ObjectOriented Analysis and Design

1
Object-Oriented Analysis and Design
2
Overview

• To frame our discussion, consider
• What principles can we employ in software
  development that contribute significantly to the
  production of quality, reliable, and maintainable
  software products?
• What empirical support is there to encourage
  their adoption?
• How and when do we employ these principles in
  constructing software?

3
Outline

• Strategies
• Analysis
• Design
• OO Analysis
• OO Design
• Development

4
Why Strategies?

• Support for the designer
• Aid in communication with users
• Support for maintenance staff

5
What Strategies?

• Abstraction
• Simplifying the description of real-world
  entities to its essentials
• Separation
• Treating the what and the how independently
• Composition
• Building a system as the assembly of parts
• Generalization
• Identifying commonalities among entities

6
Strategies and OO

• Abstraction
• Separation
• Composition
• Generalization

7
Analysis

• Analysis emphasizes an investigation of the
  problem and the context in which a solution must
  reside.

8
Analysis Model (1)

• Three objectives of the analysis model
• 1. describe what the customer requires,
• 2. establish as basis for the creation of a
  software design,
• and
• 3. define a set of requirements that can be
  validated.

9
Analysis Principles (1)

• 1. Examine and Understand the Problem Domain
• Information Content
• The individual data and control objects that make
  up the available inputs to the system.
• Information Flow
• The way data and control are changed as each
  moves through the system.
• Information Structure
• Defines the internal representation of the items
  and how information items relate to one another.

10
Analysis Principles (2)

• 2. Define the functions the software must perform
  (requirements).
• Construct a model that provides an increasing
  level of detail regarding the functions the
  software must provide.

11
Analysis Principles (3)

• 3. Represent the behavior of the software.
• A behavioral model represents the states of the
  software and the events that cause software to
  change state.

12
Design

• Providing a model from which an implementation
  can be derived.

13
Design Principles

• 1. Design process should not suffer from
  tunnel vision.
• 2. Design should provide traceability to the
  analysis model.
• 3. Design should not reinvent the wheel.
• 4. Design should be consistent with problem
  domain.
• 5. Design should exhibit uniformity
  integration.
• 6. Design should facilitate change.
• 7. Design should accommodate the unexpected.
• 8. Design is not coding!!!
• 9. Designs have qualities too!
• 10. Designs should be reviewed!

14
OO Analysis

• Emphasizes finding and describing the objects in
  the problem domain.

15
OO Design

• Defines the logical software objects that will be
  implemented. Software objects have attributes
  and methods.

16
Development

• Plan and Elaborate
• Plane, Define Requirements, prototype
• Build
• Construct
• Deploy
• Make the system operational

17
Iterative Development

• Based on successive enlargement and refinement of
  a system. Each iteration of the process is a
  complete development cycle of analysis, design,
  implement and test.

18
Use Cases

• Narrative Descriptions of domain processes
  (activities).
• These are a preliminary step in gathering
  requirements for a system.
• Iterative development can be organized by use
  case requirements..

19
OO Analysis

• Define essential use cases
• Refine Use case diagrams
• Refine Conceptual Model
• Refine Glossary
• Define System Sequence Diagrams
• Define Contracts
• Define State Diagrams

20
Conceptual Modeling

• A conceptual model is a representation of
  concepts or objects in the problem domain.
• Conceptual models should be developed
  incrementally. Thus avoiding increasing the
  level of detail too soon.