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Re: RDF 2.0 Wishlist - Legal RDF which I can't SPARQL

From: Andy Seaborne <andy.seaborne@epimorphics.com>
Date: Thu, 29 Jul 2010 19:58:54 +0100
Message-ID: <4C51CF6E.2030002@epimorphics.com>
To: Mischa Tuffield <mischa.tuffield@garlik.com>
CC: Paul Gearon <gearon@ieee.org>, Damian Steer <pldms@mac.com>, Semantic Web <semantic-web@w3.org>


On 29/07/2010 6:59 PM, Mischa Tuffield wrote:
>
> On 29 Jul 2010, at 18:40, Andy Seaborne wrote:
>
>> On 29/07/2010 6:22 PM, Paul Gearon wrote:
>> > On Thu, Jul 29, 2010 at 1:13 PM, Paul Gearon<gearon@ieee.org
>> <mailto:gearon@ieee.org>> wrote:
>> >
>> > <snip/>
>> >
>> >> In a hack similar to the one I mentioned with FILTER, but you can
>> always say:
>> >>
>> >> insert { graph<http://example.com/graph> {
>> >> ?u foo:Property "something" } }
>> >> { { select IRI("http://example.com/mylamefoafdocument`uri") as ?u
>> {} } }
>
> This is dependant on the definition of the function "IRI()", and it
> seems odd to me, based on the function name, that it would generate an
> illegal IRI.
>
>>
>> but it still isn't a legal IRI.
>
> :)

There is a function in "XQuery 1.0 and XPath 2.0 Functions and 
Operators" what might help:

fn:encode-for-uri(string) ->string

http://www.w3.org/TR/xpath-functions/#func-encode-for-uri

although it will encode "/" and ":" as well as it's intended to produce 
a string that can be used in a URI path segment not make a string safe 
to use as an IRI.


The SPARQL-WG is discussing defining a core set of functions to be part 
of spec (so any implementation can be expected to provide them): e.g.

http://www.w3.org/2009/sparql/wiki/Feature:FunctionLibrary#XQuery_1.0_and_XPath_2.0_Functions_and_Operators

(disclosure: I produced that list - by simply looking through the F&O 
functions that covered datatypes required by SPARQL and made sense to 
SPARQL)

Either adding a <make-safe-for-absolute-iri>(string)->string or making 
IRI do minimal encoding necessary are possible.

>
>>
>> There are two levels here:
>>
>> The syntax, that says:
>>
>> IRI_REF ::= '<' ([^<>"{}|^`\]-[#x00-#x20])* '>'
>>
>> but also the syntax rules in the URI RFC (now RFC 3986) including any
>> scheme-specific rules.
>>
>> Last time, IIRC DAWG decided not to copy over the full grammar for
>> IRIs, but to put in a more general but smaller pattern.
>>
>> For example, "[" "]" are only legal as delimiters for IPv6 addresses
>> in the authority part.
>>
>> Andy
>
> Am guessing I should have just emailed the SPARQL WG people, but I
> thought I would also flag this matter with the RDF 2.0 folks.

It's an RDF-maintenance question.  (not 2.0 please!)

IMO SPARQL should follow, not lead, the decision for the data.  The 
original IRI decision in DAWG was made taking forward the reasoning that 
the RDF-Core group had used, just made up-to-date because by then the 
updated URI and the IRI RFCs had come out.

	Andy

>
> Cheers,
>
> Mischa
Received on Thursday, 29 July 2010 18:59:47 UTC

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