LlosengCh05E2

LlosengCh05E2 - Object-Oriented Software Engineering...

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Unformatted text preview: Object-Oriented Software Engineering Practical Software Development using UML and Java Chapter 5: Modelling with Classes 1 2 5.1 What is UML? The Unified Modelling Language is a standard graphical language for modelling object oriented software At the end of the 1980s and the beginning of 1990s, the first object- oriented development processes appeared The proliferation of methods and notations tended to cause considerable confusion Two important methodologists James Rumbaugh and Grady Booch decided to merge their approaches in 1994. They worked together at the Rational Software Corporation In 1995, another methodologist, Ivar Jacobson, joined the team His work focused on use cases In 1997 the Object Management Group (OMG) started the process of UML standardization 3 UML diagrams Class diagrams describe classes and their relationships Interaction diagrams show the behavior 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 4 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 5 What constitutes a good model? A model should use a standard notation be understandable by all stakeholders help software engineers to develop 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 6 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 7 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 - means private, + means public 8 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 9 Labelling associations Each association can be labelled, to make explicit the nature of the association 10 Analyzing and validating associations Many-to-one A company has many employees, An employee can only work for one company....
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LlosengCh05E2 - Object-Oriented Software Engineering...

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