I am asking this question predominantly in the context of a REST/XML web service API (media type "application/vnd.mystuff+xml"), but perhaps the question is still valid for SOAP based web services.
In the event that the XML schema that describes the vocabulary of our resources/payloads changes, how should I best indicate to the client they should use/expect a newer version of the XML schema?
Should we include a version identifier in the root element like this:
<mything xmlns="http://mycompany.com/yadda" version="1.0">
or should we just reference the XML schema like this:
<mything xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:SchemaLocation="http://mycompany.com/yadda/1 yadda-1.0.xsd"
xmlns="http://mycompany.com/yadda">
or both?
<mything xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:SchemaLocation="http://mycompany.com/yadda/1 yadda-1.0.xsd"
xmlns="http://mycompany.com/yadda"
version="1.0">
Is it common practice to send an XML payload that references an XML schema?