DEV475 Mastering Object-Oriented Analysis and Design with UML ...
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DEV475 Mastering Object-Oriented Analysis and Design with UML ...

DEV475 Mastering Object-Oriented Analysis and Design with UML ... DEV475 Mastering Object-Oriented Analysis and Design with UML ...

crnarupa.singidunum.ac.rs
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12.07.2015 Views

DEV475 Mastering Object-Oriented Analysis and Design with UMLWhat Is an Entity Class?What Is an Entity Class?• Key abstractions of the systemAnalysis classstereotypeUse CaseBusiness-DomainModelArchitectural AnalysisAbstractionsGlossaryEnvironment IndependentMastering Object Oriented Analysis and Design with UMLCopyright © 2003 Rational Software, all rights reserved 18Entity objects represent the key concepts of the system being developed. Entityclasses provide another point of view from which to understand the system, becausethey show the logical data structure. Knowing the data structure can help youunderstand what the system is supposed to offer its users.Frequent sources of inspiration for entity classes are the:• Glossary (developed during requirements)• Business-Domain Model (developed during business modeling, if businessmodeling has been performed)• Use-case flow of events (developed during requirements)• Key abstractions (identified in Architectural Analysis)As mentioned earlier, sometimes there is a need to model information about an actorwithin the system. This is not the same as modeling the actor (actors are external. bydefinition). In this case, the information about the actor is modeled as an entityclass. These classes are sometimes called “surrogates.”6 - 18

Module 6 - Use-Case AnalysisThe Role of an Entity ClassThe Role of an Entity ClassActor 1Actor 2Store and manage information in the systemMastering Object Oriented Analysis and Design with UMLCopyright © 2003 Rational Software, all rights reserved 19Entity classes represent stores of information in the system. They are typically used torepresent the key concepts that the system manages. Entity objects (instances of entityclasses) are used to hold and update information about some phenomenon, such asan event, a person, or a real-life object. They are usually persistent, having attributesand relationships needed for a long period, sometimes for the lifetime of the system.The main responsibilities of entity classes are to store and manage information in thesystem.An entity object is usually not specific to one Use-Case Realization and sometimes itis not even specific to the system itself. The values of its attributes and relationshipsare often given by an actor. An entity object may also be needed to help performinternal system tasks. Entity objects can have behavior as complicated as that of otherobject stereotypes. However, unlike other objects, this behavior is strongly related tothe phenomenon the entity object represents. Entity objects are independent of theenvironment (the actors).6 - 19

<strong>DEV475</strong> <strong>Mastering</strong> <strong>Object</strong>-<strong>Oriented</strong> <strong>Analysis</strong> <strong>and</strong> <strong>Design</strong> <strong>with</strong> <strong>UML</strong>What Is an Entity Class?What Is an Entity Class?• Key abstractions of the system<strong>Analysis</strong> classstereotypeUse CaseBusiness-DomainModelArchitectural <strong>Analysis</strong>AbstractionsGlossaryEnvironment Independent<strong>Mastering</strong> <strong>Object</strong> <strong>Oriented</strong> <strong>Analysis</strong> <strong>and</strong> <strong>Design</strong> <strong>with</strong> <strong>UML</strong>Copyright © 2003 Rational Software, all rights reserved 18Entity objects represent the key concepts of the system being developed. Entityclasses provide another point of view from which to underst<strong>and</strong> the system, becausethey show the logical data structure. Knowing the data structure can help youunderst<strong>and</strong> what the system is supposed to offer its users.Frequent sources of inspiration for entity classes are the:• Glossary (developed during requirements)• Business-Domain Model (developed during business modeling, if businessmodeling has been performed)• Use-case flow of events (developed during requirements)• Key abstractions (identified in Architectural <strong>Analysis</strong>)As mentioned earlier, sometimes there is a need to model information about an actor<strong>with</strong>in the system. This is not the same as modeling the actor (actors are external. bydefinition). In this case, the information about the actor is modeled as an entityclass. These classes are sometimes called “surrogates.”6 - 18

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