- From: Dan Brickley <danbri@w3.org>
- Date: Wed, 29 Sep 2004 14:41:24 -0400
- To: Stella Dextre Clarke <sdclarke@lukehouse.demon.co.uk>
- Cc: public-esw-thes@w3.org, "'Miles, AJ (Alistair) '" <A.J.Miles@rl.ac.uk>
Hi Stella, * Stella Dextre Clarke <sdclarke@lukehouse.demon.co.uk> [2004-09-29 18:20+0100] > > Sorry, but I am completely lost in this conversation. Seems to me what > this bloke Alistair J Miles is really looking for is a sort of "Beam me > up Scotty" over the Internet. (Any minute now he'll pop right out of my > monitor.) I'm not just making a joke of it. I think I am saying you are > asking for the moon, and any approximation to the moon could prove > unsatisfactory. It's a tricky idea to explain, but I've seen enough RDF applications that describe people and other entities directly that I know it's not a moon-on-stick. So I think the problem is with communicating the basic idea (Sorry!). Let me try to redescribe the issue... SKOS uses W3C's Resource Description Framework (RDF) to describe thesauri (and similar things). Other projects (eg. FOAF, RSS, MusicBrainz, rdf-calendar) use RDF to describe various other kinds of things, such as people, news item syndication, music, albums, artists, calendars. Sometimes thesauri cover, to some extent, areas which are also covered by other RDF-based projects. We are looking for ways to make this explicit, so that simple-minded machines can query their database and find matches, regardless of whether a thesaurus-based approach or a plain-RDF approach was used. RDF (and OWL) are at their best when modelling things in terms of individuals which have properties/attributes and which fall into classes/categories. Lots of the world can be modelled in terms of things and categories and properties in this way, which is why RDF appeals. But RDF's perspective on the world doesn't work so well "out of the box" when trying to model things like fluids / mass nouns, or processes. So there are often enough concepts in a thesaurus that don't have an obvious correlation in non-SKOS RDF descriptions. That's OK. It's one of the reasons that SKOS is important. But the concern here is with the overlap areas, with things (typically individuals/objects, or classes of individual/object) which are (i) picked out in the SKOS world by being the basis for 1 or more SKOS concepts (ii) likely also to be described using various other RDF-based formats. RDF tries to impose some basic design constraints across all projects that use it, to make things easier for data-merging, extensibility etc. What we're doing with skos:represents (or whatever it gets called) is coming up with a little add-on that helps SKOS-based RDF data work better with non-SKOS RDF data. For cases like people, places, organisations, this is quite important, since non-SKOS RDF can directly model some very detailed characteristics of these entities. We can use non-SKOS RDF to describe a Person's age, height, employer, etc.; or a place's latitute and longitude, or an Organization's certifications. That's the sort of task RDF was built for. But at the same time we can use SKOS RDF to describe thesauri which mention those self-same people, places, organizations, and which treat them explicitly as concepts in a knowledge organization system. Often these thesauri are used in bibliographic datasets, library practice etc., and so can be hugely useful for information retrieval purposes. The moon on the stick that we're chasing after is to be able to combine both styles of representation. So for example we might draw upon a SKOS/RDF thesaurus that included concepts corresponding to various organisations (eg. UN, CND, Fox Hunters Anonymous etc). And we might draw upon some non-SKOS RDF to learn more about those organizations, for eg. that the UN is xyz:headQuarteredIn New York, or was xyz:formed_in "1942" (or whenever...). SKOS is great at hooking into established thesauri, and at representing those aspects of the world that aren't so easy to describe in terms of individuals, classes and properties. Non-RDF SKOS is better than SKOS at describing arbitrary named properties of individual things, and the class hierarchies they can be categorised into. Both are useful and valuable, and the use of RDF means the two can be used alongside each other. What I'm hoping for is that we can go a little further than simply using these approaches in parallel, and start to figure out how to build little bridges between these complementary styles of representation... I suspect the reason that this is confusing (apart from my own limitations at explaining things) is that RDF is simultaneously (i) a (friendly!) "rival" to the thesaurus-based approach to describing/classifying/etc (ii) a platform within which thesauri can be represented pretty much as-is, without having to reorganise them to fit with RDF's own representational conventions. In other words, when people ask us "Should I be creating an Ontology or a Thesaurus?", we want to figure out what to tell them (beyond "yes!") about the diffent approaches possible using SKOS, RDF, OWL etc. And hopefully have some conventions for connecting up information created in either style. verbosely, Dan
Received on Wednesday, 29 September 2004 18:41:24 UTC