Modeling Systems Requirements: Events and Things

Overview

Document functional requirements by creating models 

Models created during analysis phase activity: Define system requirements

Two concepts define system requirements in traditional approach and object-oriented approach

·         Events

·         Things

 Models and Modeling

·         Analyst describes information system requirements using a collection of models

·         Complex systems require more than one type of model

·         Models represent some aspect of the system being built

·         Process of creating model helps analyst clarify and refine design

·         Models assist communication with system users

 Reasons for Modeling

      1.      learning from the modeling process

2.      reducing complexity by abstraction

3.      remembering all of the details

4.      communicating with other development teams members

5.      communicating with a variety of stakeholders

6.      documenting what was done for future maintenance/enhancement

 Types of Models

Different types of models are used in information systems development

1.      Mathematical - formulas that describe technical aspects of the system

2.      Descriptive - narrative memos, reports, or lists that describe aspects of the system

3.      Graphical - diagrams and schematic representations of some aspect of the system

 Overview of Models Used in Analysis and Design

·         Analysis phase activity named “define system requirements”

·         Logical models

·         Provide detail without regard to specific technology

·         Design phase

·         Physical models

·         Provide technical details

·         Extend logical models

 Models Used in Analysis

·         Events list

·         Data flow diagram (DFD)

·         Entity-relationship diagram (ERD)

·         Data-flow definition

·         Data element definition

·         Process description/structured English/action diagram

·         Location diagram

·         Class diagram

·         Use case diagram

·         Sequence diagram

·         Collaboration diagram

·         Statechart diagram

 Models Used in Design

·         Screen layout

·         Report layout

·         System flowchart

·         Structure chart

·         Database schema

·         Network diagram

·         Deployment diagram