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Re: DAML: restricting number of elements in a list

From: Andrei S. Lopatenko <andrei@derpi.tuwien.ac.at>
Date: Mon, 11 Feb 2002 10:14:30 +0100
Message-ID: <005201c1b2dc$830dbf30$a6498280@tuwien.ac.at>
To: "Ian Horrocks" <horrocks@cs.man.ac.uk>, "Steven Gollery" <sgollery@cadrc.calpoly.edu>
Cc: <www-rdf-logic@w3.org>

Would it be a right way
   create class
VertexInPoligon  subClassOf Vertex
with   property connectsTo   - range VertexInPoligon
So we can create an ordered list of Vertexes
Then class Polygon also has property connectsTo which points to the first
vertex in ordered list of vertexes for polygon
Property connectsTo must be transitive
And for class Polygon mincardinality of connectsTo is three.
So an ORDERED list of vertexes is supported and cardinality is supported as
well

The only problem in such schema one VertexInPoligon can connects to a few
other Vertexes. Due to transitivety of property it would be wrong to say
maxcardinality connectsTo is one for VertexInPoligon
As far as I understand due to transitivity of connectsTo it is imposible to
request to which VertexInPolygon Polygon connects first. But taking all
Vertexes of given polynom and relation connectsTo between them such order
can be easily reconstructed assuming that there no cycles and wrong
assertation which are not really prohibit in this schema


<daml:Class rdf:ID="VertexInPolygon">
    <rdfs:subClassOf rdf:resource="#Vertex">
</daml:Class>

<daml:TransitiveProperty rdf:ID="connectsTo">
    <rdfs:Range rdf:Resource="#VertexInPolygon"/>
    <rdfs:Domain>
        <daml:unionOf>
            <daml:Class rdf:about="VertexInPolygon"/>
            <daml:Class rdf:about="Polygon"/>
        </daml:unionOf>
    </rdfs:Domain>
</daml:TransitiveProperty>

<daml:Class rdf:ID="Polygon">
  <rdfs:subClassOf>
    <daml:Restriction daml:minCardinality="3">
      <daml:onProperty rdf:resource="connectsTo"/>
    </daml:Restriction>
  </rdfs:subClassOf>
 </daml:Class>


Best regards
MSc Andrei S. Lopatenko
Researcher
Vienna University of Technology
A chairman of CERIF Task Group
euroCRIS conc.
http://purl.org/NET/andrei


----- Original Message -----
From: "Ian Horrocks" <horrocks@cs.man.ac.uk>
To: "Steven Gollery" <sgollery@cadrc.calpoly.edu>
Cc: <www-rdf-logic@w3.org>
Sent: Saturday, February 09, 2002 6:36 PM
Subject: Re: DAML: restricting number of elements in a list


> On February 6, Steven Gollery writes:
> > I'm working on an ontology in DAML that includes some geometric
> > concepts. I would like to be able to somehow define a property Vertices
> > whose domain is the Polygon class and whose range is ordered collections
> > of instances of the Point class, where the length of the ordered
> > collection is at least three.
> >
> > It would be fairly straightforward to say that each Polygon must have at
> > least three values of a Vertex property which is restricted to class
> > Point, but that would lose the idea the vertices have an order -- the
> > order is obviously a fundamental part of the semantics for the polygon.
> >
> > Does DAML provide any way to restrict the number of elements in a list?
> > Or is there some other way to do what I need here?
>
> There is no language construct that supports this - properties of a
> DAML class are always unordered. One possible solution is to make the
> range of Vertex a more complex structure that describes both the point
> and its place in the list. This is not completely satisfactory as it
> is difficult to ensure that the list values are sensibly ordered.
>
> Another solution is to define subproperties of Vertex called Vertex1,
> Vertex2 etc., each being a unique property (i.e., functional). The
> main disadvantage with this method is that the maximum number of
> vertices must be decided a priori. Ensuring that values are sensibly
> ordered is a little easier in this case because the functionality
> already precludes the case where there is more than one vertex with
> the same number. Simply asserting, for each n from 2 to the max vertex
> number, that the existence of the property Vertexn implies the
> existence of the property Vertexn-1 should be enough to ensure that
> there are no "gaps" in the list of vertices.
>
> Hope this helps.
>
> Ian Horrocks
>
> >
> > Thanks in advance,
> >
> > Steve Gollery
> > sgollery@cadrc.calpoly.edu
> >
> >
>
>
Received on Monday, 11 February 2002 04:58:04 GMT

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