using processing instructions to provide meta informations?

[uu4hyu]

I intend to add some version information to my XML data.Since my tool evolves over the years so does my XML content/format.I might add some attribute to the root element, but I don't like this solution very much, as the version information is not an intrinsic property of my business class.An other idea is to introduce a versioned namespace for each new version.... I observed that MS used some \[code\]<?mso-application ... ?>\[/code\] PI to tag their documents.Is it a good idea to so and to introduce my own custom PI to carry my meta information?Is there a list of commonly used PI tags or how to design my own PI?To enable my tool to read former/outdated XML data I thing of plugging some XSLT transformation in front of my unmashaller to adapt former versions automatically.Thus my business class does not have to care about any outdated XML syntax.Any suggestions?Dieter.