XSD is used to validate a document conforms to some standard. Say you run a legal document firm and you receive Form Foo from 100 different clients, XSD will h

XSD is used to validate a document conforms to some standard. Say you run a legal document firm and you receive Form Foo from 100 different clients, XSD will handle validating that they are conforming to the standard for you. XSL is an umbrella for a few things, most interesting is XPath which is a super fast query language for xml documents. SOAP is just worthless. WSDL is nice though, it compiles a web service API to source code so you get a nice layer of abstraction around what you're writing to.