The selection of a Web service operation provides requirements that result from the functional service description like WSDL or WADL. These descriptions provide the name and type of the operation, the associated parameters and their data types. Additional requirements regarding semantic information are not in scope of these functional description languages. Therefore the use SAWSDL[9] or SA-REST[10] is adequate to integrate further semantic information, such as a reference to a concrete domain in which the provided functionality can be used. However, the minority of available services are described with additional semantic information using SAWSDL or SA-REST. Thus, we focus on the more important matching of the functional descriptions based on similarities between the interfaces. We argue that a semantic matching cannot replace the syntactical comparison of the interfaces, which is in all cases required.