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

Chapter 2. Related Work 23between all the provided data. In order to allocate services, architects have toset cutting points manually and divide the diagram into sub–trees. The sub–treebecome services. During service selection, architects have to take into considerationother information retrieved during previous steps as well as the amount ofdependencies in order to receive coarse grained and loosely coupled services (see4.3.1).Service Packaging and Integration This is the last step of presented Gray–Boxtechnique. The step accomplishes the process of migration from legacy system towardsService–Oriented Architecture. The last step is composed from a sequenceof three sub–steps [84]:1. Refinement –the services obtained as a result of all the previous steps areloosely coupled, but they still contain some dependencies. Refinement increasesindependence of those services and improve their quality by removalof all the “dead” code and unrelated interactions of interfaces. During thisprocess also an interface for service communication is established [84].2. Component integration and packaging –component integration takes previouslyrefined services and connects them with a “glue code” that serves asan adapter in order to transform ingoing and outgoing invocation. Additionally,some differences between domain and retrieved model may appear.The differences should be filled up with new services.3. Interface design –this step is meant to create interfaces[84],but in fact theoutput is a contract that specifies exact input and output for each operationof the service. Also an interface –a representation of the contract–is created.Application of clustering seems to be very promising solution because it base onvery basic human activity–classification [4]. Generally, clustering is meant to reorganizegroups of entities by taking into consideration their similarity and basedon that divide them into more homogenous groups[4]. The similarity can vary asa domain of analysis and can be understood as for instance similarity of propertieswhich is measured with metrics. Method applied in this approach bases onan improved agglomerative hierarchical clustering [4],This technique emphasizesfunctional aspects [4]that are essential in SOA. The technique is presented as aset of processes and an algorithm.2.1.5 Advantages and drawback of Taxonomy AnalysisTaxonomy Analysis analyses code of the migrated application in order to identifyservices and relationships between them.