The sub-project of the iCite net I'm working on right now includes in it a data model for blog rolls. This will be used to output blogroll data in a variety of formats.

It seems like it'd be good to support OPML as an output format, though I've never really done anything with OPML myself. So, I have a few questions.

First, with OPML outline attributes like xmlURL and htmlUrl, these are kind-of a profile in the sense that people use them, but there is no absolute spec anywhere that says they have to be used, or that other attributes can't be added. Is this right?

Basically, I want to add another attribute or two that are specific to this sub-project. Plus, since some folks are using XFN data in their blogroll listings (and this is to be accounted for in my data model), the XFN "rel" data would also seem a natural fit for an additional attribute.

(Although, another interesting question: since each XFN rel attribute contains a list of data with one or more items, e.g., rel="colleague met", wouldn't it be useful, in theory, to have each item treated as a full-fledged data attribute in certain, non-HTML, data representations? Hm....)

Possibly along these lines, I notice that many folks have their blogroll divided into sections (example: Jake's Radio 'Blog blogroll currently has about 10 sections). In some blog systems, the sections may be implemented as separate blogrolls, but, from the point of view of my data model, it makes sense that blogroll listings be collected as a single set of listings optionally associated with one or more listing categories.

So, it looks like the convention is to use the outline model, with each blogroll section hierarchically containing a subset of blogroll listings (ex: Jake's OPML). Anyone know of counter examples, i.e., having a category attribute in each listing?

Actually, being that OPML is XML, the hierarchical outline model is better in the sense that hierarchy is the natural way to represent sections in XML. But, I thought this OPML vernacular would be something other folks would know more about and maybe could fill me in a little.

I'm also thinking it might be nice to output blogrolls as XOXO Extensible Open XHTML Outlines (which may be supported by another view in this same sub-project), but I haven't yet seen a clear example of a blogroll in XOXO. So, got XOXO blogrolls, anyone?