Re: added diagrams to "Using XML Schema Data Types..."

From: Peter F. Patel-Schneider (
Date: 02/07/01

From: Jim Hendler <>
Subject: Re: added diagrams to "Using XML Schema Data Types..."
Date: Wed, 7 Feb 2001 13:57:26 -0500

> At 12:40 PM -0600 2/7/01, Dan Connolly wrote:
> >
> >
> >To have the parsing of one document depend on the
> >contents of another conflicts with that goal/principle.
> >
> >Another way to state this principle is that
> >the knowledge contained in two documents, X and Y,
> >is always the conjunction of the knowledge in X with
> >the knowledge in Y. To allow X to change what Y says
> >in some non-monotonic way doesn't seem scalable/workable
> >to me.
> >
> I absolutely agree with the first of these and completely disagree 
> with the second, so maybe they're not exactly equivalent... since I 
> tend to like examples, here's one
> Web page 1 says:  X is true
> Web page 2 says:  X is False
> The parsing of web page 1 or two is not changed by reading the other, 
> but I don't know a good monotonic way to combine these two without 
> problem (solution is for me to tag them, or reject them, or something 
> - but I need to be allowed to recognize conflict)
> web page 1 says: 1 is an integer
> web page 2 says: 1 is a real
> web page 3 says: 1 is not an integer
> are these cases inherentely different?  I'm not sure,
> Prof. James Hendler
> Computer Science Dept		703-696-2238 (phone)
> Univ of Maryland		703-696-2201 (Fax)
> College Park, MD 20853

The *monotonic* way of combining these two sources is to be(come)
inconsistent.  This is perfectely fine logically, but probably not exactly
what is wanted in a pragmatic sense.  A better solution is to back out of
the committment to one or the other, using some extra-logical information.
As information has been removed in this process, there is no requirement of


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