"Structured Analysis and Design - Download as PowerPoint"
Structured Analysis and Design Dr. Jo Hartley Room N404 Analysis and Design Module Syllabus Introduction to real-time Organising the model systems and Essential State-transition diagrams model and Data transformation Data transformations and specification Data flows, Data stores, Conservation of Data and Implementation model and Synchronous Data rules Data dictionary Control transformations, Processor level, Task level Event and Control flows, and Module level and Event stores Lecture 7. Structured Analysis and Design Data transformation specifications • When • How Using Yourdon for Data transformation specifications When to use data transformation specifications General rule: • When the data transformation converts one input into one output and • When the transformation can be fully described by text of less than one page How do we specify May use: • Narrative text • Flowcharts • Functions in tabular/graphic form • Decision tables/trees Structured Ordinary Language Remove: Include: • adjectives • inputs/outputs • get (for input flows) • adverbs • issue (for output flows) • selection • compound sentences • if, then, else, end if • asides • iteration • for each, do, end for • footnotes • while, do, end while • repeat, until • create, find, obtain, store, delete, calculate Using Yourdon for Data transformation specifications Click on Data Transformation Select child diagram | PSPEC | Open Add Narrative text using inputs and outputs Essential Modelling Heuristics Essential model - describes those things that a system must do to be successful, regardless of the technology. A model of the environment should be incorporated, ensuring that all relevant info. about the environment is captured. The behavioural model describes a mapping of elements from the environment into the model. The Essential Model The Essential Model Environmental model Behavioural model Describes environment in Describes behaviour of system which system is found in response to external events Context diagram External Event list Transformation schema Data schema Describes boundary between Describes events to Describes transformations Describes necessary system and environment which system responds that the system makes information within the system The Implementation Model Implementation model Processor model Task model Module model Shows decisions made about Shows decisions made Shows decisions made about processors and interfaces about tasks and interfaces allocation of essential model to modules and interfaces