lecture5_2up

lecture5_2up - Object-Oriented Software Engineering...

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Object-Oriented Software Engineering Practical Software Development using UML and Java Chapter 5: Modelling with Classes Lecture 5 226 5.1 What is UML? The Unifed Modelling Language is a standard graphical language For modelling object oriented soFtware • At the end of the 1980s and the beginning of 1990s, the Frst object- oriented development processes appeared • The proliferation of methods and notations tended to cause considerable confusion • Two important methodologists Rumbaugh and Booch decided to merge their approaches in 1994. —They worked together at the Rational Software Corporation • In 1995, another methodologist, Jacobson, joined the team —His work focused on use cases • In 1997 the Object Management Group (OMG) started the process of UML standardization
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227 UML diagrams • Class diagrams —describe classes and their relationships • Interaction diagrams —show the behaviour of systems in terms of how objects interact with each other • State diagrams and activity diagrams —show how systems behave internally • Component and deployment diagrams —show how the various components of systems are arranged logically and physically 228 UML features • It has detailed semantics • It has extension mechanisms • It has an associated textual language Object Constraint Language (OCL) The objective of UML is to assist in software development —It is not a methodology
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229 What constitutes a good model? A model should • use a standard notation • be understandable by clients and users • lead software engineers to have insights about the system • provide abstraction Models are used: • to help create designs • to permit analysis and review of those designs. • as the core documentation describing the system . 230 5.2 Essentials of UML Class Diagrams The main symbols shown on class diagrams are: Classes - represent the types of data themselves Associations - represent linkages between instances of classes Attributes - are simple data found in classes and their instances Operations - represent the functions performed by the classes and their instances Generalizations - group classes into inheritance hierarchies
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231 Classes A class is simply represented as a box with the name of the class inside • The diagram may also show the attributes and operations • The complete signature of an operation is: operationName(parameterName: parameterType …): returnType 232 5.3 Associations and Multiplicity An association is used to show how two classes are related to each other • Symbols indicating multiplicity are shown at each end of the association
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233 Labelling associations • Each association can be labelled, to make explicit the nature of the association 234 Analyzing and validating associations Many-to-one —A company has many employees, —An employee can only work for one company. - This company will not store data about the moonlighting activities
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lecture5_2up - Object-Oriented Software Engineering...

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