1 STRUCTURE CHARTS An Example The Registration System

1 STRUCTURE CHARTS An Example: The Registration System

2 registration system 0 conf reg+ conf invoice reg+ invoice read & check registration 1 compute registration 2 produce registration outputs 3

3 registration system 0 conf reg+ conf invoice reg+ invoice read & check registration 1 compute registration 2 produce registration outputs 3

4 read & check registration 1 reg_i error_reason reg_flag read registration 1. 1 check registration 1. 2 error-handler registration 1. 3 error-msg registration CRT

5 registration system 0 conf reg+ conf invoice reg+ invoice read & check registration 1 compute registration 2 produce registration outputs 3

6 compute registration 2 reg+ invoice prepare invoice 2. 1 conf accept registration 2. 2 reg_profile prices reg_info registration db

7 registration system 0 conf reg+ conf invoice reg+ invoice read & check registration 1 compute registration 2 produce registration outputs 3

8 produce registration outputs 3 invoice print invoice 3. 1 conf write confirmation 3. 2 invoice_prt PRT conf_msg CRT

9 0 2 1 1. 2 1. 3 crt input-driven 2. 1 3 2. 2 db center of transformation 3. 1 3. 2 prt crt output-driven

10 Remember during Composition • a module is a unit of execution • invocation between modules is directed • data flows and control flows must follow the invocation hierarchy • data stores, devices, and external systems are typically at the lowest level of your SC • sequence of execution depends on

11 Suggestions for a Good Style • have a balanced system: input => processing => output • think in terms of stepwise-refinement • module encapsulates a single function • limit the use of control flows • reflect the sequence of execution in

12 DFD <===> SC ? ? A Structure Chart is derived from a Data Flow Diagram and is a mapping and refinement of the DFD. ==> Algorithms? / Heuristics?

13 End of Section 3 c coming up: DFDs <==> SCs