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Web Service Description Language (WSDL) is being increasingly used to specify web service interfaces. Specifications of this type, however, are often incomplete or imprecise. For example, cursory examination of the WSDL file for Amazon’s E-Commerce Web Service reveals that it often uses a less specific type where a more specific type is applicable, or declares that elements could be missing where other documentation indicates that they are required. Further, specifications reflecting the temporal relationships between operations are completely missing, which is not surprising since they are not supported by the current WSDL standard. These problems in WSDL specifications can cause tools that use them to perform poorly or unreliably, and can mislead developers who rely on them. To address these problems, in this paper we present an automated methodology for collecting static and dynamic information about a web service, and using this information to suggest improvements to the WSDL file as well as providing complementary information about the behavior of the web service that cannot be captured by the WSDL. Additionally, we present the results of two case studies performed on commercial web services that show our methodology can find problems in WSDL files and suggest improvements.