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

Chapter 5. Guidelines 112Solution The pattern introduces a state repository that is meant to maintainstate of stateful services. Stateful services delegate their state to specialservices in order to free system resources. The state is not transferred automatically.The transfer occurs when special criteria are met. The criteriacan be for instance an extending waiting for a response. This solution occursto be very useful when an asynchronous communication is applied.Result Context State of stateful services can be stored when specialcriteria are met. Afterwards, when it is needed the state can be restored.12. Name UI MediatorProblem Business services bind into process many independent services.The execution time of those services may vary and it can take a while toprovide result requested by the user.ContextAn application is interacting with users.Forces(a) Services creating the process can be dynamically changed.(b) Time needed for execution of an operation varies and depends on loadand geographical location of a service.Solution Application of the pattern introduces an additional layer thatprocesses information about progress of invoked operation. The informationis further acquired by frontends and presented to users.Result Context An application that is able to provide continuously feedbackabout progress of invoked operation.5.2 GuidelinesThe guidelines for migrated system should use existing code and documentation.Application of Top– Down approach bases more on available documentation becausea good understanding of business domain and associated business processesis needed to divide the whole application into smaller parts. Each guideline introduceda SOA architectural pattern in order described by SOA pattern language(see section sec:SOApatternLanguage). Application of a subsequent guideline removessome code from migrated system and migrates it to the target system.