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Info 1409 Systems Analysis & Design Module

Lecture 8 – Modelling tools and techniques

HND Year 12008/9

De Montfort University

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Objectives

The objectives of this lecture are to explain

CASE tools Unified modelling language Use Case diagrams

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Lecture objectives

By the end of this lecture you will: Understand the need for specialist tools

and methods in systems modelling Have been introduced to Unified

Modelling language and its concepts Understand the need for Use Case

models.

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Introduction to system modelling

Producing the logical view of a system means:

producing graphical models which use non technical language for descriptions.

Representing the system at various stages of development

Charting business processes and requirements and interactions.

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CASE tools

Computer Aided Software Engineering

CASE helps developers design and construct information systems

This module will introduce you to a CASE tool in your Lab sessions in term 2

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The CASE environment

Using a CASE tool can: Speed up the development process Plan ‘business driven’ systems Support the software development

process Produce models and comprehensive

documentationGiving an industry standard for all the

above tasks.

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Definition of CASE tools

As early as the 1960’s programmers used tools such as editors and code debuggers to write programs.

Today we live in a ‘software driven’ world. CASE tools are now powerful resources that systems analysts need in order to build complex information systems.

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Definition of a CASE environment by Carnegie Mellon

From Shelley et al

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CASE terms and concepts

A typical CASE tool is a set of individual software tools that share information in what is called a ‘Repository’

CASE tools can be used to model, document, engineer and construct the information system

They are software tools which can provide the following functions:

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Individual tools

1. Documentation tool

The CASE environment builds up a database of information about the system model and can then produce the necessary documentation.

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Individual tools (2)

2. Engineering tools These translate business processes into

applications, by producing models like Use Case or Data flow diagrams

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Individual tools (3)

3. Construction tools-This facility generates code, screen layouts

and reports in languages such as Java, C++ and VB)

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FourGen offers a screen generator that can create Data entry screens, and forms, program code and reports

Illustration by permission from Shelley et al

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Future TrendsQuote from Shelley Cashman et al (p551)

“Traditional CASE software evolved from functional tools (such as code editors) to help developers envision and construct an entire information system”

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Future TrendsQuote from Shelley Cashman et al (p551)

“ It is predicted that the next generation of CASE tools will go even further, working with internal and external business processes for organisations”.

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Unified Modelling language

What is Unified modelling language….?

Before proceeding, we really need to know.

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Activity time

To answer this question we are going to discuss and brainstorm.

You need to group in 3’s for this one

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Some facts to help you

UML is just a syntax. It says nothing about how too create a model

UML is well documented but little understood It was developed by Grady Booch, Jim

Rumbaugh and Ivar Jacobon at Rational Software

UML specifies 8 different diagrams. Not all are used in practice.

A use case diagram shows the functionality of the system from the ‘outside in’

Class diagrams show the static structure of the systems

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Activity time (Brainstorming)

Think about and talk about how you might answer the following question:

What IS Unified Modelling Language and what is if for?

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Unified modelling language is..

Give your definitions here:

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UML Benefits

UML : Uses Object Oriented design

concepts Is a popular method of visualising

and documenting software systems. Is independent of any specific

programming language

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Benefits of Unified Modelling language

UML : Provides graphical tools for

example Use Case models Can represent the info system

from Users standpoint.

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Use Case Diagrams During requirements modelling analysts

and users together model the system functions

A Use Case diagram visually represents the interaction between Users and the Information system

Use Case diagrams can be drawn freehand, or using Case tools.

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In this diagram the Actor is a customer and the Use Case is a credit validation performed by the system.

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Use Case components cont.. The Use Case is the function that the

Actor (user of the system) wants the system to perform

It is represented by an ellipse with a written description of what the function needs to be.

The line joining the Actor and the Use Case is called an association

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Use Case components cont.. The Actor is represented by a human

figure (usually a stick person)

There is a system boundary which is illustrated by the square box in which the activities of the system take place.

Please note that the Actor is external to the system – (at the system interface).

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Use Case documentation It is always necessary to document diagrams

in the modelling process.

The reason is that analysts and designers work as a team (with Users and with each other).

A model alone can be subject to interpretation.

A descriptive table to accompany a diagram ensures clarity

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This table documents the Credit card validation in the previous example

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Use Case functions

The successful completion part of the table outlines the activities that make up the functions of the Use Case.

In this case there are 3 Notice that the three activities consist of

an input a process and an output

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Activity time

Draw the Use Case example in slide 24. Label its component parts and note down where the inputs/outputs and processes would occur.

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In conclusion

At the end of this lecture you have: Been introduced to UML Learned about the use of CASE tools Been introduced to modelling

techniques Seen examples of Use Case models Recognised the need for

documentation

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Background reading

Chapter 3 – Modelling tools and techniques Pp98-100Part 5 of the Systems Analysis Toolkit

fromSystems Analysis & Design. Shelley Cashman and Rosenblatt 6th/7th EditionThomson Course Technology 2006/7