Software Engineering

1
Software Engineering

• Requirements Analysis - Structured
• Lecture 4

2
Five major areas

• Problem Recognition
• Evaluation and Synthesis
• Modeling
• Specification
• Review

3
Specification - Principles

• Separate functionality from implementation
• Include system response to various external
  stimuli
• Discuss underlying interactions with OS and other
  S/W
• Design spec so its easy to change
• Be consistent with diagrams and notation

4
Specification - Tools

• Rational Rose
• Visible Analyst -- www.visible.com/train/demoforms
  /edform_forms.htm

5
Review

• First among developers
• Then with customers and developers
• Customers and developers sign off -- creating a
  contract
• Problems
• difficult to test spec
• difficult to determine impact of changes that are
  suggested in the review

6
Structured Analysis

• Objectives
• describe what is required
• establish a basis for design
• define a set of requirements (that may be
  validated after s/w is built)

7
Elements
8
Step I

• Building the Use Cases
• Understanding the Use Cases

9
Step II - Data Modeling

• What are the data objects (composite
  information)?
• What attributes does each data object have?
• What are the relationships that connect it to
  other data objects?
• Cardinality
• Modality

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Data Modeling

• No references to operations that act on the data
  -- c.f. OO
• Building the ERD

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Sample ERD
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Step III - Functional Modeling

• Input, processing, output
• Refine to give more detail
• No explicit sequencing of processing

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Step IV - Behavior Modeling

• State transition diagrams
• system states
• what causes transformations between states
• state an observable mode of behavior

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Sample STD
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Data Dictionary

• Often implemented with CASE tools
• Contains the name of each data item
• Where used/how used
• Content description
• Other info restrictions, limitations, preset
  values, etc.