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Issue No. 02 - Second (2012 vol. 5)
ISSN: 1939-1374
pp: 192-206
Sylvain Hallé , Université du Québec à Chicoutimi, Chicoutimi
Roger Villemaire , Université du Québec à Chicoutimi, Chicoutimi
An increasing number of popular SOAP web services exhibit a stateful behavior, where a successful interaction is determined as much by the correct format of messages as by the sequence in which they are exchanged with a client. The set of such constraints forms a "message contract” that needs to be enforced on both sides of the transaction; it often includes constraints referring to actual data elements inside messages. We present an algorithm for the runtime monitoring of such message contracts with data parameterization. Their properties are expressed in {\rm LTL}\hbox{-}{\rm FO}^+, an extension of Linear Temporal Logic that allows first-order quantification over the data inside a trace of XML messages. An implementation of this algorithm can transparently enforce an {\rm LTL}\hbox{-}{\rm FO}^+ specification using a small and invisible Java applet. Violations of the specification are reported on-the-fly and prevent erroneous or out-of-sequence XML messages from being exchanged. Experiments on commercial web services from and Google indicate that {\rm LTL}\hbox{-}{\rm FO}^+ is an appropriate language for expressing their message contracts, and that its processing overhead on sample traces is acceptable both for client-side and server-side enforcement architectures.
Web services, runtime monitoring, temporal logic.

S. Hallé and R. Villemaire, "Runtime Enforcement of Web Service Message Contracts with Data," in IEEE Transactions on Services Computing, vol. 5, no. , pp. 192-206, 2011.
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