Model-driven semantic Web service composition

As the number of available Web services increases there is a growing demand to realise complex business processes by combining and reusing available Web services. The reuse and combination of services results in a composition of Web services that may also involve services provided in the Internet. With semantically described Web services, an automated matchmaking of capabilities can help identify suitable services. To address the need for semantically de-fined Web services, OWL-S and WSML have been proposed as competing semantic Web service languages. We show how the proposed semantic Web service languages can be utilized within a model-driven methodology for build-ing composite Web services. In addition we combine the semantic-based discovery with the support for processing QoS requirements to apply a ranking or a selection of the candidates. The methodology describes a process which guides the developer through four phases, starting with the initial modelling, and ending with a new composite service that can be deployed and published to be consumed by other users.

Weaving of UML sequence diagrams using STAIRS

In this report we explore aspect-oriented modeling for UML 2.0 sequence diagrams. We ensure that the aspect weaving is semantics-based by using a formal trace model for sequence diagrams. A major challenge is to handle unbounded loops which produce infinite traces. We establish a systematic way to permutate and rewrite the original loop definition so that the weaving in many typical cases can be performed on a finite structure. We prove that it is always sufficient to consider a loop with upper bound relative to the pointcut definition to discover if the loop has infinitely repeating matches. A running example illustrates the approach and a prototype weaving tool is being implemented

Evaluation of the QVT Merge Language Proposal

-STF90 A05045This report has identified 29 weighted evaluation criteria representing desired properties of a model to model transformation language. These criteria have been used to evaluate the current QVT Merge specification. We have so far only been able to evaluate 21 of these criteria, mainly due to missing tool support. Some of the criteria are considered absolute in the sense that missing to fulfil such a criterion is considered a failure. The 21 evaluated criteria give a score of 59 out of a maximum possible score of 68 (language-based + example-based testing). We have also compared the QVT-Merge submission with the QVT-Compuware/Sun submission and at the time being the QVT-Merge seems to be the preferred one due to more support on the absolute criteria and better easy-to-use score. Eight transformation examples for solving six different transformation tasks have given a lot of insight on the ease of use criteria for both simple and complex transformations. When defining transformations using QVT Merge we believe that a lot of effort may be required in order to define the source and target  metamodels. The evaluation in this report could be improved by using the reference examples with alternative approaches published in the literature. An available QVT-Merge tool is necessary in order to provide evaluations of all the suggested criteria. In order to further investigate the usability of the graphical notation, we need to define more of the transformation examples graphically. Only one of the examples has been specified graphically in this version. The current evaluation has been done by a single evaluator who has only reviewed the transformation code that was written by somebody else. The evaluation will be further improved by incorporating input from other evaluators as well as evaluation from those who wrote the transformation code. Oppdragsgiver: EU Commissio

Can Graph Transformation Make Aspect Languages for BPEL Redundant?

The aspect language AO4BPEL has been introduced as a way to modularize cross-cutting concerns in Web service compositions that are specified in BPEL. AO4BPEL can be difficult to understand and to write for non-XML experts. This paper explores if algebraic graph transformation rules can be used to specify BPEL aspects at the modeling level, and make new aspect languages like AO4BPEL redundant. Three AO4BPEL examples, taken from the literature, are used to test the suitability of graph transformation as a means to simulate BPEL aspects

A Service Composition Construct to Support Iterative Development

Development of composed services requires a continues adaptation of the composed service to the changing environment of offered services. Services may no longer be available or may change performance characteristics, price, or quality of service criteria after they have been selected and used in a composition. The replacement of such a service requires a good understanding why this service got selected in the first place. This is hard to accomplish as it is known from software maintenance. Therefore we propose an approach where the conceptual task implemented by a selected service as well as the relationship between task and selected service is explicated and maintained during the complete life cycle of a composed service. This covers the design of the composition, derivation of service search criteria, and the execution of the composed service. The approach has been validated by an implementation in the Service Composition Studio (SERCS) supporting the iterative development of composed services