When working with and reusing Web services publishers will often maintain the different parts of services in separate locations.

Structures and types will often be defined in seperate XSD schema documents. Static reusable schema instances will be published in XML resources. Mappings between documents is handled XSLT transforms. Interfaces that use schema defined types to declaring message forms and operations; Bindings that declare how to use such interfacs; Services that encapsulate bingdings; and ports that declare where to find live application instances are all expressed in WSDLs.

Understanding Web service applications is easier when you can inspect the documents where types and operations are declared and defined.