1. A method comprising: receiving, by a network traffic management apparatus, a web services description language (WSDL) document, wherein the WSDL document comprises a plurality of namespaces each corresponding to one or more of a plurality of Simple Object Access Protocol (SOAP) actions and is associated with a specified web service; converting, by the network traffic management apparatus, the WSDL document into a plurality of Extensible Markup Language (XML) Schemas each corresponding to at least one of the namespaces, wherein the XML Schemas are collectively representative of the WSDL document for the specified web service; subsequently receiving, by the network traffic management apparatus, a request in the form of a SOAP message from a client device to access the specified web service; determining, by the network traffic management apparatus, when the SOAP message is valid based on a comparison of the SOAP message against one or more of the XML Schemas converted from the WSDL document; and forwarding, by the network traffic management apparatus, the SOAP message to a web server hosting the specified web service when the determining indicates that the SOAP message is valid.