The potential of communication networks and middleware to enable the composition of services across organizational boundaries remains incompletely realized. In this paper, we argue that this is in part due to outsourcing risks and describe the possible contribution of Service-Level Agreements (SLAs) to mitigating these risks. For SLAs to be effective, it should be difficult to disregard their original provisions in the event of a dispute between the parties. Properties of understandability, precision, and monitorability ensure that the original intent of an SLA can be recovered and compared to trustworthy accounts of service behavior to resolve disputes fairly and without ambiguity. We describe the design and evaluation of a domain-specific language for SLAs that tend to exhibit these properties and discuss the impact of monitorability requirements on service-provision practices.

The Java-UML Lightweight Enumerator (JULE) tool implements a vitally important aspect of the framework for software tool certification- test suite generation. The framework uses UML models as the test inputs for the bounded exhaustive-testing approach. Within a size bound for the metamodel types, JULE enumerates only the set of non-isomorphic models in the form of relational structures. These models are classified into two sets- demonstration and counterexample- using Binary Decision Diagrams (BDDs). The power of JULE lies in its model enumeration and its use of a high-performance grid infrastructure. Hence, JULE efficiently generates a very small test suite while increasing the bound on the input size to the extent that is practical for certification purpose.

If an organization depends on the service quality provided by another organization it often enters into a bilateral service level agreement (SLA), which mitigates outsourcing risks by associating penalty payments with poor service quality. Once these agreements are entered into, it becomes necessary to monitor their conditions, which will commonly relate to timeliness, reliability and request throughput, at runtime. We show how these conditions can be translated into timed automata. Acceptance of a timed word by a timed automaton can be decided in quadratic time and because the timed automata can operate while messages are exchanged at runtime there is effectively only a linear run-time overhead. We present an implementation to derive on-line monitors for web services automatically from SLAs using an Eclipse plugin. We evaluate the efficiency and scalability of this approach using a large-scale case study in a service-oriented computational grid.

SLAng is an XML language for defining service level agreements, the part of a contract between the client and provider of an Internet service that describes the quality attributes that the service is required to possess. We define the semantics of SLAng precisely by modelling the syntax of the language in UML, then relating the language model to a model that describes the structure and behaviour of services. The presence of SLAng elements imposes behavioural constraints on service elements, and the precise definition of these constraints using OCL constitutes the semantic description of the language. We use the semantics to define a notion of SLA compatibility, and an extension to UML that enables the modelling of service situations as a precursor to analysis, implementation and provisioning activities.

We present an approach to managing formal models using model driven architecture (MDA) technologies that deliver analysis techniques through integration with the design tools and repositories that practitioners use. Expert modeling knowledge is captured in domain-specific languages and meta-model constraints. These are represented using UML (Unified Modeling Language) and collocated with designs and analysis models, providing a flexible and visible approach to managing semantic associations. The approach relies on standards to permit deployment in multiple tools. We demonstrate our approach with an example in which queuing-network models are associated with UML design models to predict average case performance.