Why is there a Schema in my WSDL?

i cannot understand what a schema is doing in a wsdl document ? Is it some kind of a definition that defines the structure of开发者_如何学C the xml tags ?

A WSDL document specifies the top-level operations exposed by the web service. Those operations, in turn, refer to schema types which define the data that gets passed back and forth when those operations are invoked. So there's a schema embedded in (or referred to from) the WSDL document.

You may have noticed that the schema is inside of the <wsdl:types> element.

Yes, the schemas in the types element define the types used in the rest of the WSDL. In particular, they define the types used as message types.