Software Design 2e - DIM

117‘Thin’ clientBrowserNetworkServerApplicationsoftwareThe architecture conceptDatabaseFigure 6.4The data-centred repository style: simple client–server system.Table 6.4FeatureThe data-centred repository architectural styleInstantiation in data-centred repositoriesComponentsConnectorsControl of executionData communicationControl/data interactionDesign reasoningStorage mechanisms and processing units.Transactions, queries, direct access (blackboard).Operations are usually asynchronous and may also occur in parallel.Data is usually passed via some form of parameter mechanism.Varies quite widely. For a database or a client–server system, these may behighly synchronized, whereas in the case of a blackboard there may be littleor no interaction.A data modelling viewpoint is obviously relevant for database andclient–server systems. The wider variation of detail that occurs in this styletends to preclude the widespread use of more procedural design approaches.later chapters on design practices. However, the above three offer good examples thatillustrate the basic concepts.6.2.4 The role of the architectural concept in knowledge transferAt this stage, the obvious question is: ‘what role do these ideas perform in terms ofthe task of designing software?’ A number of answers to this question were suggestedby Garlan and Perry (1995) and were reviewed in Section 6.2.1. Taking a slightly narrowerfocus, in terms of the issues that are more directly the concern of this book, wecan identify the following key roles.