Why doesn't FOAFFriends.rdf have a xml:base declaration?

[ab...@thomsonreuters.com]

Hi,

 

    I am a beginner for Semantic Web and currently working with JENA. I
came across the attached file FOAFFriends.rdf that could be read into a
Model with the following statement:

 

private void populateFOAFFriends(){

            _friends = ModelFactory.createOntologyModel();

            InputStream inFoafInstance =
FileManager.get().open("Ontologies/FOAFFriends.rdf");

            _friends.read(inFoafInstance,defaultNameSpace);

}

 

Also, here the defaultNameSpace is: 

 

static String defaultNameSpace = 
http://semwebprogramming.org/2009/ont/chp2#

 

I have the following question:

The attached file has declarations such as rdf:ID="me". I believe from
my reading that if there is rdf:ID declaration in a RDF document, then
it should also contain xml:base declaration, but the file is missing
this declaration. So, how is JENA successfully able to read the RDF
file? Where does it get the xml:base declaration from to determine the
complete URI of "me"? Does it do something with the defaultnamespace? 

 

If you say defaultnamespace to be the xml:base, then my question would
be that the xml:base should not contain the # symbol at the end but the
declaration here for defaultnamespace does. How do you justify this
please?

 

A quick reply would be highly appreciated.=

 

Thanks

With Regards,

Abhishek S


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Re: Why doesn't FOAFFriends.rdf have a xml:base declaration?

[Andy Seaborne <an...@epimorphics.com>]

On 07/07/11 08:27, abhishek.shivkumar@thomsonreuters.com wrote:
> Hi,
>
> I am a beginner for Semantic Web and currently working with JENA. I came
> across the attached file FOAFFriends.rdf that could be read into a Model
> with the following statement:
>
> *private**void*populateFOAFFriends(){
>
> _friends= ModelFactory./createOntologyModel/();
>
> InputStream inFoafInstance =
> FileManager./get/().open("Ontologies/FOAFFriends.rdf");
>
> _friends.read(inFoafInstance,/defaultNameSpace/);

it's not the default namespace - it's the base URI.  The base comes from

1/ xmlbase declaration (nestable)
2/ The declared one
3/ where it's read from if appropriate and meaningful.

See RFC 3986 section 5.

Any relative URI wil be resolved against the base URI as part of parsing.

>
> }
>
> Also, here the defaultNameSpace is:
>
> *static*String /defaultNameSpace/=
> http://semwebprogramming.org/2009/ont/chp2#
>
> I have the following question:
>
> The attached file has declarations such as rdf:ID=”me”. I believe from
> my reading that if there is rdf:ID declaration in a RDF document, then
> it should also contain xml:base declaration, but the file is missing
> this declaration. So, how is JENA successfully able to read the RDF
> file?

The base URI is provided externally to

  Model 	read(InputStream in, String base)


> Where does it get the xml:base declaration from to determine the
> complete URI of “me”? Does it do something with the defaultnamespace?
>
> If you say defaultnamespace to be the xml:base, then my question would
> be that the xml:base should not contain the # symbol at the end but the
> declaration here for defaultnamespace does. How do you justify this please?

Justify?

It's part of the standard process for URI resolution (RFC 3986).

http://semwebprogramming.org/2009/ont/chp2#

if in HTML you had <a href="foo"> you'd expect

http://semwebprogramming.org/2009/ont/foo
right?

if in HTML you had <a href="#bar"> you'd expect
http://semwebprogramming.org/2009/ont/chp2#bar

It's not a simple concatenate.

rdf:ID="me" => a relative URI of #me because it's defined to be that:

http://www.w3.org/TR/rdf-syntax-grammar/#section-Syntax-ID-xml-base

Resolve "#me" with base http://semwebprogramming.org/2009/ont/chp2# and 
you get

http://semwebprogramming.org/2009/ont/chp2#me

(there's no double #).

>
> A quick reply would be highly appreciated.=
>
> Thanks
>
> With Regards,
>
> Abhishek S
>
>
> This email was sent to you by Thomson Reuters, the global news and
> information company. Any views expressed in this message are those of
> the individual sender, except where the sender specifically states them
> to be the views of Thomson Reuters.