bai giang mo hinh dfd.pdf

8/2/2019 bai giang mo hinh dfd.pdf

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Chng 4

PHN TCH H THNG:

M hnh lung(dng) d liu


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Cc khi nim Thit k mc khi nim(Conceptual design) M hnh d liu (Data models) M hnh chc nng(Functional Models)

M hnh d liu(Data models): L k thut t chc v h thng d liu trn ti

liu.(organizing and documenting system's data)

M hnh chc nng(Functional Models) nh ra cu trc ca cc chc nng qun l gipcho h thng qun l thc hin cc ng dngqun l


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Cc khi nim M hnh x l:is a technique for organizing

and documenting a system's processes,

inputs, outputs and data stores. M hnh x l phn mm l mt m t tru

tng ca cc qu trnh x l.

Cc m hnh h thng l tp cc chc nng

tng tccung cp cc chc nng x l.


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M hnh x l (DFD) DFD(Data flow diagram- m hnh lung d

liu) l mt trong nhng cng c hu hiu

ca giai on phn tch(is one of the toolsused in the analysis phase).

S dng DFD biu din mt cch linhhot cc thc th ngoi, cc chc nng,

lung d liu v cc kho d liu (p74)


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M hnh x l (DFD) -Cc khi

nim DFD lun l(logic) din t h thng lm g m

khng din t iu lm nh th no, tp

trung vo cc hot ng ca doanh nghipm khng tp trung vo h thng s todng ra sao.

DFD vt l (physical) din t h thng s

c thc hin nh th no, trong cpn phn cng, phn mm, tp tin v conngi.


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M hnh x l (DFD)

Cng dng DFD: din t hot ng ca h thng hin

hnh (da trn xc nh yu cu)

DFD: l phng tin trao i gia ngiphn tch v ngi s dng

DFD: xy dng ti liu c t thit k x l.


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M hnh x l (DFD) Cc k

hiu

Process

Data flow

Data store

External Entity


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M hnh x l (DFD) -Cc khi

nim Modules: Mt h thng ln (large system) bao gm cc h

thng con(subsystems

) c lp(independent

) m c thkt ni vi nhau.

Phn chia modules ph thuc vo: Size

Shared use


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M hnh x l (DFD) - Process Processes: T chc tp cc hot ng chuyn t u vo

thnh u ra Phn tch yu cu Thit k kin trc Tch hp h thng

Mi process phi c t tn theo dng:

Tn h thng Tn h thng con Mt ng t ///xem thm p76


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M hnh x l (DFD) Data Flow

Data flows : l thnh phn th hin mu d liura/vo ca x l (represents the input (or output) of data to (orfrom) a process ("data in motion")).

Data flows: ch l d liu (only data), khng l iu khin(not control). u mi tn ch im n ca d liu. Data flows:

Phi bt u hay kt thc mt process.

T kho d liu n x l hay ngc li T tc nhn ngoi n x l hay ngc li Mi dng d liu phi c mt tn duy nht bng danh

t th hin phn t d liu hay cu trc d liu


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M hnh x l (DFD) Data Store

Data store(Kho d liu): l ni cha d liu,l cc bng c xc nh trong qu trnh

phn tch thit k d liu (an "inventory" of data ). Dng d liu hng v kho d liu dng

din t hot ng: thm, sa hay xa d liu.

Dng d liu ri kho d liu: din t hot

ng c d liu trong kho.


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M hnh x l (DFD) ExternalEntities

Tc nhn ngoi(External Entities) : l thnh phnnm ngoi h thng c quan h cung cp

hay nhn d liu t thnh phn x l. Mi tc nhn phi c t tn bng danh

t.


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V d: gi s vn qun l

n hng c m hnh ER sau:


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Vi m hnh qun l trn, gi s c form nhp liui din cho thnh phn x l ca vic thm mi

mt n hng c dng:


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Logic hot ng ca thnh phn x l thm min hng c din t bng cc s DFD cp

0 nh hnh:


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Logic hot ng ca thnh phn x l thm min hng c din t bng cc s DFD cp1:

M khch hng

1.1

Kim tra mkhch hng

Ngy

n hng

M khch

hng

D3 n hang

M khch

hng mi

1.3

To s nhng

1.2

Thm khch

hng

Khch hng

Tn khch hng+

a ch+S in thoi

M khch

hng

1.4

nhp chi titn hng

S n hng

M hng +

s lng

D4 Dong n hang

n hng

D1 Mat hang

D2 Khach hang


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Cc cp ca s DFD DFD din t h thng t tng qut n chi

tit

S mc chi tit c phn r t mctng qut hn: DFD ng cnh

DFD cp 0

DFD cp con (1,2,3,.) Mi s DFD cha ti a 9 x l


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Cc cp ca s DFD Mi x l ca DFD c trn 4 dng d liu

vo ra phi c phn r thnh s DFD

con. x l khng th phn r phi c thit k

x l chi tit bng cc cu lnh, s thutgii, bng quyt nh, cy quyt nh


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DFD ng cnh

(context diagram) Din t ton b h thng bng mt x l

DFD ng cnh l s mc tng qut

nht DFD ng cnh xc nh phm vi ca h

thng

DFD ng cnh khng c kho d liu


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DFD ng cnh

(context diagram)- V d


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DFD cp 0 (level 0-DFD) Gm cc x l p ng li cc s kin

c pht sinh t cc tc nhn ngoi h

thng DFD cp 0 chnh l s phn r t x l

ca s ng cnh

DFD cp 0 phi din t tt c cc kho d liu

v dng d liu vo ra c lin quan n xl.


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DFD cp 0 (level 0-DFD)- V d

Khach hang

1

Thmn hngD4 Dong n hang

D1 Mat hang

D3 n hang

D2 Khach hang

2

Cap nhatmat hang

BO PHANQUAN LY

Thong tinmat hang

n hng

Thng tin vkhch hng+

hng mua

3

Cap nhatmat hang

Thng tin vkhch hng

4To bo co trgi hng bn

Ch tiubo co

Bo co

tr gi hng bng

D3 n hang

D4 Dong n hang


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DFD cp con Hnh thnh t vic phn r (decomposition )

x l c trn 4 dng d liu vo ra.

Dng d liu vo ra ca s phi cn bng(balancing) vi dng d liu ca x l cphn r.


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DFD cp con- v d

D1 Mat hang

Sn hng

1.4.1

Tm m t, vt,n gi camt hng

Khch hng

S lngM hng

hay enter

D4 Dong n hang

1.4.2

Tnh stt,

thnh tin,tng cng

M hng+

n gi

nhng

1.4.3

To nhng

Sn hng

enter

D3 n hang

D2 Khach hang


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DFD- Cc qui tc khi v Process(o x ly)

Phai chuyen o x ly ch co mot dong d lieu i ra thanh tacnhan cung cap d lieu.

Phai chuyen o x ly ch co mot dong d lieu i vao thanh tacnhan nhan d lieu.

Dung ong t e at ten cho o x ly.

Data store(kho d lieu)

Dong d lieu khong the la cau noi gia hai kho d lieu. Dong d lieu khong the la cau noi gia tac nhan va kho d

lieu.

Dung danh t e at ten cho kho d lieu.


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DFD- Cc qui tc khi v External Entities(tac nhan) Dong d lieu khong the la cau noi gia hai tac nhan Dung danh t e at ten cho tac nhan.

Data flows(dong d lieu) Dong d lieu khong the la cau noi cua mot x ly. Dong d lieu vao kho d lieu mang y ngha cap nhat

(them, sa, xoa) Dong d lieu ra khoi kho d lieu mang y ngha tham

khao. Dung danh t e at ten cho dong d lieu.


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DFD- Cc qui t

c khi v

Cac ky hieu lap lai: e tranh cac dong d lieu giao nhau, tren s

o DFD, ta co the lap lai cac kho d lieu, cactac nhan

Cac phan t lap lai nay c anh daubang cach ve them ng ke oi doccho kho d lieu va ng ke cheo chotac nhan .


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Cc quy tc khi v Mt qu trnh phi lun c lung d liu vo v ra Khng cn c mt lung d liu (m khng c s

bin i) lin kt vi mt qu trnh (v hot ng nhvy l v gi tr)

Cc qu trnh cha v cc qu trnh con tng ngca n phi c cc lung d liu vo ra ging nhau(nhng cc qu trnh con c th c lung d liuca ring n)

Cc lung d liu khng th t phn tch c

Mt gi d liu c th gm nhiu phn t d liuc truyn i ng thi ti cng mt ch Khng c s dng mi tn hai chiu v lung vo

(cp nht) v lung ra (trch thng tin) ca mt khod liu mang ni dung thng tin khc nhau

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bai giang mo hinh dfd.pdf