RDF Question: about syntax of rdf container objects (Bag, Alt, Seq)
Roger L. Costello
costello at mitre.org
Thu Apr 8 12:28:18 BST 1999
In section 3 of the RDF Model & Syntax spec it talks about containers,
e.g., rdf:Bag, rdf:Alt, and rdf:Seq. It gives an example where the
model and syntax is shown for the following statement:
"The students in course 6.001 are Amy, Tim, John, Mary, and Sue."
The model for this statement shows a resource, /courses/6.001, having a
property, students, whose value is an anonymous resource (i.e., a
resource with no identifier). The anonymous resource has an rdf:type
property whose value is rdf:Bag. It has a property rdf:_1 whose value
is /Students/Amy. It has a property rdf:_2 whose value is
/Students/Tim, etc.
The spec shows the syntax for this model as:
<rdf:RDF>
<rdf:Description about="http://mycollege.edu/courses/6.001">
<s:students>
<rdf:Bag>
<rdf:li resource="http://mycollege.edu/students/Amy"/>
<rdf:li resource="http://mycollege.edu/students/Tim"/>
<rdf:li resource="http://mycollege.edu/students/John"/>
<rdf:li resource="http://mycollege.edu/students/Mary"/>
<rdf:li resource="http://mycollege.edu/students/Sue"/>
</rdf:Bag>
</s:students>
</rdf:Description>
</rdf:RDF>
This confuses me. It does not seem to faithfully represent the model.
Recall that the model says that resource, /courses/6.001, has a
property, students, whose value is an *anonymous resource*. This syntax
does not seem to be expressing that. This syntax says that the value is
an rdf:Bag, not an anonymous resource. Here's how I would write the
syntax:
<rdf:RDF>
<rdf:Description about="http://mycollege.edu/courses/6.001">
<s:students>
<rdf:Description>
<rdf:type resource="rdf:Bag"/>
<rdf:li resource="http://mycollege.edu/students/Amy"/>
<rdf:li resource="http://mycollege.edu/students/Tim"/>
<rdf:li resource="http://mycollege.edu/students/John"/>
<rdf:li resource="http://mycollege.edu/students/Mary"/>
<rdf:li resource="http://mycollege.edu/students/Sue"/>
</rdf:Bag>
</s:students>
</rdf:Description>
</rdf:RDF>
The way I read my version, the resource, /courses/6.001, has a property,
students, whose value is an anonymous resource. The anonymous resource
has a type property whose value is rdf:Bag, and so on. Isn't this a
more faithful representation of the model? I must be not understanding
something about container objects. Would someone please explain this to
me? /Roger
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