Can I use namespace prefix in rdf:about attribute?

Question

Am I supposed to be able to use a namespace prefix when referring to a subject with the "rdf:about" attribute in RDF/XML, like so:

<rdf:RDF xmlns:myns="http://example.org/someBaseURI#">
<rdf:Description rdf:about="myns:someEntity">
...

I can't find any such example on the net, and the RDF library I'm using (ARC2) doesn't seem to support it, so I wanted to make clear whether it is supposed to work or not according to standards.

Accepted Answer

No you can't: According to the Relax NG the rdf:about statement requires an URI reference:

aboutAttr = 
  attribute rdf:about { 
    URI-reference 
}

A RDF URI reference is defined as follows:

6.4 RDF URI References

A URI reference within an RDF graph (an RDF URI reference) is a Unicode string that:

• does not contain any control characters ( #x00 - #x1F, #x7F-#x9F)
• and would produce a valid URI character sequence (per RFC2396 [URI], sections 2.1) representing an absolute URI with optional fragment identifier when subjected to the encoding described below.

http://www.w3.org/TR/2004/REC-rdf-concepts-20040210/#dfn-URI-reference

Answer 2

2	No you can't. This is one of the many reasons why Turtle is so much better than RDF/XML. link answered 11 Jul '10, 00:59 cygri ♦ 8.8k●4●12 accept rate: 34%

Answer 3

It seems like it does not work in practice, either. Given the xml input

  <?xml version="1.0"?>
  <rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
           xmlns:myns="http://example.org/someBaseURI#">
    <rdf:Description rdf:about="myns:someEntity">
       <myns:someProperty>foo</myns:someProperty>
    </rdf:Description>
  </rdf:RDF>

The W3C's validator doesn't complain, but produces a triple with the subject prefix not expanded.

  myns:someEntity http://example.org/someBaseURI#someProperty "foo" .

Running it through cwm produces similar results.

  ~> cwm --rdf test.xml --ntriples
  <myns:someEntity> <http://example.org/someBaseURI#someProperty> "foo" .

Answer 4

As others have said, no you can't. You can, however, define the prefix as an XML entity at the head of the file, so that you only have one place to keep prefixes up-to-date. The principle problem with this approach (other than the ugly XML entity syntax) is that few, if any, RDF tools that I can think of will preserve XML entity declarations between reading and subsequent writing. So it works OK on files that you directly edit yourself in a text editor or XML editor, but not otherwise.

Having said that, I'd agree with Richard that using Turtle as your input syntax is a better idea. If you need XML as part of your toolchain, there are tools that can convert Turtle to XML.