GRASP

GRid based Application Service Provision

http://www.eu-grasp.net

Challenges

The main objective of the GRASP project is to enable the provisioning of business service in Grid environments. In order to achieve this objective the consortium members have developed a Grid based OGSI compliant (actually migrating towards WSRF) middleware which exposes all core functionalities for the design of ASP solutions.

The approach used by GRASP is based on a dynamic workflow management in order to discover on the fly, inside the Virtual Organization, the most well fitting component services to orchestrate for delivering composed business applications. The main challenges have been:

• Adequate description of the QoS. The QoS is described by Pre-SLA documents (are named Pre-SLA because they represent templates, that become real SLA at run-time after negotiation and service creation), for all services available in the Virtual Organisation. Each Pre-SLA document is written according to the Web service Level Agreement (WSLA) specification and contains a high level service description, customized for GRASP purposes, which has low level information about service metrics.
• Adeguate adversiting of the Pre-SLA documents. The Pre-SLA documents are stored in an UDDI repository and they are accessible via the Service Locator provided by GRASP platform.
• Dynamic orchestration process. The challenge was to allow the orchestration of different kind of services according to the QoS specified by the end user, at the negotiation time, by means of a Pre-SLA document. During the workflow, the Service Locator is used to query UDDI registry to retrieve the endpoints of the Service Instantiator in order to create the service with the specified QoS. A Service Instantiator is selected and the service creation phase is started. Obviously this phase involve all GRASP subsystems, increasing the complexity of the problem.
• Secure communication channels. The confidentiality of the messages exchanged between all services involved in the workflow process is addressed using GRASP security protocol.
• BPEL compliant Grid Services orchestration. We have used BizTalk server 2004 as BPEL engine to run the workflow process. BizTalk allows to orchestrate Web Services but it has some lacks to orchestrate Grid services. We have resolved the orchestration of Grid services via the support of reliable Web Services which acts as wrapper for the real service implementation. This Web services are the success key for creating business process BPEL compliant.