Savas Parastatidis

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Top Stories by Savas Parastatidis

There has been much debate lately on what exactly WSDL's purpose is, and much of that debate has focused on whether WSDL is an interface definition language (IDL), or whether WSDL is better used to specify message-level contracts (without any associated operational semantics). In this article we present an argument that dealing with WSDL as a message-level contract description language is the right way to go for building loosely coupled Web services. Interfaces and Contracts Before we delve into the specifics of how WSDL should be used, we need to understand the difference between a classic interface and a contract. By understanding the different problems that each solve we can begin to form a picture of when it is appropriate to use one or the other. Let's start by briefly recalling exactly what is meant by an interface. In an object-oriented view of the world, appli... (more)

Stateful Interactions in Web Services

In July 2003 a consortium of Web services vendors released the Web services Composite Application Framework (WS-CAF) to the community. WS-CAF is comprised of three specifications that together provide a means of reliably composing individual Web services into larger aggregate applications. The cornerstone of this suite is the management of stateful interactions between Web services that is the domain of the WS-Context specification. WS-CAF was subsequently submitted to OASIS and an effort to standardize the framework is currently underway. In January 2004 a group of industry and... (more)

Introducing Open Grid Services

In June 2003, the Global Grid Forum (GGF) adopted the Open Grid Services Infrastructure (OGSI) specification as a GGF standard. OGSI is essential to the Open Grid Computing vision as it is the foundation on top of which the building blocks of future Grid applications will be placed. Those building blocks, the Grid services, are being defined by various GGF working groups, with the Open Grid Services Architecture (OGSA) working group orchestrating the entire process. This article introduces OGSA, presents the OGSI specification, and discusses the significant role of Web service s... (more)