Give an overview of GIOBUS GT3 programming modelSolutionThe

Give an overview of GIOBUS GT3 programming model.

Solution

The Globus Toolkit is an open source toolkit for grid computing developed and provided by the Globus Alliance.

A Grid Service is a Web Service which conforms to a set of conventions (interfaces and behaviours) that define how a client interacts with a Grid service.

The basis for Grid Services are Web Services - a network accessible functions that can be invoked via a well-defined remote interface.

Web Services enable service-oriented architec- tures : — internet-based applications with loosely-coupled clients and servers — the most common implementation of web services works in a simple Request-Response paradigm using the HTTP for transmitting messages

• Web Services Architecture • Web Services are layered on the top of standard transfer protocols for transmitting messages: UDDI Service Discovery (Universal Description, Discovery and Integration) Service Description (Web Services Description Language) Service Invocation (Simple Object Basic Protocol) WSDL Transport (over TCP/IP)

Grid Services - standard Web Services with improved characteristics. • Grid Services are defined by the Open Grid Service Architecture (OGSA). • Grid Services are specified by the Open Grid Services Infrastructure (OGSI). • Globus Toolkit 3 (GT3) is an implementation of everything what is specified in OGSI, and therefore everthing what is defined in OGSA.

The OGSA defines a common, standard, and open architecture - a distributed system framework based on OGSI - for grid-based applications. • The Goal - standardize services for grid applica-tions by specifying a set of interfaces and conven-tions for these services. • A Grid Service Interface corresponds to portType in WSDL.

The OGSI defines mechanisms for creating, managing, and exchanging information among entities – Grid Services. • The OGSI gives a formal and technical specifi-cation of what a Grid Service is and how it works.

OGSI Improvements : Stateful and potentially transient using a factory/instance model GSH & GSR allow to refer to Grid Service instances Grid Service Handle – URI Grid Service Reference – WSDL file Lifetime management instances can be created and destroyed at any time