SDC – SDLC integration

SA/SD SA/SD technique draws heavily from the following methodologies: Constantine and Yourdon's methodology DeMarco and Yourdon's methodology SA/SD technique can be used to perform high-level design.

Definitions Software Development Cycle System Development Life Cycle Analyse detailed requirements Preliminary Analysis Design data and algorithms Analysis Code data structures and instructions Design Debug syntax and logic errors Implementation Test to meet specifications Evaluation Document internally and externally Maintenance Implement and test with live data Evaluate performance of the program

SA/SD methodology consists of two distinct activities: Structured Analysis (SA) Structured Design (SD) During structured analysis: functional decomposition takes place. During structured design: module structure is formalized

DFD (SDLC) = STRUCTURE CHART (SDC) DFD = Structure Chart DFD (SDLC) = STRUCTURE CHART (SDC)

Consider the following DFD Main Validating Account Processing Transaction

Structured Analysis v Structured Design Data Flow Diagrams of Programs – Structured Analysis (SA) Structured design requires that data flow diagrams (DFDs) first be drawn for the program. Processes appearing on the logical, elementary DFDs may represent modules on a structure chart. Logical DFDs need to be revised to show more detail in order to be used by programmers The following revisions may be necessary: Processes appearing on the DFD should do only one function. Processes need to be added to handle data access and maintenance. DFDs must be revised to include editing and error handling processes, and processes to implement internal controls.

Structured analysis Transforms a textual problem description into a graphic model. done using data flow diagrams (DFDs). DFDs graphically represent the results of structured analysis.

Design Some tasks Module development Identify variables IPOS Pseudocode Flow charts Structure diagrams (parameters/modules/functions) Testing (desk checks/trace tables) – syntax/logic/run-time errors Internal documentation External documentation

Structured Design All the functions represented in the DFD: mapped to a module structure (structure chart). The module structure: also called as the software architecture:

Software Development Cycle Tasks Analyse detailed requirements IPOS/DFD’s Design data and algorithms Identify variables/ types/ structures/ pseudocode/ structure charts to show modules Code data structures and instructions Into preferred language Debug syntax and logic errors Logic errors: Desk check, trace table (logic error), Syntax Errors: use a compiler rather than interpreting program as interpreters message may not differentiate between syntax and other errors. Runtime errors could be a logic error ie poor programming or a software install problem or a hardware issue. Test to meet specifications Check that any scenarios provided can be fixed in software Document internally and externally Comments and manuals Implement and test with live data Again a trace at the margins of limits. Evaluate performance of the program Hardware requirements, live testing/using, surveys, benchmarks