Ogsi practicalview
- 1. Prof. Neeraj Bhargava Pooja Dixit Department of Computer Science School of Engineering & System Sciences MDS, University Ajmer, Rajasthan, India 1
- 2. OGSA aims at addressing standardization (for interoperability) by defining the basic framework of a grid application structure. the OGSA standard defines what grid services are, what they should be capable of, and what technologies they are based on. OGSA, however, does not go into specifics of the technicalities of the specification; instead, the aim is to help classify what is and is not a grid system.It is called an architecture because it is mainly about describing and building a well-defined set of interfaces from which systems can be built, based on open standards such as WSDL. The objectives of OGSA are: ◦ Manage resources across distributed heterogeneous platforms. ◦ Support QoS-oriented Service Level Agreements (SLAs). The topology of grids is often complex; the interactions between/among grid resources are almost invariably dynamic. It is critical that the grid provide robust services such as authorization, access control, and delegation. ◦ Provide a common base for autonomic management. ◦ Define open, published interfaces and protocols for the interoperability of diverse resources. ◦ Exploit industry standard integration technologies and leverage existing solutions where appropriate. The foundation of OGSA is rooted in Web services, for example, SOAP and WSDL, are a major part of this specification. 2
- 3. OGSA is the blueprint, OGSI is a technical specification, and Globus Toolkit is an implementation of the framework. OGSA describes and defines a Web-services-based architecture composed of a set of interfaces and their corresponding behaviors to facilitate distributed resource sharing and accessing in heterogeneous dynamic environments. A set of services based on open and stable protocols can hide the complexity of service requests by users or by other elements of a grid. Grid services enable virtualization; virtualization, in turn, can transform computing into a ubiquitous infrastructure that is more akin to an electric or water utility. OGSA relies on the definition of grid services in WSDL, which, as noted, defines, for this context, the operations names, parameters, and their types for grid service access. Based on the OGSI specification, a grid service instance is a Web service that conforms to a set of conventions expressed by the WSDL as service interfaces, extensions, and behaviors. Because the OGSI standard is based on a number of existing standards (XML, Web services, WSDL), it is an open and standards-based solution. This implies that, in the future, grid services can be built that are compatible with the OGSI standard, even though they may be based on a variety of different languages and platforms. 3
- 4. Proposed OGSA grid service interfaces* 4
- 5. Service capabilities (that is, the services offered by a particular company or organization) are widely used in existing Web services solutions. Likewise, grid services are characterized by the capabilities they afford. A grid service capability could be comprised of computational resources, storage resources, networks, programs, databases, and so on. A grid service implements one or more interfaces, where each interface defines a set of method operations that is invoked by constructing a method call through, method signature adaptation using SOAP. Like the majority of Web services, OGSI services use WSDL as a service description mechanism. There are two fundamental requirements for describing Web services based on the OGSI: ◦ The ability to describe interface inheritance—a basic concept with most of the distributed object systems. ◦ The ability to describe additional information elements with the interface definitions. 5