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

Chapter 3. Architectural Patterns 55Peer 4Peer 1Peer 3Peer 2Figure 3.20: Example usage of Peer–to–Peer patternto lower components are forwarded by connecting layers and componentsdo not care which exactly sub–agent will execute it. Connectors must knowcomponents in order to return result of asynchronous operations.17. Active RepositoryOverview– this pattern is a variation of Shared Repository that providesa notification mechanism to Repository. Client elements do not have toinvoke Repository to check if there is something meant for them. Instead,Repository can notify all registered ClientsElementsRepository – is a core element of the pattern. It is meant to store, maintaindata and provide it to clients.Client – uses repository to store data in it and to obtain data from it.Relationships – all the client elements are aware of the repository andcan perform operations on it. Since Repository can notify Clients, all theconnections between Clients and Repository are bidirectional18. Remote Procedure CallOverview – The pattern assumes that all the remote procedures shouldbe treated, as they were local. User should not know that a procedure is executedsomewhere in the network. The procedures are mainly provider–dependentand can change over the years, therefore the description of the elements andrelationships bellow refer to just an example implementation of the patternElementsClient– is a frontend of the application. This element allows user to perform