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

Chapter 5. Guidelines 108SolutionApplication of the pattern separates policies from services.Result Context The policies are separated from services. It is easier tokeep all the policies up to date. Update of policy affects all the servicesusing this policy in the same time.5. Name Utility AbstractionProblem Services, even those that do not provide redundant functionalitymay perform some common operation. Those operations are redundant.The redundancy requires additional effort for testing and maintenance.Context An application contains some common functionality that usedin code in several places.Forces(a) Common functionalities are used by code in several places(b) Those functionalities do not exist in requirements - they are ratherhelpers for architects and developers(c) Different vendors may not be aware that other vendors implementedthe same common functionalitySolution Utility Abstraction defines one layer containing common utilityservices. The layer contains mainly services without business concern,therefore in opposite to business-based services, utility services are developedmainly by architects and developers what raises problems related tocontent of such service. Teams need good communication in order to avoidredundant services.Result Context The application has clearly separated and implementedcommon functionalities that are further wrapped into services.6. Name Canonical ResourcesProblem Modern systems require access to external resources like databases,central directories or transaction management frameworks. The resourcesare accessed by many subsystems of the system. The access logic becomesa part of the subsystem.