- From: Jonathan Borden <jonathan@openhealth.org>
- Date: Fri, 31 May 2002 08:08:46 -0400
- To: <www-rdf-logic@w3.org>
- Cc: "R.V. Guha" <guha@guha.com>, "pat hayes" <phayes@ai.uwf.edu>
R.V.Guha wrote: [[ Jonathan, We were imprecise in our language. Sorry. We should have said that dark triples introduce non-mon into the rest of any language whose semantics interprets them. DTs themselves are monotonic. As to your example, the issue is that the semantics of some language (in this case OWL), would need to incorporate a check for formulae involving the color of terms in the formulae wherein the color itself was expressed using other formulae. This is what causes the non-mon. My intuition is that the formulae stating darkness are coming near the realm of (but not close enough to cause paradoxes) stating things about the semantics of the language that we are seeing non-mon. Any closer or any more powerful constructs and we will be there. ]] -- http://lists.w3.org/Archives/Public/www-rdf-logic/2002May/0120.html It seems that RDF on the web is inherently colored, and hence I don't see DT introducing more problems that might already exists. I say this because the "lightness" of any graph of triples is dependent on the viewing of the graph with respect to the _current_ graph. That is, any URIrefs within the current graph which identify _another_ RDF graph, do not take as asserted the statements within _that_ graph. Simplifying the situation to remove factors involving protocols and networks (if we don't make some simplifying assumptions this gets horribly complicated) let us assume that rather than the color of any 'ol RDF document being "rdf:White" by assumption, instead, let us color the RDF graph by the _base URI_ of the originating document. Now we can express the _current document_ as a URI, and under base RDF (i.e. every triple asserted), the set of asserted triples is the set of triples whose _color_ is equal to the _current document_ i.e. the _base URI_. Now the process of "merging" graphs can be represented by the recoloration of one graph either to match the second graph, or else the assignment of a new color to both graphs (thankfully there is no limit to the number of URIs we may use :-) As an implementation, a 'triple' store would be able to suck in every RDF document it pleases and store them alongside eachother (colored triples) and yet keep track of what is asserted with respect to each document and what isn't. This process would seem entirely monotonic to me, assuming we agree on a unique base URI for each document ... and the web does assume this base URI. So already, RDF seems entirely colored from a practical perspective. Any 'RDF inferencing engine' whatever that may be _already_ has to decide what is a truth and what isn't (or at the very least what is an assertion), even if only to say "I accept as asserted all triples whose color is the current base URI." Now suppose all the triples in a 'document' aren't assigned the same color, i.e. some aren't colored to the base URI, so what? I don't see how this process of coloring _intrinsicly_ adds any non-monotonicity above what would already exist. I submit that my way of viewing the RDF world is entirely consistent and that allowing triples to be syntactically colored is just as monotonic -- perhaps more! -- than coloring by virtue of an originating base URI. Jonathan
Received on Friday, 31 May 2002 08:17:35 UTC