIA=IAR=R4.2.2 RABS,TBCWCD R(ST)=RSRT R(ST) RSRT (ST)W=SWTW (ST)W SWTW
4.2.3 RABSBCTCD(RS)T=R(ST)
24.2.2 RAnNRnRn(1) R0=IA(2) Rn+1=RnR4.2.4 RAAm, nN(1) RmRn=Rm+n(2) (Rm)n=Rmn
34.2.3 RABRBAR-1R-1RR-1RR-1={|R} xRyy R-1x-1=(AB)-1=BA
4.2.7 RABSBC(RS)-1=S-1R-14.2.8 RSAB (R-1)-1=R D(R-1)=R(R)R(R-1)=D(R) (RS)-1= R-1S-1 (RS)-1= R-1S-1 (R-S)-1= R-1-S-1 RSR-1S-1
4.2.9 RAARR=R-1
4
4.2.4 RARR1 R1 RR1 R2RR2R1R2Rr(R)s(R)t(R)
4.2.10 RAA Riff r(R)=R R iff s(R)=R Riff t(R)=R
R4.2.4RR1r(R)=Rr(R)=R4.2.4RRR
4.2.11 RAA r(R)=RIA s(R)=RR-1 t(R)=
4.2.12 RAA|A|=nt(R)= 4.2.13 RAA rs(R)=sr(R) rt(R)=tr(R) st(R)ts(R)
5RSABTBCMR=(aij)mnMS=(bij)mnMT=(cij)npdij
MRS=MRMSdij=aijbij 1im1jn MRS=MRMS dij=aijbij 1im1jn dij=aji 1im1jn
MR-S=MR dij=aij(bij) 1im1jn =MRT dij=aij 1im1jn MRT=MRMT dij= (aikckj) 1im1jn
4.3 14.3.1 RARRARaRbababRabbaab
mZ
4.3.2 ma, bZma-b=kmabmab(mod m)4.3.1 mAZR
4.3.3 RAaA[a]R={x|xAaRx}[a]RaRa[a][a]Ra[a]R
4.3.2 RA a, bAaRb[a]=[b] a, bAaRb[a][b]= =AA
4.3.4 RAA/R={[a]R|aA}A/RARA/RR
4.3.5 AB={A1,A2,,An}AiAiAj=ij =ABABAA/RAAB={A1,A2,,An}AR
R= R={|(Ai)(AiBa, bAi)}RAA/RBAA
24.3.6 RARRARRaRbab
RAR-1ARR-1abababABABAB363|636
4.3.9 BAbB (x)(xBbx)bB (x)(xBxb)bB (x)(bxxb)bB (x)(bxbx)bB
BBBBBB
4.3.10 BAbA (x)(xBbx)bB (x)(xBxb)bB
bBbbbbBglb bBbbbbBlub
BBBBBBBB
abbaab
4.3.11 a,bAaba,bAabbaA
4.3.12 AA
34.3.13 RARRA
4.3.14 AB={A1,A2,,Am} =ABAAAA
4.3.15 RACACa,baRbCRAaRA
4.3.16 RACRA-CCCRCR
4.3.17 RAACR(A)R
1
1
4.3.3 A{A1,A2,,Am}R=
4.3.4 ARCR(A) ARCR(A)4.3.3CR(A)ARCR(A)
4.3.5 RARIA
4.3.6 RA Rr(R)=RIA RR-IA