JISGA is a Jini-based service-oriented architecture (SOA) for Grid computing. In addition to the basic functionalities of a general Jini system, it has the following features:

• It gives users easy access to services by supporting an XML-based job description language (where a job, in general, is a composition of services).
• It automatically processes the job for the user by dynamically creating and executing the job processes.
• It allows both blocking and non-blocking job submission.
• It allows both sequential and parallel job processing.

Here the job that is submitted to JISGA is not a traditional software application written in some programming language or an executable code generated by a compiler, but a service-based application described by an XML document. The XML description document is based on Service Workflow Language (SWFL) and describes a job by specifying the workflow structure among the services of which it is composed. The automatic processing of such a job involves creating the Java code for the job, compiling the code, loading the class, executing the code, and sending the results to the job submitter.

Although JISGA is a Jini system, all its basic services are presented as Web services as well. The Jini lookup service and UDDI registry server coexist as the central mechanisms for publishing and discovering services. In JISGA the Jini lookup service provides the link between the Jini services and users and the UDDI registry server provides the link between Jini services and non-Jini users. Several assistant services or components are used in JIGSA:

• The Visual Service Composition Environment (VSCE) provides a graphical tool for generating composite service-based applications through a "drag-and-drop" interface. This generates an application described by an SWFL document.
• The Workflow Engine provides an execution environment for the composite applications described in SWFL. It allows both blocking and non-blocking job submission, and sequential and parallel job processing.
• A JobProcessor service mainly processes parallel jobs, which includes partitioning parallel jobs into sequential sub-jobs and then processing each sequential sub-job.
• JavaSpaces is a basic service provided by Jini, and its tuple-space is used in JISGA as a shared memory mechanism. JavaSpaces stores the job queues of the JISGA system, and also serves as an intermediary in communicating between distributed processes.
• A JSHousekeeper service is used to deal with certain tasks relating to the use of JavaSpaces, such as removing objects that have not been recently used, and updating the state of certain objects.
• A ServiceManager service is used to publish and remove services. The ServiceBrowser service is a support tool that allows a user to graphically and dynamically monitor the services within a JISGA system. Other supporting tools include service maintenance tools for service providers.
   

The following Figure depicts the architecture of the JISGA system. 

[Last Updated: 03/07/2003]