What is a Defined Data Model?
What are the requirements for sufficiency?
If we're talking about extension modules, we might want to know things such as:
whether they can be combined with other, independently created extensions
whether XML element and attribute order is used to convey meaning (eg. author listing, is the first the primary author)
which fields from the extension are uniquely identifying for the object they describe
The RSS 1.0 approach to this was to use RDF conventions. This meant that all extension modules could be treated similarly:
in RSS 1.0's abstract model, independent extensions could be freely mixed (though there were syntactic restrictions on what you could write -- only one top level extension element was allowed in item)
in RSS 1.0, via RDF, we specified that XML element and attribute order was never used to convey meaning (hence the rdf:Seq table of content structure which preserved ordering of items).
In RSS 1.0, modules defined RDF properties and classes, so we could use RDF Schema and OWL to look up metadata about new kinds of property, for example to find out if they were uniquely identifying.
Whether or not there is a !echo mapping to RDF, it is likely we will want some way to get answers for these questions about extension models. --danbri
Related was originally a simple linking mechanism. Maybe we should consider it as a simple use case of DefinedDataModel + SyntaxExtensionMechanism + ComponentBlog. Please help to refactor the issues there to better understand the issues facing the larger issue of Semantic Web Logs.