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

Chapter 5. Guidelines 114standard. The communication can be conducted for instance over RPC orHTTP with SOAP as a message standard. A pair of HTTP and SOAPmessages is widely used in Web Services [32] but it is one of the biggest obstaclesduring Web Service adaptation [59].However reliable message specificationand SOAP reliability headers increase messaging reliability, it stilldoes not guarantee message delivery, message status notification, duplicateelimination and message ordering [59].Therefore SOAP over HTTP shouldbe avoided in mission critical system. Instead protocols like WebShare MQ,Java Messaging Service (JMS), RosettaNet or Electronic Data Interchange(EDI) should be applied [59].ViewViewController+ Cannonical Protocol =ControllerModelModelFigure 5.2: Migration step 23. Unify used schemasApplied SOA pattern: Canonical SchemaHow to: At this point only a schema document is needed. The documentwill be filed up with definitions when new services will be identified andimplemented. The definitions present in schema are further used by otherservices. One important thing is that while next types of information aredefined, they should base on types that are currently defined. In otherwords, it is highly recommended to reuse exiting definition of informationand it does not generate additional dependencies because Schema describesinformation types in XML. Reuse of existing definitions helps to avoid redundantdefinitions and standardises domain vocabulary across the company.Finally, schema should be divided into many smaller documents thatdescribe a set of related information. The documents should be broken intonamespaces. A naming conversion should be also established. See figure5.3 for general idea.4. Unify policiesApplied SOA pattern: Policy Centralisation