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PROCESS SPECIFICATIONS for DFDs

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holleb
19 diapositives · 878 Views · Jul 13, 2014

PROCESS SPECIFICATIONS for DFDs. Concepts and Examples. Process Specification. part of the specifications for a complete Dataflow Analysis (DFD) OOAD model SADT etc. Process Specification for a DFD. specifies process “bubbles” in a DFD NOT sources and sinks

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  1. PROCESS SPECIFICATIONS for DFDs Concepts and Examples

  2. Process Specification • part of the specifications for a complete • Dataflow Analysis (DFD) • OOAD model • SADT • etc.

  3. Process Specification for a DFD • specifies process “bubbles” in a DFD • NOT sources and sinks • must be consistent with DFD • specification compatible with diagram • must be complete with regard to the DFD • consists of • process decomposition (diagrams) • process description

  4. Process Description • (see also IEEE 830-1984) • name (and aliases) • informal description • inputs (see DFD & data dictionary) • outputs (see DFD & data dictionary) • processing (semi-formal) • related processes, sources and sinks

  5. Example: Patient Monitoring System

  6. Read & Check Query • name: read & check query (RCQ) • description: Reads query statements from the physician’s terminal interface, brings them into internal format, checks correctness and completeness, and handles error situations. Transaction oriented. Communicates with user interface.

  7. Read & Check Query • inputs: • Query • from: physician terminal • (external source)

  8. Read & Check Query • outputs: • Query + • to: process request • (system internal process) • Query - • to: physician terminal • (external source) • comment: needs further elaboration

  9. Read & Check Query • related processes, sources and sinks: • depends on: • user interface design for physician terminal • is-part-of (super-ordinate process): • Patient Information System

  10. Read & Check Query • related processes, sources and sinks: • is-decomposed-into (sub-ordinate proc.): • read query • check query • error handling for query

  11. (Semi-) Formal Specification? • PDL - Program Design Language • see Caine, Farber, and Gordon • “pseudo-code”, structured English • English embedded within programming language syntax • close to flowcharts

  12. Specifying Processes in DFDs • Structured English • Decision Trees • Decision Tables => see the example SRS on the course webpage => read A.Davis’ book (see Welcome Letter)

  13. STOP HEREWe will come back at design level!

  14. PDL • modelling basic control - a block: BEGIN block-name statements END block-name PROCESS process-name process description END process-name

  15. PDL • modelling basic control - a condition: IF condition THEN block ELSE block ENDIF Remark: There is a CASE construct.

  16. PDL • modelling basic control - a iteration: DO-WHILE condition block ENDDO Remark: There are REPEAT and DO-FOR constructs.

  17. Read & Check Query - PDL PROCESS read&check_query event: query window is activated; initialise interface (query window); DO WHILE user keeps interface active => query call read_query => query-i; call check_query => query_error_info or query+; IF query_error_info THEN call error_handling_for_query => query- ENDIF ENDDO END.

  18. End of Section 2f coming up: software design

  19. (Semi-) Formal Specification? • PDL - Program Design Language • see Caine, Farber, and Gordon • “pseudo-code”, structured English • English embedded within programming language syntax • close to flowcharts