Software Design 2e - DIM

Table 7.1The selection of black box design representations129Representation formData-Flow DiagramEntity–Relationship DiagramState Transition DiagramStatechartStructure Diagram (Jackson)ViewpointsFunctionalData modellingBehaviouralBehaviouralFunctional, datamodelling, behaviouralDesign characteristicsInformation flow, dependency of operations onother operations, relation with data storesStatic relationships between design entitiesState-machine model of an entitySystem-wide state model, including parallelism(orthogonality), hierarchy and abstractionForm of sequencing adopted (operations, data,actions)Black box notationsUML: Class DiagramConstructionalInteractions between classes and objectsUML: Use Case DiagramBehavioural andfunctionalInteractions between a system and other ‘actors’UML: Activity DiagramBehavioural andfunctionalSynchronization and coordination of systemactivitiesTable 7.2The selection of white box design representationsRepresentation formStructure ChartClass and Object DiagramsSequence DiagramsPseudocodeViewpointsFunctional andconstructionalConstructionalBehaviouralFunctionalDesign characteristicsInvocation hierarchy between subprograms,decomposition into subprogram unitsUses relationships between elements, interfacesand dependenciesMessage-passing sequences, interaction protocolsAlgorithm formA final point that follows on the one that was made in the previous paragraph: thelevel of detail provided in the descriptions of the following sections is not intended tobe consistent. In particular, those notations that will be used in the later chapterson design methods are not normally described in such complete detail as others, sincefurther examples of their use will be provided in the relevant chapters.7.2 Black box notationsTo remind ourselves of the discussion in Chapter 2: a black box notation is one that isconcerned with the external properties of the elements of a design model. That is, it isused to describe what an element will do, rather than how it is to do it. We can alsoconsider such forms as performing the role of ‘external memory devices’, used to helpincrease the limited capacity of human working memory (Vessey and Conger, 1994).Our choice of forms is a mixed one, in terms both of historical and technologicalfactors. We begin with the Data-Flow Diagram (DFD), a form which is generally