After a rather interesting day of discussion at HP Labs on Friday it occured to me that RDF has a memory like a goldfish. Everything asserted in RDF is asserted now, there’s no future, no past to RDF, only the present. I’m not explaining this very well. I mean that if I was an RDF datasource, I wouldn’t know anything about the past or the future. hmm, ‘if I were an RDF datasource’…maybe I’ve been doing this a bit too long 😉
Anyway, this means that change is tricky to represent, for example, vocabularies changing over time. Interesting because one of the themes of the day was that RDF can help in explaining what people actually meant when they wrote, say, an XML schema, or iCalendar. Ploughing through the iCalendar RFC 2445 to translate it to RDF was so hard because the written descriptions were ambiguous. One of the issues is the lack of documentation about the reasons decisions were made. This is part of the documentation of a vocabulary (and of course a very good reason for an open process, where the decisions can be tracked somewhere, e.g. on a mailing list). I’m trying to document RDF ical, by summaraising the available public information in one place.
RDF cannot of itself provide dated tracking information of this kind; though I think Topicmaps can. Applications can provide this information of course, either through modelling (for example using events as first class objects, as Dan et al designed in the Harmony project) or outside the RDF model, via tracking the source or provenance, as scutters have to do.