RE: relative uri references

Hello,

The main difficultly I see is that turning base off on a particular subset of the document might not be straightforward. You might
need to turn base off in case you really want to use relative Uris to identify entities. Now in XML, this is not difficult because
any element can contain xml:base; hence, you can always locally turn xml:base off by placing xml:base on the element with its value
equal to some opaque URI. To simulate that, we'd need to be able to enclose arbitrary subsets of the FS document into a local base
declaration. It is doable, but I wonder whether it is worth the trouble.

Note that in FS you can have a default namespace. Although this is not identical to xml:base (for example, this default namespace is
not affected by the physical URI of the document, and namespace expansion is by simply pasting the prefix rather than using URI
resolution algorithm), it achieves a similar goal as xml:base: you can write most of the URIs in the document without prefixing them
with any namespace.

Please let me know if you consider this insufficient.

Regards,

	Boris

> -----Original Message-----
> From: Ivan Herman [mailto:ivan@w3.org]
> Sent: 24 November 2008 11:49
> To: Boris Motik
> Cc: 'Alan Ruttenberg'; 'W3C OWL Working Group'
> Subject: Re: relative uri references
> 
> Boris,
> 
> did we ever consider adding a 'base', like 'xml:base', to the functional
> and the m'ter syntaxes?
> 
> Note that this is the only difference, for example, between the turtle
> specification as a team submission[1] and the earlier turtle
> specification: the former introduced a @base directive (alongside the
> @prefix ones). It might make sense to do this for the FS and M'Ter.
> 
> Just a thought
> 
> Ivan
> 
> 
> 
> [1] http://www.w3.org/TeamSubmission/turtle/
> 
> Boris Motik wrote:
> > Hello,
> >
> >
> >
> > In the RDF syntax, the resolution of URI references is governed fully by
> > the underlying RDF format. For example, if you are working with RDF/XML,
> > then the RDF parser should use xml:base. In addition, the XML parser
> > will expand any XML entities as well. There is no equivalent of the
> > Namespace declaration in the RDF syntax.
> >
> >
> >
> > In the XML Syntax, there are no Namespace declarations either. Again,
> > you have is xsd:base for relative URIs, and this is explicitly mentioned
> > in the document. Furthermore, we don't need a specific URI abbreviation
> > mechanism is because XML Syntax ontology documents can use XML entities
> > for abbreviation of long URIs.
> >
> >
> >
> > The functional-style syntax and the Manchester syntax, in contrast,
> > cannot rely on other specifications (such as RDF of XML) for
> > abbreviation and expansion of URI references, so they need their own URI
> > resolution mechanisms. In the functional-style syntax ontology
> > documents, only namespace declarations are expanded, and relative URIs
> > are not expanded. I think this is correct: we never say that the URIs of
> > ontology entities must be absolute. Thus, if someone actually creates
> > ontology entities with relative URIs, the functional-style syntax will
> > correctly capture this.
> >
> >
> >
> > Note that URIs have a well-defined identity. Therefore, a relative URI
> > provides a perfect way of identifying some ontology entity - that is, it
> > is a URI just like any other.
> >
> >
> >
> > Hence, it seems to me that we don't really need to say anything more
> > than what we've already said. We might only introduce additional
> > clarification into the XML Syntax document about relative URIs: we might
> > say that if you want to store such URIs, then you should explicitly turn
> > xml:base off on the element whether you are doing so; otherwise, your
> > relative URIs will accidentally be resolved against the xml:base and
> > that wopuld lead to problems. You can turn this resolution off by
> > placing on the element an xml:base with some opaque URI.
> >
> >
> >
> > Regards,
> >
> >
> >
> >             Boris
> >
> >
> >
> > ------------------------------------------------------------------------
> >
> > *From:* public-owl-wg-request@w3.org
> > [mailto:public-owl-wg-request@w3.org] *On Behalf Of *Alan Ruttenberg
> > *Sent:* 24 November 2008 06:05
> > *To:* W3C OWL Working Group
> > *Subject:* relative uri references
> >
> >
> >
> > Do we not  have to say how these are resolved in the functional and
> > manchester syntax, and might it not be best to explicitly say so for all
> > syntaxes?
> >
> >
> >
> > -Alan
> >
> 
> --
> 
> Ivan Herman, W3C Semantic Web Activity Lead
> Home: http://www.w3.org/People/Ivan/
> PGP Key: http://www.ivan-herman.net/pgpkey.html
> FOAF: http://www.ivan-herman.net/foaf.rdf

Received on Monday, 24 November 2008 12:07:34 UTC