Are these RDFs the same thing?

I saved and generated these RDFs using the Jena API, and it came out as follows.

<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF 
xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#" 
xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
xml:base="urn:uuid:">

<rdfs:Class rdf:about="http://example.org/Animal"/>

<rdfs:Class rdf:about="http://example.org/Cat">
    <rdfs:subClassOf rdf:resource="http://example.org/Animal"/>
</rdfs:Class>

<rdfs:Class rdf:about="http://example.org/Dog">
    <rdfs:subClassOf rdf:resource="http://example.org/Animal"/>
</rdfs:Class>


</rdf:RDF>

Used Jena API and result

<rdf:RDF
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#">
  <rdfs:Class rdf:about="http://example.org/Dog">
    <rdfs:subClassOf>
      <rdfs:Class rdf:about="http://example.org/Animal"/>
    </rdfs:subClassOf>
  </rdfs:Class>
  <rdfs:Class rdf:about="http://example.org/Cat">
    <rdfs:subClassOf rdf:resource="http://example.org/Animal"/>
  </rdfs:Class>
</rdf:RDF>

I understand that rdf:resource can be rephrased as rdf:about. But why was rdfs:Classrdf:about="http://example.org/Animal"/ omitted?

Also, what is expressed as rdf:resource and what is expressed as rdf:about?

Solution

Yes, semantically, these two RDF/XML files serialize the same RDF. You can verify this for example by converting them to N-Triples, e.g. with Jena’s riot command-line tool:

riot --syntax=rdfxml --out=ntriples rdf.xml > rdf.nt

Both RDF/XML files will convert to (after sorting):

<http://example.org/Animal> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/01/rdf-schema#Class> .
<http://example.org/Cat> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/01/rdf-schema#Class> .
<http://example.org/Cat> <http://www.w3.org/2000/01/rdf-schema#subClassOf> <http://example.org/Animal> .
<http://example.org/Dog> <http://www.w3.org/1999/02/22-rdf-syntax-ns#type> <http://www.w3.org/2000/01/rdf-schema#Class> .
<http://example.org/Dog> <http://www.w3.org/2000/01/rdf-schema#subClassOf> <http://example.org/Animal> .

About RDF/XML

But why was <rdfs:Class rdf:about="http://example.org/Animal"/> omitted?

It exists in both files. In the second file, it’s nested in an <rdfs:subClassOf> element. RDF/XML allows for many such variations.

what is expressed as rdf:resource and what is expressed as rdf:about?

The rdf:resource attribute allows for a shorter representation, but can only be used in certain cases. See Empty Property Elements in the spec:

When a predicate arc in an RDF graph points to an object node which has no further predicate arcs, which appears in RDF/XML as an empty node element <rdf:Description rdf:about="..."> </rdf:Description> (or <rdf:Description rdf:about="..." />) this form can be shortened. This is done by using the IRI of the object node as the value of an XML attribute rdf:resource on the containing property element and making the property element empty.

NB: Unless you have to use RDF/XML, I would recommend using an RDF serialization like Turtle. It’s way easier to read/understand.