In today’s computing world, services are slowly emerging and are made available as quickly as possible. However, this is not an easy task since a large amount of information needs to define the functionality of the system. To alleviate this problem, Service-Oriented Computing helps solve this through the decomposition of monolithic legacy systems into a loosely coupled one which is wrapped by various service adapters. Service Oriented Computing, commonly known as SOC, enables developers to design software systems as a set of services and allows them to recursively construct software systems.
It enables them to design loosely coupled software components which can then be integrated with other software systems. This software paradigm is based on the idea that web services define the technologies upon the implementation of such paradigm. The web services allow software integration by exploiting the infrastructure of the World Wide Web which offers an opportunity to continue using business functions which are provided by the legacy systems.
One of the important aspects to be addressed in mitigating a legacy system includes the transformation of the interacting paradigm in order to obtain the execution of legacy system functionality into the request/response paradigm. This request/response paradigm is a typical paradigm of Web Services. In the same manner, web service is based on request/response model, in which a client invokes a service which is implemented by a provider party. Hence, to make a legacy system accessible as a web service, the interface must be changed and must adapt the interaction paradigm of the web service.
This kind of transformation can be made possible through white box modernization techniques which require the code to be modified or by black box which do not require any code change at all. Critique The concept of legacy system mitigation is a straightforward approach. There are certain characteristics, though, which may complicate the task. To approach this, certain strategies may be applied such as providing a roadmap, platform/tool/vendor independent, scales to different domains, process/service integration, content integration, Web 2. enablement, mashup enablement and quality of service.
To solve problems relating to legacy systems, the approach used is the black box modernization technique which is based on wrapping. It is the wrapper’s responsibility to interact with the legacy system during each execution of the possible interaction scenario until the final response is obtained. In the concept of this black box approach, once the execution has started, the current state of the legacy system is unknown and the scenario cannot be determined. With this, a wrapper is designed to establish a dynamic execution of the case.
This approach is an automated one, which involves an interaction between the user and the legacy system which uses Finite State Automaton (FSA). In this scenario, the interaction state represents steps of the dialogue between the user and legacy system. This state can be associated with a screen template and with a set of actions to be performed on its fields. Summary Legacy system constitutes monolithic and big-sized applications. The idea behind had been to write a code given the system specifications.
However, it turned out to be composed of existing services. The idea of Web 2. involves a deeply service-oriented world in which news; instant messaging and blogging are exploited every day. Various approaches are available to attack problems involving legacy systems. One of the approaches which have been applied is the black box modernization which does not require the code to be changed. Black box modernization has been one of the techniques used to effectively migrate legacy systems from the old to a new platform through the encapsulation of the original system with a software layer which supports modern interface and hides the original. Conclusion
Service-oriented Software Reengineering has; indeed, help developers in the organization and in the conduct of reengineering of a tightly-coupled legacy information system into a loosely-coupled one. This has brought benefits in the modernization of legacy systems in the target system. The migration approach for exporting functionality has been a great help in the implementation of a legacy system as a web service. This kind of approach is tailored towards the transformation of web services which simply requires user interface adaptation according to the request/response interaction paradigm of the web services.