From: Roger L. Costello <costello@mitre.org>

Date: Sun, 15 Jun 2003 07:00:45 -0400

Message-ID: <3EEC51DD.D64D5960@mitre.org>

To: www-rdf-interest@w3.org

CC: robin.berjon@expway.fr, "Costello,Roger L." <costello@mitre.org>

Date: Sun, 15 Jun 2003 07:00:45 -0400

Message-ID: <3EEC51DD.D64D5960@mitre.org>

To: www-rdf-interest@w3.org

CC: robin.berjon@expway.fr, "Costello,Roger L." <costello@mitre.org>

Hi Folks, The more that I think about this problem, the more convinced I am that adding something like a conversionFactor attribute is the right way to go, e.g., <owl:DatatypeProperty rdf:ID="length-in"> <owl:equivalentProperty rdf:resource="#length-cm" owl-x:conversionFactor="length-in/value() = length-cm/value() / 2.54"/> <rdfs:range rdf:resourse="&xsd;decimal"/> </owl:DatatypeProperty> Let me explain. Consider the meaning of this: <owl:DatatypeProperty rdf:ID="a"> <owl:equivalentProperty rdf:resource="#b"/> </owl:DatatypeProperty> It says that "a and b represent the same type of thing (they are equivalent), with a conversionFactor of 'equality'". That is, implicitly, the definition is stating this: <owl:DatatypeProperty rdf:ID="a"> <owl:equivalentProperty rdf:resource="#b" owl-x:conversionFactor="a/value() = b/value()"/> </owl:DatatypeProperty> "Given an instance of a and an instance of b, they can be considered equivalent *provided* the value of 'a' equals the value of 'b'." Thus, <owl:DatatypeProperty rdf:ID="length-in"> <owl:equivalentProperty rdf:resource="#length-cm" owl-x:conversionFactor="length-in/value() = length-cm/value() / 2.54"/> <rdfs:range rdf:resourse="&xsd;decimal"/> </owl:DatatypeProperty> "Given an instance of length-in and an instance of length-cm, they can be considered equivalent *provided* the value of length-in equals the value of length-cm / 2.54" In other words, a "conversionFactor" is implicit in this definition: <owl:DatatypeProperty rdf:ID="a"> <owl:equivalentProperty rdf:resource="#b"/> </owl:DatatypeProperty> I propose that we make the "conversionFactor" explicit, so that more sophisticated mathematical relationships can be expressed. Also, I propose that xPath be leveraged to express the relationships. Comments? /Roger P.S. I looked at RuleML and feel that it is not appropriate for this problem. RuleML gives a way to state inferences. In this problem, I am not trying to state an inference. I am merely trying to assert equivalence (by a conversion factor). "Roger L. Costello" wrote: > > Hi Folks, > > Yesterday I sent out a message asking about technologies to express > mathematical relationships. Robin Berjon responded with a very > interesting idea. I would like to get your thoughts on it, and see if > collectively we can come up with something cool. > > First I will show you a slightly modified version of Robin's proposal, > then I will show Robin's original proposal. > > Robin's Idea Slightly Modified > > The idea is to extend OWL and base the solution on xPath. > > Suppose that I would like to state that these two properties are > equivalent via a conversion factor: > > length-in, length-cm > > i.e., length in inches, and length in centimeters > > The conversion factor is: > > length-in = length-cm / 2.54 > length-cm = length-in * 2.54 > > With today's OWL here is how you would define these properties: > > <owl:DatatypeProperty rdf:ID="length-in"> > <rdfs:range rdf:resourse="&xsd;decimal"/> > </owl:DatatypeProperty> > > <owl:DatatypeProperty rdf:ID="length-cm"> > <rdfs:range rdf:resourse="&xsd;decimal"/> > </owl:DatatypeProperty> > > The proposal is to extend OWL to allow you to assert that these two > properties are equivalent by the above conversion factor. Here's how it > might look: > > <owl:DatatypeProperty rdf:ID="length-in"> > <owl:equivalentProperty rdf:resource="#length-cm" > owl-x:conversionFactor="current() * 2.54"/> > <rdfs:range rdf:resourse="&xsd;decimal"/> > </owl:DatatypeProperty> > > <owl:DatatypeProperty rdf:ID="length-cm"> > <owl:equivalentProperty rdf:resource="#length-in" > owl-x:conversionFactor="current() / 2.54"/> > <rdfs:range rdf:resourse="&xsd;decimal"/> > </owl:DatatypeProperty> > > where: > owl-x is an OWL eXtension namespace, > current() is the xPath function referring to the current node. > > Now let me show you Robin's idea: > > Robin's idea is also to base the solution on xPath. Here's what Robin > said: > > "For instance: > > <foo:PropertyEquivalence from='measure:inch' > to='measure:cm' > convert='$in_1 * 2.54'/> > > <foo:PropertyEquivalence from='measure:cm' > to='measure:in' > convert='$in_1 div 2.54'/> > > would allow you to declare that the following are equivalent: > > <geo:Distance> > <measure:inch>2</measure:inch> > </geo:Distance> > > <geo:Distance> > <measure:cm>5.08</measure:cm> > </geo:Distance> > > You could allow for multiple inputs to your binding: > > <foo:PropertyEquivalence > from='size:width/measure:meter > size:length/measure:meter' > to='size:surface/measure:squareMeter' > convert='$in_1 * $in_2'/> > > and perhaps equivalentize, depending on whether it makes sense in that > context: > > <flat:Bedroom> > <size:width><measure:meter>4</measure:meter></size:width> > <size:length><measure:meter>5</measure:meter></size:length> > </flat:Bedroom> > > <flat:Bedroom> > <size:surface> > <measure:squareMeter>20</measure:squareMeter> > </size:surface> > </flat:Bedroom> > > so that given the first you could still query for flat:Bedrooms that > are larger than 20sqm. > > You may need to throw in stuff from EXSLT Math if you want more than > XPath provides." > > .... > > Okay, those are the two ideas thus far. What do you think? Feel free > to add your own ideas. If this whole approach is bad, feel free to say > so. The intent here is to brainstorm. If these conversion rules are > better stated using another technology (e.g., RuleML) please say so. > /RogerReceived on Sunday, 15 June 2003 07:02:24 UTC

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