Defining Properties

<rdf:Property rdf:ID="IsAnchor">

  <rdfs:domain rdf:resource="#SvgEntity"/>

  <rdfs:range rdf:resource="#boolean"/>

</rdf:Property>

<rdf:Property rdf:ID="Labelled">

  <rdfs:domain rdf:resource="#SvgEntity"/>

  <rdfs:range rdf:resource="#boolean"/>

</rdf:Property>

<rdf:Property rdf:ID="LabelledBy">

  <rdfs:subPropertyOf rdf:resource="#Labelled"/>

  <rdfs:range rdf:resource="#SvgEntity"/>

</rdf:Property>

And here is the full (RDF) schema...