System Analysis lecture 4

This week mainly covers the Analysis part
During the Analysis part there are few steps the Analyst should follow, the main thing is modelling

Reason for modeling
Learning from modeling process
Reducing complexity of abstaction
communicating with other members
documenting for future maintenence

Types of Models
Mathermatical
Descriptive
Graphical
Defining system requirments
Logical model - provide detail without regard to specific technology
Design phase
physical model
extend logical models

Events related to system requirments
Events occures at specific time and place
trigger - this means the system process

Requirment definition
This determines relevant events
common events are external events, temporal events and state events

Identifying events can be difficult to determine but these are very useful for trace a transaction's lifecycle.
Charactoristics of entities
1.Relationship
2.Attribute
Data entities
*Things system needs to store data about in traditional IS approach.
*This used to create the database design model for relational database

Objects

• Objects does the task and stores information within the system
• Objects also have behaviours and attributes

1.Class-type of thing

2.Object-Each specific thing

3.Methods-Behaviours of objects of the class

The class diagram

the main types are generalization- general superclass to specialized subclass

Aggregation-this relates to objects and its parts.

UML and its purposes

this presents object management

1.The purpose is promote theory and practice of object technology for developement of distributed systems

2.Provide common architectural framework.

The requirments of object oriented approach

• system requirments are specified and documented through process of building models
• Events are the new business processes that new system must perform
• Things are problem domain objects.

Object oriented models

• Class diagram
• usecase diagram
• system sequence diagrams
• state chart diagrams
• activity diagrams