Seriously. Let’s step back for a second and try to work through to the core of the issue from a totally different angle.
Compare a set of predefined, fixed terms for certain domains, easy to use, etc. with a flexible and generic (hence, maybe, a bit more initial effort required) approach for annotating data, that is structured data on the Web. Sounds familiar? You’re right. I assume that you are aware of the old discussion around microformats vs RDFa, right? So, there we go …
Now, if one looks closer into the HTML 4 spec, one finds a bunch of link types, such as next, help, section, etc.; I’m gonna pick two, IMO, important sentences from there:
User agents, search engines, etc. may interpret these link types in a variety of ways. For example, user agents may provide access to linked documents through a navigation bar.
Ah, so the targeted consumer of the link is indeed a machine, not a human in the first place. Further:
Authors may wish to define additional link types not described in this specification. If they do so, they should use a profile to cite the conventions used to define the link types.
Ok, so there is a sort of extensibility mechanism defined in the HTML 4 spec as well. Very well! Or?
An analogy might help now to understand the point I’m trying to drive home, here. If you think back to microformats vs. RDFa, the same can be said about HTML 4 link types vs. RDF(a) …
HTML 4 link types as of section 6.12 of the spec are essentially the poor man’s semantic links, directly available in HTML. They are targeting machines (not human users in the first place), but are predefined in a sense and quite limited.
If you agree up to here by and large, then the question is really: what is the alternative? What technology out there, deployed, with community support, a set of tools available, etc. is available to represent, in a generic way (needed to write generic parser), any sort of typed link between two entities on the Web?
Note: credits go out to Juergen Umbrich with whom I discussed that issue yesterday evening and who inspired me writing the post …