Subject: Re: Certainty Factors Resent-Date: Mon, 13 Dec 1999 16:35:36 -0500 (EST) Resent-From: www-rdf-interest@w3.org Date: Mon, 13 Dec 1999 22:44:50 +0100 From: Jonas Liljegren To: Danny Ayers , RDF Intrest Group References: 1 Danny Ayers wrote: > > I'm just wondering what angle the proposed RDF spec takes for dealing > with uncertainty, and the 'truth' of a statement. The RDF does state that all statements is considered facts. It says that there can be a reification of a statement whithout the statment itself. This means that you can describe that someone states what they believe to be a fact, without yourself having to consider it a fact. You could in theory import a large body of statements from a foreign model, as reified statements only. You say that all these statements is the opinion of that particular source. You could, after your own reasoning, promote a select few of the statements to be facts even from your own perspective. In this sence, there is a binary state of trueness in the model. I have choosen to implement this as a bolean value coupled to every statement in my RDF database. I think that it would be good to have a common way to state the Certainty of a specific statement. And I think that it would still be practical to consider some things absolute facts. Given this, you could easily expand the system by asigning a Certainty to statements. But the statement would only be promoted to fact by the reasoning of the application. One of the application rules could be to promte statements with a Certainty of .95 or higher, there the Certainty statement belongs to the local model. The Certainty of a statement could be derived by the degree of trust for the origin of the model of the statement. exampel: A foreign model could set the Certainty for a statement to .50. Your general trust of the facts in models from that source could be .10. You could then add a new Certainty to the statement with the value of .05 and setting this to be a local statement. For every operation of the application, you would have to think about if you are intrested only in facts or also in probabilities. -- / Jonas - http://paranormal.o.se/perl/proj/rdf/schema_editor/