Structured Analysis and Design

1
Structured Analysis and Design

• Dr. Jo Hartley
• Room N404
• Analysis and Design Module

2
Syllabus

• Introduction to real-time systems and Essential
  model
• Data transformations and Data flows, Data stores,
  Conservation of Data and Synchronous Data rules
• Control transformations, Event and Control flows,
  and Event stores

• Organising the model
• State-transition diagrams and Data transformation
  specification
• Implementation model and Data dictionary
• Processor level, Task level and Module level

3
Lecture 7.Structured Analysis and Design

• Data transformation specifications
• When
• How
• Using Yourdon for Data transformation
  specifications

4
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

5
How do we specify

• May use
• Narrative text
• Flowcharts
• Functions in tabular/graphic form
• Decision tables/trees

6
Structured Ordinary Language

• Remove
• adjectives
• adverbs
• compound sentences
• asides
• footnotes

• Include
• inputs/outputs
• get (for input flows)
• issue (for output flows)
• selection
• if, then, else, end if
• iteration
• for each, do, end for
• while, do, end while
• repeat, until
• create, find, obtain, store, delete, calculate

7
Using Yourdon for Data transformation
specifications
Click on Data Transformation
Select child diagram PSPEC Open
Add Narrative text using inputs and outputs
8
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.

9
The Essential Model
10
The Implementation Model