CSC/ECE 517 Fall 2007/wiki2 4 2q
A Guide to Use Cases on the WEB
Topic :Use cases. There are even more pages on the Web on use cases than on MVC. If someone wants to learn about them, what should (s)he do? Look at the first few hits in Google? I expect we can do better than that. Write a review of the use-case sites on the Web. Which are best for learning about the concept? Which have the most instructive examples? Which teach advanced concepts that are not apparent in perusing most use-case sites? Read at least several dozen pages before deciding how to organize your overview.
Introduction
This page outlines a review of the use-case sites on the Web which can be useful to best understand the concept. Also a few instructive examples are covered paying attention to the basic use case as well as advanced concepts that are not apparent in perusing most use-case sites.
What is a Use Case?
Definition
A use case is a methodology used in software and systems engineering to understand and identify the functional requirements of a system. Use cases describe the interaction between a primary actor, the initiator of the interaction and the system itself, represented as a sequence of simple steps[1][2].
An actor who can more generally be described as the user of the system, is the external entity and can be a person or another system itself. A use case can be best described as what happens when the actor is using the system to achieve some goal. This goal is nothing but the end result which follows the sequence of events as described in the use cases.
Every use case gives a complete list of events which occur from the time the actor starts interacting with the system till the time the final goal is achieved.A use case also records all the possible scenarios that may occur while trying to reach the desired goal. We can think of it as existence of a main course of events that will occur in normal circumstances, to which the exceptional cases are added. Anything that is not relevant to the actor/user is not a part of the use case.
Listed below are a few links to external websites which further illustrate this concept.
Examples using Use Cases
How to write a typical Use case
UML Diagrams and Use cases
"The Use case diagram is used to identify the primary elements and processes that form the system. The primary elements are termed as "actors" and the processes are called "use cases." The Use case diagram shows which actors interact with each use case."[3]
They are useful in providing a pictorial view of the interactions between the users(actors) and sets of events(use cases) associated with the system.They also eveolve as the projects or system change with time. The standard elements of a use case diagram makes comprehension easy for anyone trying to understand the use case.
Listed below are useful links in understanding how to draw typical use case diagrams.
Self Service Machine
This example provides the typical Use Cases in a self service machine. Some of the aspets of using a self service machine are: buying a product, re-stocking the machine, collecting the money etc. The following link expands on how to do this and also provides the UML diagrams which depict the interaction between the users and system through the use case
Club Information System
This example provides one use case but disctinlty provides a step by step analysis of the events that constitute a Use Case. It mentions the actors, pre-conditions, Exceptions and Alternative scenarios.
Purchase order
This example provides a typical use case specification by listing the Activity, Result, Constraints and Extensions involved with a purchase order from a Finance web page.
ATM system
This example is a little more involved in that it provides a number of use cases associated with using an ATM system including cash withdrawal, transfers, deposits, balance enquiry, etc.
A shopping website order Process
This is a very good example that describes the scenarios and extensions involved in writing a use case for a online shopping order. It also describes the UML diagram.
Other Useful Links on the web
Advanced Concepts on Use Cases
Links on the Web
References
- [1] Ivar Jacobson (1992). Object-Oriented Software Engineering. Addison Wesley Professional. ISBN 0-201-54435.
- [2] Wikipidea Page Basic definition of Use Case
- [3] Use Case Diagrams
External Links
Wikipidea Page Basic definition of Use Case