assoc. prof., dr. Vladimir Dimitrov University of Sofia, Bulgaria

Abstract Service Oriented Architecture (SOA) is the most attractive approach in the last years for development of highly distributed integrated enterprise applications. SOA is based on web services specified in WSDL and registered in repositories with UDDI. The basic mechanism for message exchange between services is SOAP. BPEL is used for specification of business processes described as networks of communicating services. Development of SOA applications needs of: process orchestration software for specified in BPEL business process; mediation software for exchange of messages between services; and repositories for registration and discoveries of services. Grid is service oriented; it has repositories for service definition and discovery; but still there are no wide accepted mechanisms for orchestration and mediation. One more problem is end user communication which has to be supported by Grid portals. In this paper IBM approach to SOA is investigated and its applicability to Grid for scientific applications is discussed.

SOA by IBM IBM defines SOA as: “… an architectural style for creating an Enterprise IT Architecture that exploits the principles of service orientation to achieve a tighter relationship between the business and the information systems that support the business.” From this definition is clear that SOA is following principles of service orientation. SOA is an architectural style. The main achievement of SOA is tighter relationship between the business and the information systems that support the business. From IBM point of view SOA is applied for development of Enterprise IT Architecture that integrates business information systems.

SOA Terminology To clarify IBM SOA we give the definitions of used terms: “…service-orientation is a way of integrating your business as a set of linked services.” Or in other words service-orientation looks at business (business processes) as structured in services linked with each other. “…a service is a repeatable task within a business process.” This definition of the service as repeatable task is not precise. From here it is not clear what is granularity of this repeatable task. Right understanding of service granularity is the condition for success or fail of a SOA based project. If the services are very small much execution time is spend for communications. If services are very large they are complex and hardly manageable. The experience shows that well designed business services are well granulated services. What the business name a service it is a service. It is possible some system services to appear later in the development, but they only support software design and implementation – they do not extract any functionality from the business services, they utilize implementation of some functionality of business services. This approach is in contradiction with IBM’s Service-Oriented Modeling and Architecture (SOMA) approach, but comments on this topic are out of scope of this paper. “A composite application is a set of related and integrated services that support a business process built on SOA.” This means that composite application is a SOA implementation of business process.

SOA Standards The language is Business Process Execution Language (BPEL). This is a XML based language developed by OASIS consortium. In BPEL the business process is described as communicating web services. Web services are specified with Web Services Description Language (WSDL) – XML based description language of web services. In WSDL are specified: operations on web service, messages that web service interchange through its operations and where web service resides. Message exchange among web services follows Simple Oriented Access Protocol (SOAP) – exchange protocol of XML messages over a transport level protocol usually HTTP. Web services are registered (published) in repositories supporting Universal Description, Discovery and Integration (UDDI) protocol.

Sample View of a WebSphere Business Modeler Diagram

WebSphere Integration Developer Process Diagram

Example of Interaction of Process Server/ESB with WSRR

Grid by IBM IBM defines Grid infrastructure objectives as:  Creates a virtual application operating, storage, and collaboration environment;  Virtualize application services execution;  Dynamically fulfils requests over a virtual pool of system resources;  Offers an adaptive, self-managed operating environment that offers high availability.

IBM Grid Solutions Network Grid Infrastructure for File Downloading. A network of distributed file servers enables an optimized download upon a client request for a particular file. The system is built as a grid of dispersed download servers. This solution primarily addresses the enterprise optimization business driver. This is the first IBM project on Grid computing. Grid vision presented here is very much like that one in [20]. From architect point of view Grid consists of Grid coordinator and Grid nodes. Grid coordinator (downloadGrid management center) accepts jobs and distribute them work nodes. In this case the job is to download some file from the repository (Registration Module & Data Unit Distribution Module). The Grid coordinator creates optimized downloading plan using Feedback and Statistical Module and Optimized Plan Module. The system information database can be replicated by Replication Module. This system implements GSI as security mechanism. Public Health Data Grid. A network of servers stores digital mammographies that are associated with explanatory notes and comments about each image. The system is built up as a grid-enabled federated database. This solution primarily addresses the productivity and collaboration business driver. The Grid element is Globus Toolkit 3.0 Computational Grid Infrastructure for the Upstream Oil and Gas Industry. A network of servers provides a high-performance virtual cluster to process oil field exploration applications, such as upstream petroleum processing. This solution helps to accelerate the business process and to optimize the enterprise. In this solution Globus Toolkit is used, but job submission is organized through Grid Portal. The last one automates user interactions with the Grid environment.

IBM Grid Solutions Industrial Sector Data Grid. A network of data servers enables users to access heterogeneous files in different systems, regardless of where they are. This solution primarily addresses productivity and the collaboration business driver. This solution is for data intensive Grid computing how is presented in previous examples. Computational Grid Infrastructure for Trading Analysis. A network of desktops and servers helps to gain the necessary computing power to run long and complex algorithms that are required for trading analysis. This solution helps to accelerate the business process and to optimize the enterprise. In this example IBM WebSphere MQ is used to connect client software to DataSynapse GridServer. The last one is cluster management software. The most important idea here is that IBM WebSphere MQ can be used as mediator in standard client- server architecture between the client, Grid software and the server. Computational Grid for the Consulting Industry. A solution aims to release the computation consumption of an IBM mainframe by submitting heavy algorithm jobs to grid nodes. This solution addresses IT optimization as its primary business driver. This solution is like one presented above.

Grid SOA Application Architecture

How SOA could be supported by Grid? SOA standards are: BPEL, WSDL, UDDI, SOAP, and XML. This means that these standards have to be implemented in Grid. Processes running on Grid have to be specified in BPEL and orchestrated by specialized nodes. Such candidate orchestration software for these nodes can be WebSphere Process Server, JBoss, Oracle BPEL Process Manager, or BEA WebLogic. The most advanced orchestration software is WebSphere Process Server. It can be integrated in Grid environment, but it works in combination with other WebSphere products, so it is hardly to imagine that nowadays WebSphere Process Server can be the software for the orchestration node. Oracle BPEL Process Manager and BEA WebLogic have just a same problem – they are not open enough to be well integrated with software not deployed by their vendors. The only realistic candidate is JBoss. Its problem is that it is not mature enough for serious usage.

How SOA could be supported by Grid? It a standard for repositories to support WSDL and UDDI, so services could be registered and searched in Grid. The problem from mediation point of view is how effectively to support message exchange between services. ESB concept is based on the fact that it works in cluster where the communications are highly reliable and are at a level higher than inter cluster exchange. It is clear that first SOA applications will be cluster based. Grid is diverging to SOA support environment, but many more work has to be done before we will have an environment in which processes are orchestrated on overall Grid infrastructure – when process services are geographically distributed.

Can Grid be reengineered in SOA? Nowadays SOA is an ultimate architecture for development of distributed system. Grid software is older and does not have this architecture. It is possible to develop adapters for Grid software and start orchestrate it, but it is not sensible, because it would not run effectively. The only way is to redevelop Grid software in SOA which is very expensive.

Conclusion What is the realistic scenario for development of SOA based Grid application? First, processes have to be executed as much as possible on one cluster. A worker node has to be specialized for orchestration with software like JBoss. Application software has to be reengineered for SOA. For this reengineering currently available tool like that one of WebSphere can be used. Some kind of ESB has to be developed for message exchange between services in the cluster. This ESB like software can be MPI based. At University of Sofia we are doing research on deployment of SOA based applications for Grid. Currently, we are investigating deployment of BPEL processes to JBoss. There are many technical problems. Our intention is to demonstrate some SOA based CMS software.

Thank for Your Attention! Questions?