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a few comments about DTB

From: Jos de Bruijn <debruijn@inf.unibz.it>
Date: Fri, 30 May 2008 13:39:47 +0200
Message-ID: <483FE783.3020903@inf.unibz.it>
To: Axel Polleres <axel@polleres.net>
CC: RIF WG <public-rif-wg@w3.org>

Axel,

Here are a few things I noticed in the DTB document during the meeting:

- you use DATATYPE sometimes as the IRI of a datatype and sometimes as a 
non-IRI name of a datatype.  It is unclear what the relationship is 
between these two names, especially since according to section 2.2 the 
names of the data types are IRIs.  In addition, the names are not always 
what one would expect.  For example, I would expect the short name of 
the xs:string datatype to be "string".  However, in section 4.1 and 4.2 
it seems to be "String".
I guess it probably makes sense to use some kind of short names for the 
datatypes in the names of certain predicates, but the relationship needs 
to be defined.
- section 4.1, first sentence: as discussed in the meeting, it is 
unclear what is meant with "RIF supporting a datatype".  As agreed in 
the meeting, a dialect may require implementations to support a specific 
datatype.  The DTB document then only needs to specify that whenever a 
datatype is supported, also the corresponding (which is a concept also 
to be defined here) positive and negative guards must be supported.
If you do not support guards for a particular datatype, then arguably 
you do not support the datatype, so I think that's a reasonable 
requirement.  It is also necessary, for example, for embedding RIF-RDF 
combinations into RIF.
- section 4.3, casting:
The casting functions are under-defined:  1 It is unclear for which data 
types these functions are defined.
2 the reference to the table in section 17.1 seems to be incorrect.  The 
table does not specify any conversions.  It actually specifies which 
cast functions are defined, not how they are defined.  You can probably 
use the table for defining which cast functions exist.
Then, the table only speaks about XML schema datatypes, which seems 
insufficient for our purposes.
3 you can probably use the text in section 17.1 to specify (part of) 
some of the cast functions.  However, you do need to take care of the 
non-XML schema casting and the handling of errors.
4 rif:XMLLiteral -> rdf:XMLLiteral (in several places in the document)
5 conversion between IRIs and strings cannot be defined as a function. 
It could be defined as a predicates.  Please recall the discussion and 
the revised definition in [1].

- I wonder what the justification is for just retaining the language in 
the cast from text to string
- section 4.7: I don't really like the name of the function ("lang"); 
this sounds more like the name of an attribute.  I would prefer using 
the Xquery convention: lang-from-text

Best, Jos

[1] http://lists.w3.org/Archives/Public/public-rif-wg/2008Mar/0023.html
-- 
Jos de Bruijn            debruijn@inf.unibz.it
+390471016224         http://www.debruijn.net/
----------------------------------------------
An expert is a person who has made all the
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field.
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Received on Friday, 30 May 2008 11:39:20 GMT

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