WSDL

Assume you have some widgets you need built and you've decided that domestic cost of widget production is just to high. So, you've decided to farm out widget production to a subcontractor in some foreign country. The question is: ``How do you do it?'' You don't speak the same language, have the same business practices, have the same laws governing your businesses, and you don't share even a time zone. What is to be done? What would be ideal is if there existed some ``Esperanto'' in which your foreign colleague could describe how to contact them, what they will do, and what they will return to you. WSDL is such an ``Esperanto'' for the world of bits.

WSDL is a specification for a language grammar and semantics. A grammatical WSDL document describes a service one process provides for a second process. A grammatical WSDL document is written in such a manner as to be independent of the programming language the service is written in and independent of the programming language the process consuming the service. So, in the world of bits WSDL is an ``Esperanto,'' allowing geographically dispersed processes which ``speak'' different language to communicate and exchange services.

As ``Esperanto'' is based upon words common to all European languages, so WSDL is based on XML, a language common to most programming languages. A WSDL document is in fact an XML document. But the opposite is not true, an XML document is not a WSDL document. WSDL introduces some grammatical and semantic structures to those present in XML. As one might imagine, when dealing widgets on the high seas in Esperanto there might evolve some specialized terminology which is specific to international widget trade, terminology which is not present in the base languages from which Esperanto draws. Similarly, WSDL has evolved grammatical and semantic structures not present in XML to deal with the particulars of language independent inter-process communication.

So what exactly are the various parts of grammatical WSDL document? They are the following:

• Type Description Component
• Message Description Component
• PortType Description Component
• Binding Description Component
• Service Description Component

Each of these description components has a particular role in a grammatical which we'll now outline.

• Type Description Component
• Message Description Component
• PortType Description Component
• Binding Description Component
• Service Description Component