Software Engineering

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Software Engineering

• Requirements Analysis - OO
• Lecture 5

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Text

• This lecture covers material from Chapter 4
• However, I assume that you are comfortable with
  OO concepts!
• A problem I dont have last years projects that
  used an OO approach
• we are stuck with poor examples.

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OO/Structured differences

• Fichman Kemerer Process oriented methodologies
  focus attention away from the inherent properties
  of objects during the modeling process
• encapsulation
• classification of objects
• inheritance
• In SA - data is considered separately from
  processes which transform it -- top down
  development, and end to end processing sequences

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Several OO approaches

• Booch method -- Behavior/operational emphasis --
  identify classes objects, understand their
  behavior relationships, and refine
• Rumbaugh method -- Object Modeling Technique
  (OMT) -- 3 models
• object model objects, classes, their
  relationships and hierarchies

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OO approaches

• Rumbaugh
• dynamic model object system behavior, with a
  data emphasis
• functional model similar to DFD
• Jacobson method -- Object Oriented Software
  Engineering (OOSE) -- emphasis on use cases
• requirements
• analysis model

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OO approaches

• Coad Yourdon
• Identify Objects
• Define a generalization/specification structure
• Define a whole/part structure
• Identify subjects
• Define attributes
• Define services
• UML

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UML Views

• User model view
• Structural model view
• Behavioral model view
• Implementation model view
• Environment model view

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Domain analysis

• Creating a library of reusable classes/components

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Components of OO analysis

• Static view of classes
• Static view of attributes
• Static view of relationships
• Static view of behaviors
• Dynamic view of communication
• Dynamic view of control and time

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Steps of OOA

• Step I Use cases
• Step II CRC cards
• class types
• characteristics
• Step III Defining Structures hierarchies
  packages

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Steps of OOA

• Step IV Object-relationship model
• connect classes that are related (CRC cards help)
• use verbs to connect classes
• somewhat similar to ERD
• do not use modality

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Steps of OOA

• Step V Object-Behavior model
• use use-cases to identify events
• identify the events that drive the interaction
  sequence and to understand how they relate to
  objects

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Steps of OOA

• Step V Object-Behavior model
• create an event trace for each use case
• create an event-flow diagram for the system

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Event Trace
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Event Flow Diagram
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Steps of OOA

• Step V Object-Behavior model
• Build a state transition diagram (like the
  structured approach)
• review

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