CSA 1010 Principles of Structured Design

Transcription

1 CSA 1010 Principles f Structured Design ECDs Ntes and Examples (rle 1) Frankie Inguanez * (rle 2) University f Malta (effect) (effect)

2 Lecture Schedule ECDs Overview & Aims ECDs Ntatins Steps t designing ECDs Examples Questins 2

3 Effect Crrespndence Diagrams ECDs are used t analyse the effects frm the events perspective. ECDs fllw ELHs. The aim is t: Illustrate which entities are affected by a given event. T define hw the effects n these different entities crrespnd with each ther. T prvide us with update access paths fr use in lgical design. 3

4 ECDs Ntatins - An entity is an bject that acts and is acted n by the system. Entities are represented as a runded rectangle. 4

5 ECDs Ntatins Simultaneus Effects When an effect causes an entity t take mre than ne rle simultaneusly we encapsulate the rles in questin in a rectangle. (rle 1) (rle 2) 5

6 ECDs Ntatins Optinal Effect A small '' is added t the entity frm which tw r mre mutually exclusive effects may be resulted due t an effect. (effect) (effect) 6

7 ECDs Ntatins - Iteratin An asterisk is added t an entity that is affected multiple times. * 7

8 ECDs Ntatins One t One Crrespndence When tw entities are updated at the same time they are cnnected by a duble-headed arrw. 8

9 ECDs Steps t Designing ECDs (i) Fllwing are the 8 steps required fr building an ECDs: 1.Identify all entities which are affected by the event (by lking at the effect bxes in their ELHs), and draw a rund-crnered bx fr each ne. 2.Identify simultaneus effects fr the event, and draw a separate bx fr each entity rle cncerned. 3.Identify where an event affects an entity in ne r mre mutually exclusive ways, and add the effects as ptins bellw the relevant entity bx. 9

10 ECDs Steps t designing ECDs (ii) 4.Identify entities iteratively affected by the event, draw an iteratin bx fr each ne. 5.Identify effects which are in ne-t-ne crrespndence, and cnnect the affected entities with a duble-headed arrw. Fr each affected ccurrence f this entity, is there a directly related ccurrence in any f the ther entities that is als affected by the event? Fr each affected ccurrence f this entity, is there a directly related set f ccurrences in any f the ther entities that is als affected by the event? 10

11 ECDs - Steps t designing ECDs (iii) 6.If an entity is affected in mre than ne iterative way by an event, then the tw iteratin structures shuld be merged int either a selectin f iteratins, r an iteratin f selectins. 8.Add nn-updated entities T prvide access t entities that are needed t prvide utput data (pssibly fr event cnfirmatin). T link tgether tw sets f affected entities which are nt directly cnnected via relatinship n the LDS. 9.List the input data (r 'event data') under the entry pint fr the event. 11

12 ECDs Example 1 (i) Cnsider an Arrange event Identify all entities which are affected by the event:, Line, Slt and Purchase Order Slt Line P.O. Line 12

13 ECDs Example 1 (ii) Identify simultaneus effects fr the event, and draw a separate bx fr each entity rle cncerned. N/A 13

14 ECDs Example 1 (iii) Identity where an event affects an entity in ne r mre mutually exclusive ways, and add the effects as ptins belw the relevant entity bx. Existing New 14

15 ECDs Example 1 (iv) Identify entities iteratively affected by the event, and draw an iteratin bx fr each ne. Lines Existing New Line * Slts Slt * Purchase Order Line 15

16 ECDs Example 1 (v) Identify effects which are in ne-t-ne crrespndence and cnnect the affected entities with a duble-headed arrw. Lines Existing New Line * Slts Slt * Purchase Order Line 16

17 ECDs Example 1 (vi) If an entity is affected in mre than ne iterative way by an event, then the tw iteratin structures shuld be merged int either a selectin f iteratins, r an iteratin f selectins. N/A 17

18 ECDs Example 1 (vii) Add nn-updated entities Lines Existing New Line * Slts Slt * Purchase Order Line Prduct

19 ECDs Example 1 (viii) List the input data under the entry pint fr the event. ID, Slide ID., P.Order N., P.O Line N., Quantity,etc

20 ECDs Additinal Examples (i) If an entity is affected in mre than ne iterative way by an event then the tw iteratin structures shuld be merged int either a selectin f iteratins, r an iteratin f selectins. Stcks Stcks Stck * Stck * (Type A) (Type B)

21 ECDs Additinal Examples (ii) Stcks Stcks Stcks * Type A Type B Type A Type B Type A * Type B *

22 References Practical SSADM Versin 4 - A Cmplete Tutrial Guide Practical SSADM Versin 4 - A Cmplete By Philip L Weaver Smartdraw 22

23 Questins? Nw is yur time fr questins! 23