Design notation

About design notation

1. DESIGN NOTATION PRESENTED BY M.RAMYA. M.sc (CS&IT), NADAR SARASWATHI COLLEGE OF ARTS & SCIENCE, THENI .

2. INTRODUCTION Good notation can clarify the interrelationships and interaction of interest. Three level of design specifications: External design specification Architectural design specification Detailed design specification

3. Notation used to specify the external characteristic , architectural structure and processing details of a software system include: D ataflow diagram Structure charts HIPO diagrams Procedure specification Pseudo code Structured flow charts

4. DATA-FLOW DIAGRAMS Dataflow diagrams are directed graphs in which the nodes specify processing activities and the arcs specify the data items transmitted between processing nodes. Dataflow diagram can be expressed using informal notation can be used to processing nodes , data sources , data sinks and data stores.

5. Dataflow diagrams are excellent communicating with customer during requirements and analysis. There are also used for representation of external and top level internal design specifications

6. Compute C Compute E Compute D Transform B Transform A Input A Input B Operator Input Y Reference Data X Operator Input Z Output E Output D B’ A’ C AN INFORMAL DATA FLOW DIAGRAM OR “BUBBLED CHART”

7. STRUCTURED CHARTS Structure chats are used to architectural design to document hierarchical structure , parameters and interconnection in a system . It differs from a flowchart in two ways: Structured chart has know decisions boxes. S equential ordering of tasks

8. A E D H C B G F 1 2 3 4 5 6 7 8 INDICATE REPETITION FORMAT OF A STRUCTURE

9. HIPO DIAGRAMS HIPO diagram(Hierarchy-process-input-output) were developed at IBM as design representation schemes for top-down software developed and external documentation aids for products. HIPO diagram contains a visual table of contents, a set of overview diagram and set detail diagrams , it contains of a tree structured .

10. PROCEDURE TEMPLATE The format of a procedure interface specification of architectural design , only information in level 1 need to supplied . The information on levels 2,3, and 4 can be included in successive steps. It provides initial architectural design , specification of side effects , exception handling , processing algorithms and data representation.

11. PSEUDO CODE NOTATION Pseudo code notation can be used in both the architectural and detailed design phases . The designer describes system characteristics using short , concise , that are structured by keywords such as If-Then-Else , While-Do and End. Pseudo code can replace flowcharts and reduce the amount of external documentations required to describe system.

12. STRUCTURED FLOWCHARTS Flowcharts means are specifying and documenting algorithmic detailed in a software system. Flowchart interoperate rectangular boxes for actions , diamond shaped boxes for decisions , directed arcs for interconnections for boxes. Single entry , single exit allows hierarchical nesting of structured flowchart to design in top-down fashion.

13. S1; S2; P S F T WHILE P DO S; BASIC FORMS FOR STRUCTURED FLOWCHARTS

14. DECISION TABLES Decision tables can be used to specify complex decision logic in a high level software specification. There are useful for specifying algorithmic logic during detailed design. Several preprocessor packages are available to translate decision tables into COBOL.

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