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Migration of a Chosen Architectural Pattern to Service Oriented ...

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Chapter 2. Related Work 274. Media<strong>to</strong>r –mediates between Resource Layer and Entity Layer. The purpose<strong>of</strong> the layer is <strong>to</strong> manage business transactions, enforce business rules,instantiate business objects in Entity Layer and manage the memory cache<strong>of</strong> the application.Depends on: Resource Layer, Entity Layer5. Entity –represents all the business objects within the application.Depends on: Independent6. Resources –mediates between application and data sources. The source canbe a database, service or other external entity containing required information.Depends on: External ResourcesThe pattern fits well <strong>to</strong> for business solution and as the business solutions becomea subject <strong>of</strong> integration. The integration presented by L. Maciaszek aims atintegration with <strong>Service</strong> <strong>Oriented</strong> Architecture. The pattern is modernised inorder make the integration possible. The modernisation <strong>of</strong> the pattern is namedPCBMER–U (Utility) and introduces three new elements in<strong>to</strong> the pattern(seefigure 2.3).1. Broker –is a message broker2. Orchestration –encapsulates and executes a new business logic (see 4.3.2 formore information)3. <strong>Service</strong> Registry –is responsible for service discovering and depends only onmedia<strong>to</strong>r.The modification seems <strong>to</strong> have some contradiction. The first is that according<strong>to</strong> description, Registry depends on “utility’s business logic in Media<strong>to</strong>r” [52]what in fact is quite interesting because Media<strong>to</strong>r Layer does not depend onController Layer, consequently Media<strong>to</strong>r layer is not ”aware” <strong>of</strong> Controller layer.Registry may not discover higher level services located in Controller. The nextpotential contradiction is where Orchestration is introduced. According <strong>to</strong> figure3 in [52] Controller depends on Orchestration what seems <strong>to</strong> be against role<strong>of</strong> Orchestration, because in fact Orchestration / Process <strong>Service</strong>s depend onunderlying services what in this case may mean that Orchestration depends onservices allocated in Controller layer. The last contradiction refers <strong>to</strong> the figure 3and the description. Description says that Broker and Orchestration depend onlogic in Controller Layer while the dependency in the picture is opposite. Thesame situation refers <strong>to</strong> Media<strong>to</strong>r Layer and Registry.

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