Essay --

2. Critical Literature Review We relate the methods with respect to the criteria. The plan of the suggested approach is replacement, wrapping and migration. 2.1Replacements of Legacy Systems Replacement is not one of the policies. It may make sense to complete reshape of the legacy system from scratch. Reshaping the application from scratch is costly risky and time consuming, but has a good thing that it fulfills the organizations demands by giving a solution according to need and demand. Replacement can take place either by a strategy or incrementally. If the legacy system has defined structures then replace it incrementally. 2.2Wrapping Strategies The wrapping is another approach used for the implementation of SOA from legacy code. The useful legacy code is sticked with code wrapper to be integrated into an SOA system if the legacy system has a high business value and good quality code, wrapping can be a good option. The problematic thing in this approach is that it does not change the fundamental features of the legacy applications that are being integrated. Wrapping will not solve problems already present, such as problems in maintenance and Upgrading. In many cases, studying the internals of the legacy system is important and white-box modernization tools are required. 2.3Overview of wrapping techniques Sneed [11, 12] proposed a tool supported method for maintaining legacy code within an SOA environment. Legacy code Segments that accomplish a desired service or data reform are identified using Clustering tools and a new component is built by them. The new component is set a WSDL interface, and a SOAP framework is used. The technique has been demonstrated by wrapping a COBOL calendar function extracted from the legacy ... ...antage is that it is time consuming skilled resources are necessary for this and source code is required. There is still no general migration technique that can be applied that solves all of the problems that a developer may face. The required goal can be achieved by combining two or more modernization strategies according to the advantages and disadvantages of every strategy in the context. The reuse of legacy system components and their exposition as services are not always easy. In certain situations their exposition, as services will have an increased risk and a greater cost than their replacement completely with a new SOA architecture. The problem of modernization of legacy system has no perfect solution. Choosing a strategy is based completely on the objectives of the SOA architecture the budget and resources available and required time to achieve the project.