There is only one file type that uses the .WSDL extension:
Web Services Description Language File
Information file written in the WSDL XML format, which is maintained by W3C.org; provides descriptions of "ports," or network endpoints, on the Internet or another network; often used for publishing data feeds and specifications for remote application access.
WSDL files describe information such as the types (data type definitions), messages (the data communicated), operations (actions), and protocols used by the service. However, they often describe this information at an abstract level. Therefore, WSDL files commonly require another file that provides the bindings for the service's parameters. This allows WSDL files to be reused with multiple different bindings.
Any number of technologies can be used for interfacing with WSDL services. For example, WSDL files are used by ASP.NET, C/C++, and Java applications.
NOTE: Microsoft Visual Studio includes a program named the Web Services Description Language Tool (Wsdl.exe), which can be used for creating WSDL files.
Updated: October 30, 2011