Link typing is the assignment of a link to a particular category in order to give a human or automated reader a clue about the implications of traversing that particular link. It would be more accurately termed “link categorization,” because it has very little to do with the computer science notion of data typing: the assignment of a type to data to identify the set of operations that can be performed on that data (integers can be added, subtracted, multiplied, divided; strings can’t, but can be concatenated, have substrings extracted, etc.).
Link typing clearly adds value to a link, and anyone discussing it agrees that it’s a Good Thing. Several link type taxonomies have been proposed, but no one I know of actually uses them for anything. In fact, none of the taxonomies I know of have improved on the one described twenty years ago by Randall Trigg in chapter four of his University of Maryland Ph.D. dissertation.
I have my own ideas about problems with various link taxonomies out there, such as the the values proposed for the XHTML 2.0 a element’s rel attribute, but for now I’d like to know if anyone else has done anything besides proposing new taxonomies since Trigg’s thesis. Do you know of any collection of links that actually have link types assigned to them? Even HTML with rel attributes on the a elements? (My limited research into that was not encouraging.) Has a generalized link taxonomy ever been proven useful, or are more application-specific ones such as the History and Treatment labels used in court case citations the only practical applications? Do you know of any any specialized ones besides court case citations?
Please post a comment here or e-mail me at firstname.lastname@example.org to let me know. And meanwhile, check out Trigg’s taxonomy.
What kind of link typing applications do you know of?