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

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Chapter 3. <strong>Architectural</strong> <strong>Pattern</strong>s 45Pipe – forwards processed data <strong>to</strong> next filter.Relationships – Each pipe connects two filters and each filter has <strong>to</strong> beconnected <strong>to</strong> at least one pipe. There is no possibility <strong>to</strong> connect a pipe <strong>to</strong>a pipe or a filter <strong>to</strong> a filter directly. Additionally, pipes <strong>of</strong>fer only unidirectionalconnections (see figure 3.7)Filter 1PipeFilter 4PipeFilter 3PipeFilter 2PipeFigure 3.7: Example usage <strong>of</strong> Pipes and Filters pattern3. BlackboardOverview – the pattern is very useful when no deterministic solution isknown. The pattern improves solution-finding process that bases on smalldeterministic solutions.ElementsBlackboard – contains all currently gained knowledge or solutions. Theblackboard serves also as a place for future solutions / knowledgeKnowledge source – provides more advanced or more complete solutionbased on own data and blackboard’s information.Modera<strong>to</strong>r – moderates knowledge improvement. The element determinesthe order in which every source <strong>of</strong> knowledge has <strong>to</strong> access the blackboard.Relationships – Modera<strong>to</strong>r is in relationship with Knowledge Source andBlackboard. Knowledge Source can operate only on Blackboard. Blackboarddoes not invoke other elements <strong>of</strong> the pattern (see figure 3.8).

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