This presentation covers software and software engineering, an introduction to software development, modeling, analyzing simple requirements, and introduction to the CASE tool.

1. Arab Open University
2nd
Semester, 2006-2007
M301
Unit 4.1
Approaches to Software
Development
rattas@arabou.org.sa

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Topic Road Map
 Software and software engineering
An introduction to software development
Modeling
Analyzing simple requirements
Introduction to the CASE tool

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System
An assembly of components that are
connected together in an organized way.
Examples:
 Telephone.
 Human body.
 Super market software system.

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Software Characteristics
Malleability: easy to change.
Complexity.
Size.
 The number of errors in a system increases
with complexity and size.

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Software System Characteristics
Useful: meets user’s requirements.
Usable: easy to use.
Reliable: does not contain errors.
Flexible: easy to change.
Available: in its target environment.
Affordable: on time and within budget.

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Maintainability
Software system must be maintainable 
written and documented in such a way
that changes can readily be made.
 Important to minimize changing costs.

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Legacy systems
 Particular software system continues to meet its users’
needs.
 There may be little or no motivation to change or replace
it.
 Characteristics:
 Large.
 Critical to the system.
 Have probably been changed a number of times since their
inception.
 Difficult to understand.
 difficult to maintain.

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Divide and rule
Decompose a problem into smaller and
smaller parts or chunks until each one can
be comprehended or dealt with by an
individual.
Example:
 Hospital system = patient system + physician
system + pharmacy system.

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Divide and rule
 Partition  Projection

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Divide and rule
Coupling: the degree of interdependence
among the different components of a
system.
Low coupling is better because:
 Changes to one component are less likely to
propagate through the rest of the system.
 Components are easy to replace and reuse.

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Architecture
Describes the overall shape of the actual
or proposed software system.

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Topic Road Map
Software and software engineering
 An introduction to software
development
Modeling
Analyzing simple requirements
Introduction to the CASE tool

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Software Engineering
The establishment and use of sound
engineering principles in order to obtain
economically software that is reliable and
works efficiently on real machines.

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Software Development Activities
1. Analysis: includes requirements elicitation
where you identify the problem and
requirements specification where you decide
what needs to be done to solve the problem.
2. Design: how you will solve the problem.
3. Implementation.
4. Testing.

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Software Development Activities
5. Integration.
6. Maintenance.
7. Quality Management.
8. Project Management.

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Waterfall Model

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Iterative (Spiral) Development

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Incremental Development

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Topic Road Map
Software and software engineering
An introduction to software development
 Modeling
Analyzing simple requirements
Introduction to the CASE tool

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Modeling
A way of thinking about things and ideas
in the ‘real world’.
Example:
 Map.

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Modeling Language Rules
Syntax: determines what diagrams and
symbols exist.
Semantics: determines what the diagrams
and symbols mean.

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UML
Unified Modeling Language used to
develop object-oriented software systems.

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Types of Models
Static Models: describe the objects in a
software system and their relationships to
other objects.
Dynamic Models: describe the behavior of
a software system over time.

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Views in the UML

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Topic Road Map
Software and software engineering
An introduction to software development
Modeling
 Analyzing simple requirements
Introduction to the CASE tool

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Problem

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Tasks
1. Make reservation.
2. Check in.
3. Check out.

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Use Case View  who does what

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Main Elements
Actors.
Use Cases.
Relationships.

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Static View  noun identification

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Main Elements
Classes.
Associations.

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Dynamic View
 Activity view: shows both sequential and
concurrent groups of activities of a specific task.
 Interaction view: concerned with the exchange of
messages between the objects in a software
system.
 State machine view: record the different
possibilities that might arise for all instances of a
particular class.

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Activity View  Check in

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Main Elements
Activities.
Transitions.
Decision points.
Start and end points.

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Interaction View  Checking Jill into
the Ritz Hotel

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Main Elements
Objects.
Messages.
Object’s life line.
Object is active.

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State Machine View  Room Object

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Main Elements
State.
Transition.

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Topic Road Map
Software and software engineering
An introduction to software development
Modeling
Analyzing simple requirements
 Introduction to the CASE tool

40. Demo

41. TMA4 – Q1

42. Thank You!