In this paper we present an approach for specification of exception handling and recovery of semantic web services based on OWL-S. We use standard fault handlers and compensation known for example from WS-BPEL to provide support for long running transactions. In addition to that, we introduce constraint violation handlers (CV-handlers) which allow a designer to define what situations are supposed to trigger an erroneous state and what are the appropriate recovery actions. Further, we introduce explicit recovery actions such as retry and replaceBy to recover from the failure and to restore a normal execution flow. By combining fault handlers, CV-handlers and standard event handlers it is possible to define ways of recovery for standard errors and for violations of constraints resulting for example from Service Level Agreements (SLAs).

Abstract. Web service-based applications are widely used, which has inevitably led to the need for proper mechanisms for the web service paradigm that can provide sustainable and reliable execution flows. In this paper we revise recovery techniques in OWL-S and show how semantic annotations may ensure seamless web service provision in a sophisticated way, such as, exploiting the ontology-based description of processes in order to dynamically find alternative services as substitutes for failed services. We also discuss the consequences of these semanticenabled approaches and point out required changes for integration in OWL-S.

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Online route planning services compute routes from any given location to a desired destination address. Unlike offline implementations, they do so in a traffic-aware fashion by taking into consideration up-to-date map data and realtime traffic information. In return, users have to provide precise location information about a route's endpoints to a not necessarily trusted service provider. As suchlike leakage of personal information threatens a user's privacy and anonymity, this paper presents PrOSPR, a comprehensive approach for using current online route planning services in a privacy-preserving way, and introduces the concept of kimmune route requests to avert inference attacks based on restricted space information. Using a map-based approach for creating cloaked regions for the start and destination addresses, our solution queries the online service for routes between subsets of points from these regions. This, however, might result in the returned path deviating from the optimal route. By means of empirical evaluation on a real road network, we demonstrate the feasibility of our approach regarding quality of service and communication overhead.