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Re: Proposed extensions to OWL?

From: Roger L. Costello <costello@mitre.org>
Date: Tue, 17 Jun 2003 20:31:14 -0500
Message-ID: <3EEFC0E2.2AED46D7@mitre.org>
To: www-rdf-interest@w3.org
CC: "Costello,Roger L." <costello@mitre.org>

Hi Folks,

Excellent discussions!  

I believe that it will be useful to delve into the meaning of
"equivalence".

Would someone please explain what this means:

   <owl:DatatypeProperty rdf:ID="length">
      <owl:equivalentProperty rdf:resource="#distance"/>
   </owl:DatatypeProperty>

What does it mean for an ontology to assert that "length is equivalent
to distance"?  How does this equivalence definition impact an
application processing instance documents which contain these
properties?

Suppose that one instance document contains this:

   <length>1 inch</length>

and a second instance document contains this:

   <distance>1 inch</distance>

What can an application conclude about the two elements?

Suppose that the instance documents contain these values:

   <length>1 inch</length>

and

   <distance>  1    inch  <distance>

What can an application conclude about the two elements?

What about these values:

   <length>1 inch</length>
   <distance>1.0 inch<distance>

Finally, what if the instance documents contain these values:

   <length>1 inch</length>
   <distance>2.54 centimeters<distance>

Does "equivalence" mean that:

(a) The "lexical values" in the instance documents must be identical? 
If so, then only these instances are equivalent:

   <length>1 inch</length>
   <distance>1 inch</distance>

or, does it mean that: 

(b) The "value space" must be identical?  If so, then all of the above
instances are equivalent (and it would be useful in the ontology to
clearly state the mathematical relationship between the two lexical
forms to show that the value space is identical).

If two properties are defined to be equivalent, then must they have the
same domain?  The same range?

Is it reasonable to define these two properties to be equivalent:

   {&metric;length, &english;length}

i.e., length in the metric system, and length in the English system.

To summarize: what does "equivalence" mean?  /Roger
Received on Tuesday, 17 June 2003 20:25:18 GMT

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