Vijaykanth sadhasivam 990021674
Vijaykanth Sadhasivam 990021674
Critique on Turner, M.; Budgen, D.; Brereton, P. Turning software into a service IEEE Computer, 36(10), 2003, pp. 38- 44
Summary:
This paper describes Software as a service (SaaS) model, in which services are composed dynamically by binding lower-level services. It describes a Web services stack framework to realize this model and how the stack can be extended to obtain a service integration layer.
SaaS Advantages:
➢ Overcoming limitations in software use and deployment
➢ Opens up new markets for both small and large service providers.
➢ Dynamic creation and deployment of new services that use existing ones
Service Integration Layer:
To achieve the above objectives, the author proposes a demand-led service model that has a Service Integration Layer above the transport layer. This layer incorporates four key functions.
➢ Service description: matches client needs to appropriate and available services.
➢ Service discovery : To locate appropriate services according to client requirements and selection criteria and to negotiate agreement on the terms and condition for supplying a service
➢ Service delivery: Consists of service Invocation, Provision and Suspension.
➢ Service composition: Composing of service from lower-level services using existing rules for the services.
Web-services stack framework & Realizing the Service Integration Layer:
The author describes a framework, consisting of several layers with each layer using the services of the layers below it. The stack can be divided into three vertical sections based on whether they use WSDL, DAML-S or ebXML specifications. There are several gaps in the described stack.
➢ Service description: WSDL and CPP (in ebXML section) describes only technical aspects of the transactions and does not describe the function the service provides semantically.DAML-S provides some of these functions but it currently lacks extensive ontologies and support for it is also limited.
➢ Service discovery: UDDI and ebXML do not allow semantic descriptions and searching which limits SaaS model‘s dynamic discovery capabilities.UDDI must be extended along with DAML-S to provide with a registry capable of semantic matching.
➢ Service Negotiation: None of the protocols in the current framework allow for fully automated negotiation between the client and the provider.
➢ Service Delivery: Current protocols cover only web service’s basic invocation and provision and not monitoring and suspension of the services.
➢ Service Composition: Current protocols lack functionality to support complex web services composition dynamically and long running transactions
CRITICAL QUESTIONS:
1) What tools are being developed to support DAML-S and provide semantic description and searching capabilities so that services can be discovered dynamically?
2) How do we integrate the various sections described in the framework to achieve interoperability and fill the significant gaps in the stack
3) How do we extend the current protocols to provide automated negotiation ,service monitoring and suspension and functionality to compose complex web services dynamically
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