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[DTB] Extractor function for the datatype? (was: [Fwd: Re: I18N issues an OWL2])

From: Axel Polleres <axel.polleres@deri.org>
Date: Thu, 10 Jul 2008 11:22:42 +0100
Message-ID: <4875E2F2.1000402@deri.org>
To: "Public-Rif-Wg (E-mail)" <public-rif-wg@w3.org>

For RIF only:

In the discussion arounf language-tags, I rtealized that something like 
SPARQL's datatype function [1] is missing in DTB.

Note however, that it is probably not so straight-forward to define...

func:datatype should return a datatype IRI for its argument.
THis is easy as long as we assume disjoint value spaces for all 
datatypes, but as soon as we talk about type hierarchies (subtypes)
things get messy, what should the function return in case?

the most specific or most generic type? I guess, we simply would need to 
defint it *per datatype* since this is not easy to answer.

I think basically, e.g. for the xsd/xdt built-in datatypes we adopt, we 
should rely on the XPath/XQuery typ hierarchy [2], and return the most 
specific type from that hierarchy. however, that would, for instance 
mean that, for

func:dataype("1.0"^^xs:decimal) you would get back

xs:integer

which may be considered awkward... opinions? Maybe this can be solved 
with a predicate instead of a function, similar to pred:iri-to-string, 
i.e. datatype-for-value(type, val)
which is true for type being the iri of any datatype in which value 
space val is.

Even if this isn't probabvly important for DTB's first WD, shall I add 
an editor's note that we discuss about whether some form of adoption of 
a function similar to sparql's datatype() would be feasible? Even if we 
don't add a note now, I would like to open this as an issue.

Opinions please!!!

Axel

1.http://www.w3.org/TR/rdf-sparql-query/#func-datatype
2.http://www.w3.org/TR/2004/WD-xpath-functions-20041029/#datatypes


-------- Original Message --------
Subject: Re: I18N issues an OWL2
Date: Thu, 10 Jul 2008 10:39:50 +0100
From: Axel Polleres <axel.polleres@deri.org>
Organization: DERI, National University of Ireland, Galway
To: Bijan Parsia <bparsia@cs.man.ac.uk>
CC: Phillips, Addison <addison@amazon.com>,  Dan Brickley 
<danbri@danbri.org>, Sandro Hawke <sandro@w3.org>, Jie Bao 
<baojie@cs.rpi.edu>,  OWL 1.1 <public-owl-wg@w3.org>, 
public-i18n-core-comments@w3.org <public-i18n-core@w3.org>, 
public-rif-comments@w3.org, public-webont-comments@w3.org
References: 
<4D25F22093241741BC1D0EEBC2DBB1DA013BB642BE@EX-SEA5-D.ant.amazon.com> 
<b6b357670807091132r5ac6f292paaefcc8702e9d4d2@mail.gmail.com> 
<4D25F22093241741BC1D0EEBC2DBB1DA013BB64C74@EX-SEA5-D.ant.amazon.com> 
<48753193.2020509@deri.org> <12918.1215647391@ubuhebe> 
<4D25F22093241741BC1D0EEBC2DBB1DA013BB6501A@EX-SEA5-D.ant.amazon.com> 
<274FC2EE-7C50-40BE-BAD1-379C85061831@cs.man.ac.uk>

Bijan Parsia wrote:
> (too many lists! :))
> 
> I'd like to raise a point that Dan Brickley (cced) often champions. If 
> it's more appropriate in a narrower scope, please narrow it for me!
> 
> In some applications, like FOAF, it's common to compare as equal two 
> strings with different language tags (esp. for such purposes as being a 
> database key like identifier). I can think of several ways to do this 
> (e.g., always comparing the strings and opting in to distinguishing the 
> languages), but I thought I'd raise the issue.
> 
> Cheers,
> Bijan.

Well, with the built-in functions in DTB [1]... you should be able to do
so, there are functions for extracting the string: by casting rif:text
to xs:string [2]) as well as extracting the lang-tag (by adopting
SPARQL's lang function [3]. Note that the former would be even easier
with the langtag-as-dataype proposal, and for the latter, we'd need a
function which returns the datatype of a literal... we have to discuss
this, since sparql's datatype function [4] is not straightforwardly
applicable to RIF semantically... at least there are some implications
in defining it, I guess.

Axel

1.http://www.w3.org/2005/rules/wiki/DTB
2.http://www.w3.org/2005/rules/wiki/DTB#xs:string
3.http://www.w3.org/2005/rules/wiki/DTB#func:lang_.28adapted_from_SPARQL.27s_lang_function.29
4.http://www.w3.org/TR/rdf-sparql-query/#func-datatype

-- 
Dr. Axel Polleres, Digital Enterprise Research Institute (DERI)
email: axel.polleres@deri.org  url: http://www.polleres.net/

Everything is possible:
rdfs:subClassOf rdfs:subPropertyOf rdfs:Resource.
rdfs:subClassOf rdfs:subPropertyOf rdfs:subPropertyOf.
rdf:type rdfs:subPropertyOf rdfs:subClassOf.
rdfs:subClassOf rdf:type owl:SymmetricProperty.


-- 
Dr. Axel Polleres, Digital Enterprise Research Institute (DERI)
email: axel.polleres@deri.org  url: http://www.polleres.net/

Everything is possible:
rdfs:subClassOf rdfs:subPropertyOf rdfs:Resource.
rdfs:subClassOf rdfs:subPropertyOf rdfs:subPropertyOf.
rdf:type rdfs:subPropertyOf rdfs:subClassOf.
rdfs:subClassOf rdf:type owl:SymmetricProperty.
Received on Thursday, 10 July 2008 10:23:26 GMT

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