I’ve always thought that what makes del.icio.us so successful despite a lot of recent competition is that it exemplifies the same kind of thinking Tim Berners-Lee described in his “Axioms of Web Architecture” as the “Principle of Least Power,” or what the designers of the Internet called “end-to-end architecture.” Instead of trying to build a powerful, heavyweight system that would anticipate a user’s every need, Joshua and company have been building an extremely simple, general service that can be endlessly adapted and easily plugged into other systems.
The variety of “meta” tagging schemes del.icio.us users have evolved is great evidence of this. Probably the best known example, the “for:” tag prefix, has actually become commonly enough used that Joshua and company have given it formal recognition within the system, but there are lots of other schemes in usage. I’m a frequent user of “cite:” (to attribute links I get from other people), for example, and now that I’ve been using the new del.icio.us media support to run an ad-hoc podcast, I’ve been exploring the use of “meta” tags for music metadata.
It was this last usage that led me to an epiphany. As I started tagging songs I posted with metadata like “artist:thenational” and “soundslike:afghanwhigs,” I realized that I was, in effect, creating triples and using tags as a sort of poor man’s RDF.
For those who aren’t familiar with RDF (which is probably almost everyone, since RDF is rarely explained well), it might be helpful to pause for a moment to explain the concept of triples. The first thing you need to understand is that RDF is an attempt to standardize the way we represent the relationships between data, just as XML standardizes the way we represent that data’s structure. Information in RDF is expressed as a series of statements that each have a subject, verb, and object–triples. For example: The National [subject] sounds like [verb] the Afghan Whigs [object].
A collection of these statements is referred to as a “triple store,” which can be understood as a sort of ad-hoc database. While traditional relational databases require that new properties be formally added to the model either by adding new columns to an existing table or by adding additional tables, adding a new property in RDF is as simple as asserting in a triple that value X is a certain property of entity Y.
So, then, a collection of del.icio.us links containing “meta” tags can be thought of as a triple store. “Interesting,” you may say, “but why should I care?” Which is a very reasonable question given RDF’s current track record of real-world usefulness.
Well, as it happens, my del.icio.us/triple store epiphany has given me an idea for a Cocoalicious feature (yes, I do plan to release a new version of Cocoalicious some day). It occurred to me that I could turn Cocoalicious into a sort of free-form database by treating “meta” tags as triples, compiling a list of the implicit properties contained in these triples, and allowing the user to add columns displaying the values of those properties for each post to the main table view (probably by way of a context menu like the one you get by right-clicking on the iTunes column headers). That way the user could implicitly add his or her own metadata the Cocoalicious model, which could be used to sort and query the post list.
I suppose this feature might be too esoteric to be useful to that many people, and it has some problems (for example, how do we handle the situation where a single post has two values for the same property) but the Cocoalicious project is all about experimentation, so I think I’m going to implement it anyway. Anybody have any interesting thoughts on the subject?
