Summary

The overall objective of the TAPAS project is to develop novel methods, tools, algorithms and protocols that support the construction and provisioning of Internet application services. The project will achieve the overall objective by developing QoS enabled middleware services capable of meeting Service Level Agreements (SLAs) between application services and will enhance component based middleware technologies such that components can be deployed and interact across organisational boundaries. The project will develop notations for expressing SLAs to enable specification of QoS, such as the availability as well as trust relationships. SLA trust specifications will be used for deriving service invocation primitives enriched with authentication, non-repudiation mechanisms, with or without the involvement of trusted third parties.

Description of the work
TAPAS is structured into four technical workpackages (WPs). WP1 will develop notations for expressing SLAs to enable specification of QoS as well as trust relationships. Model checking capabilities will be developed to support reasoning about QoS characteristics of components and their composition. The project will adopt UML as the language for the description, modelling and analysis and extend it with formally defined stereotypes and properties. SLAs are only useful if their compliance is enforced and monitored. To achieve this aim TAPAS will use SLAs not only as an inter-organisational contractual feature but also to govern component execution. WP2 will develop support architectures that provide QoS negotiation, establishment and adaptation facilities to enable component containers to become QoS enabled. SLA trust specifications will be used for deriving service invocation primitives enriched with authentication, non-repudiation mechanisms, with or without the involvement of trusted third parties. WP3 will implement key middleware services identified in WP2. Particular attention will be placed on the development of QoS enabled multi-party commumication (e.g. for supporting publish/subscribe communication, dynamic load balancing between replicated containers). Distributed applications with multiple senders pose several problems for network QoS; novel signalling methods and protocols for end to end QoS negotiation for resource reservation and feedback will be developed. Middleware services will be developed using open source application servers and widely used component technologies such as CORBA and JAVA. WP4 will evaluate results from the TAPAS projects by comparing them with current state-of-the-practice (e.g. an off-the-shelf CORBA or J2EE application server). Partners will build demonstrator applications with demanding QoS requirements such as hosting of an auction service.
Milestones and Expected Results
The final report on TAPAS architecture will cover the architecture of component oriented middleware for deployment in inter-organisation setting. Results will include model checking tool to support reasoning about QoS characteristics of components and their composition prototype, implementations using open source application servers and demonstrators. Preliminary results (milestones) will include reports on application hosting and QoS networking requirements.