Difference between data and metadata

From a Web Services point of view, I believe what travels on the wire is data (e.g. SOAP messages in HTTP envelopes). ; What describes what goes on the wire is metadata (WSDL, WS-Policy, CDL). ; In a few instances metadata might appear on the wire, but generally only to facilitate future interactions, not to make that particular exchange work.

 

I believe WSDL is purely metadata, through the thought experiment.  If I took the WSDL away, would the described on-the-wire exchange still be able to occur?  In almost all cases an omniscient coder could still craft the required messages and successfully exchange them. ; The metadata, in its various flavors, is not strictly necessary to the successful exchange, but describes different parts of the exchange in formats that allow an ignorant coder (e.g. a toolkit) to raise it’s level of awareness towards omniscience.

 

We all know there are limits to today̵7;s metadata formats, especially in terms of legal obligations and business purpose, that will continue to be indescribable.  This information is missing (in machine-readable form) and yet the exchange can still take place, thus it also falls under my definition of “metadata”;.

 

Hope this helps.

 

 

Dear all,

I am kind of confused about the definition of metadata in the context of web services and would be very grateful for any clarification.

First question would be, if the WSDL-specification already is metadata regarding to my web service or primary a definition of my web service ( i.e. the data which is enhanced via metadata)?  WS-Policy and WSDL-S annotations clearly seem to be metadata, but what about a description of the choreography with ws-cdl or a definition of security mechanism with ws-security? data or metadata?
how would you classify standards like ws-management and ws-reliablemessaging?

In the standard I could not find any clear specification of this term...

Thanks and kind regards,
Christian