Re: DAML+OIL Query Language and RQL

From: Peter F. Patel-Schneider (
Date: 09/25/01

From: Richard Fikes <>
Subject: DAML+OIL Query Language and RQL
Date: Mon, 24 Sep 2001 11:05:55 -0700

> The text at the beginning of my initial message on DQL 0.1 was intended
> to be an informal description of the language.  I don't think I can do
> much better than that and so will include it again here:
> -----------------------------------
> An instance of class Query represents a question posed to a reasoner.  A
> query instance consists of two parts: a query premise and a query
> pattern.  A query premise is a DAML+OIL KB that is effectively asserted
> to the queried KB for the duration of the query.  It is to contain
> assumptions particular to the current query.  The query premise can be
> empty to indicate the absence of such assumptions.  A query pattern is
> the question itself.  It is in effect a conjunction of one or more
> triples.  Each triple corresponds to an RDF Statement except that its
> predicate, subject, and/or object can be a variable.  Variables present
> in a query pattern, if any, are implicitly quantified existentially at
> the beginning of the pattern.  Syntactically, a query pattern is in xml
> markup.
> An answer to a query specifies an instance of the query pattern all of
> those RDF statements are entailed by the KB being queried conjoined with
> the query premise KB.  An instance of class QueryAnswer represents one
> answer to a query.  A query answer instance consists of two principle
> parts: the query posed and a set of bindings to the query variables
> representing an instantiation of those query variables.

I would like to see a more-formal description of DQL in the near future.
In particular, I would like to see a formal definition of what an answer
is.  (For example, what if there are two resources that are defined as
being the same.  Do these constitute one answer or two?)


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