On 17/09/13 20:57, Claude Warren wrote:
public static void main(String ... argv) throws Exception
{
String[] lines = {
"<rdf:RDF",
" xmlns:rdf=\"http://www.w3.org/1999/02/22-rdf-syntax-ns#\";>",
" <rdf:Description rdf:about=\"e\">",
" <p5>verify base works</p5>",
" </rdf:Description>",
"</rdf:RDF>"
};
String eol = System.getProperty("line.separator");
StringBuilder sb = new StringBuilder();
for (String l : lines)
{
sb.append( l ).append(eol);
}
Model model = ModelFactory.createDefaultModel() ;
StringReader sr = new StringReader(sb.toString()) ;
model.read(sr, "http://example/";) ;
model.write(System.out, "N-TRIPLES") ;
System.out.println("-----") ;
model.setNsPrefix("ex", "http://example/";) ;
model.write(System.out, "RDF/XML-ABBREV", "http://another/";) ;
}
The above should create an RDF file that in TTL would be
[ <e> <p5> "verify base works" . ]
I would expect that the read could convert the <e> and <p5> to <
http://example/e> and <http://example/p5> respectively. However,
if you run the code you get
<http://example/e> <p5> "verify base works" .
and then an exception due to a relative URI in the output.
Should the <p5> be converted to <http://example/p5> either by the read or
<http://another/p5> by the write?
You have the information I have :-)
I looked at the RDF/XML spec and it seems to say that the URI resolution
rules that are specific to RDF apply to rdf:about and rdf:id. The rule
for XML tags looks like it is only XML namespaces and the RDF addition
for namespaces (concatenate namespace and local name; XML base does not
apply to namepaces in XML processing)
Andy
Claude
On Tue, Sep 17, 2013 at 10:10 AM, Andy Seaborne <[email protected]> wrote:
On 17/09/13 07:41, Claude Warren wrote:
So to summarize:
1) URIs in RDF inside jena are always absolute
"should be" rather than "must be" because there are ways round it but it
would not be proper RDF.
2) the "base" argument in a read provides the base to make relative URIs
absolute.
Yes - except NT where the format does not have a base concept and relative
URIs are illegal.
3) If the "base" on a read is not provided some reasonable value will be
constructed (e.g. file name) so there is no way to create an internal
representation of a relative URI through the read() methods.
Yes because there is always a base URI - the current directory.
This is not special to RDF - it comes from the URI RFC 3986, section 5.
4) the "base" argument in a write provides a mechanism to convert absolute
URIs to relative URIs in that URIs that have a namespace matching the base
are written as relative URIs
Yes (writer and syntax dependent)
5) if the "base" is not provided no conversion to relative URIs will be
performed.
Yes
Does that cover it?
Claude
Andy
