CHNG 5:

LU DNG D LIU (Data Flow Diagram DFD)

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Gii thiu: Thnh Phn X LMCDLm r mi quan h v ng ngha gia cc d liu Nhng khng th hin cch thc cc d liu ny s c to ra, thay i v lun chuyn trong h thng.

Gii php: xy dng thnh phn x l DLTip cn c in. Tip cn hin iTheo kiu Bc M: m hnh DFD (c 2 mc: mc quan nim v mc vt l) Theo kiu chu u: m hnh MERISE (c 3 mc: mc quan nim, mc logic v mc vt l)2

Lu Dng D Liu (DFD)DFD biu din s kt ni gia cc hot ng ca h thng, thng qua vic trao i d liu khi h thng hot ng . Lu dng d liu phi th hin c:X l no ph thuc vo cc x l no D liu cn cho mi x l

Phng php to DFD: phn r cc hot ng chi tit dn n khi c th chuyn cho ngi lp trnh trin khai.3

Mc ch ca mt DFDMt DFD s m t: Cc qu trnh x l bn trong h thng. Cc kho lu tr h tr cho cc thao tc ca h thng. Cc dng thng tin trong h thng. Ranh gii ca h thng. S giao tip vi cc thc th bn ngoi.

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Cc khi nim

Qu trnh x l/ x l Dng d liu: D liu vo & D liu ra Ngun / ch Kho d liu

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Qu trnh x l / x lGm nhiu thao tc trong mt lnh vc no . Mt x l tng ng vi mt qu trnh x l trong th gii thc. Tn x l thng l mt ng t K hiu1 Bn hng Tn qu trnh x l S th t qu trnh x l

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Dng D LiuD liu vo: Cc i tng tham gia vo qu trnh x l, l gi tr ca cc thuc tnh ca cc i tng . D liu ra: L kt qu ca mt qu trnh x l trong th gii thc, thng l mt vt chng no (danh sch, ha n,) DL ra ca x l ny c th l DL vo ca x l khc K hiu dng d liuD liu vo D liu vo D liu vo

STT x l Tn x l

D liu ra D liu ra D liu ra7

Ngun / chL cc thc th bn ngoi h thng:Ngun tc ng vo h thng lm cho h thng khi to cc qu trnh x l ch l i tng m h thng phi cung cp cho

K hiu

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Ngun/chMt ngun/ch c th l:Mt t chc khc hay mt n v khc ca t chc gi d liu hoc nhn thng tin t h thng ang c phn tch. VD: b phn cung cp hng. Mt ngi bn trong hoc bn ngoi n v kinh doanh h tr bi h thng ang phn tch v tng tc vi h thng. VD: khch hng. Mt h thng thng tin khc c trao i thng tin vi h thng ang c phn tch.

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Kho D LiuL ni cha d liu m qu trnh x l cn tham kho hoc cn lu tr li sau qu trnh x l. K hiu:Kho d lieu hoac Kho d lieu

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Kt hp cc khi nim trn 1 x lNGUN < d liu vo> < DL t x l khc> < DL t x l khc> STT qu trnh x l Tn qu trnh x l < d liu ra> CH

< DL n XL khc> < DL n XL khc> < d liu ra> D1 Kho d liu 1

< d liu ra> < d liu vo> D2 Kho d liu 2

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CC CP ca DFD

Vic phn tch thnh phn x l bng DFD l phng php phn tch i xung (topdown), t tng qut n chi tit.

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DFD Cp 0L cp thp nht hay cn gi l s ng cnh (context diagram) Trong ton b h thng l mt qu trnh x l. K hiu:NGUN 1 < d liu vo> NGUN 2 < DL vo> < d liu vo> 0 < d liu ra> < d liu ra> < d liu ra> CH 1

CH 213

VD: DFD cp 0 ca HT t thc nKHCH HNG H ca KH Ha nHT T THC AN

NH BP n t thc an

Cc bo co qun l BAN QUN L NH HNG

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DFD Cp nCc cp cao hn c c bng cch chi tit ha tng x l ca cp trc. Cp n c c bng cch phn r mi x l cp n-1 thnh nhiu x l cp n. Vic dng mc no l ty h thng, thng l ti mc m mi ngi u chp nhn trong vic nhn thc v thnh phn x l ca h thng.

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VD: DFD cp 1 ca HT t thc nKHCH HNG H ca KHHa nNhn & bin di H Hng Cp nht hng bn D liu hng bn cp nht Hng bn S lung hng bn mi ngy To BC qun l bn

NH BPn t thc an

D liu v kho Cp nht kho hng D liu kho hng cp nht Kho hng S lung hng xut kho mi ngy Cc bo co qun l

BAN QUN L NH HNG16

Cc lut v DFD (1)Cc lut c bn m tt c cc DFD phi tun theoD liu vo v d liu ra ca mt x l phi lun lun khc nhau Cc x l, cc kho d liu v cc ngun/ ch phi c mt tn duy nhtTuy nhin, lm cho s khng b ri, ta c th v lp li cc kho d liu v cc ngun/ch trn mt s .

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Cc lut v DFD (2) x lA. Khng c x l no ch c d liu ra (php l?) B. Khng c x l no ch c d liu vo (l en?) C. Tn ca mt x l phi l ng t Kho d liuD. D liu khng th di chuyn trc tip t mt kho ny sang mt kho khc E. D liu khng th di chuyn trc tip t mt ngun vo mt kho F. D liu khng th di chuyn trc tip t mt kho vo mt ch G. Tn kho d liu phi l mt danh t18

Cc lut v DFD (3)Ngun/chH. D liu khng th di chuyn trc tip t mt ngun sang mt ch I. Tn ca mt ngun/ch l mt danh t

Dng d liuJ. Mt dng d liu ch c mt hng K. Mt k hiu phn nhnh cho bit chnh xc cng mt d liu xut ra t mt ni v i n 2 hay nhiu x l hay ngun/ch khc AA19

Cc lut v DFD (4)A

Dng d liu (tip theo) A L. Mt im kt th hin chnh xc cng mt d liu

n t bt k hai hay nhiu x l, kho d liu hay ngun/ch v i n cng mt ni. M. Mt dng d liu khng th i tr li chnh x l xut ra n mt cch trc tip N. Mt dng d liu i n mt kho d liu c ngha y l mt hot ng cp nht O. Mt dng d liu i ra t mt kho d liu c ngha y l mt hot ng truy xut hay s dng d liu P. Mt dng d liu phi c mt nhn l danh t20

Cn bng cc DFDKhi phn r mt DFD, ta phi bo ton cc dng d liu vo v cc dng d liu ra khi mt x l mc k tip. iu ny c gi l cn bng. V d DFD mc 0 v mc 1 ca HT t thc n cp trn

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VD: Tp cc DFD khng cn bng

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VD: Tp cc DFD cn bng

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Cc nguyn tc dng phn r DFDKhi mi x l l mt quyt nh, mt tnh ton hay mt thao tc trn CSDL (thm, sa, xo). Khi mi kho d liu i din cho mt thc th. Khi ngi dng ca h thng khng quan tm n cc chi tit nh hn na. Khi mi dng d liu khng cn phi chia ra nh hn th hin chng c x l khc nhau. Khi bn tin rng c mt x l cho mi chn la ca cc tu chn cp thp nht trn menu h thng.24

c t x lL nhng hng dn, gii thch lm r ni dung ca x l. S dng cc cng c sau y m t:Vn bn c cu trc M gi Bng quyt nh Cy quyt nh Lu

Tham kho nh ngha cc cng c ny trong Gtr trang 25-29

Yu cu: phi nu c trnh t logic cc thao tc, tnh cht mi thao tc V d: c t x l Lp ha n bn hng25

Mi quan h gia MCD v DFD c t cc x l, ta xt mi quan h gia MCD v DFD. Mi x l thuc loi ghi nhn d liu c mi lin quan ti mt s con trong m hnh MCD. Ta c th lm r mi quan h ny bng cch v mt ng cong khp kn bao quanh cc thc th lin quan n mt x l. VD: xem GT

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Cc bc pht trin DFDPht trin dng top-down 1. Lit k danh sch cc cng vic m h thng s thc hin, t xc nh cc ngun/ch, dng d liu, x l, kho d liu 2. To s mc ng cnh (context diagram): Biu din giao tip gia h thng v cc ngun/ch. Ch : Trong s ng cnh khng c kho d liu hoc bt k x l chi tit no. 3. V cc s mc tip theo 4. Kim tra cc lut v cch t tn27

V d: HT phn phi a CDCp 0Thanh vien Hoa don Don dat hang 1 He thong phan phoi dia CD DVD Hoa don va DS phan phoi Bo phan phan phoi hang

Mau DK TV da dien tt

Khach Hang

Mau DK Thanh vien

Mau DK TV da dien tt khong hop le

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V d: HT phn phi a CDMau DK TV da dien tt Khach hang 1 Dang ky TV Mau DK TV hop le 2

3 Cap nhat TV Thanh vien da cap nhat Danh muc Thanh vien

Thong tin DK TV Kiem tra tinh trang thanh vien Mau DK TV khong hop le Mau DK TV Don dat hang DDH cua Thanh vien

Thong tin Thanh vien

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4 Thanh vien Kiem tra tinh trang hang hoa Hang hoa DDH da kiem tra 5 Cap nhat Don hang 2 Danh muc Hang hoa

Hoa don

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Danh muc DDH

Thong tin DDH

DDH chua phan phoi

Bo phan phan phoi hang

6 In Hoa don va Hoa don va DSach chuyen hang DS chuyen hang

Cp 129

Context DFD Example

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