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RE: SWRL string builtins -- suggestion

From: <massimo@w3.org>
Date: Thu, 3 Jun 2004 10:12:16 -0400 (EDT)
Message-ID: <3152.157.138.20.120.1086271936.squirrel@157.138.20.120>
To: "Neil Goldman" <ngoldman@teknowledge.com>
Cc: www-rdf-rules@w3.org

All this is a very small subpart of the much more general issue,
not just belonging to SWRL but to Semantic Web Query/Reasoning in general,
of selecting/reusing a common suitable set of functions and operators.
Cf. from the Conclusions in http://www.w3.org/Submission/2004/03/Comment:
<quote>
understanding that graceful interoperation within the RDF model and with
the XQuery functions and operators may well be the key to the success of
components of the Semantic Web.
</quote>

So, the more general issue is, rather then reinventing the wheel,
trying to find the common set that applications can understand/share/reuse.
Obvious candidate for analysis: http://www.w3.org/TR/xpath-functions/

As said, this is not much of an SWRL issue, but of any Web Query/Reasoning
application that wants to gracefully scale.

-M

ps In the very particular case of this discussion, fn:substring would do
what you want.



>
> I'm not sure what sort of abuse of a "charat" relation you are worried
> about, but certainly such abuse must already be possible via
> swrlb:substring, which allows one-character substrings to be referenced
> via rules.
>
> My feeling is that since OWL has adopted the XML schema standard datatype
> "string" it is unreasonable to place part of that standard outside the
> scope of "rules" SOLELY because it might be misused.  It is clear that the
> standard (quoted below) makes a "charat" relation well defined.  Any
> application program that obtains a  string value from OWL can readily
> obtain the integer codes of the individual charcters of that string with
> trivial library APIs available in every programming langauge.  My
> suggestion is simply that the built-ins of a rules standard should cover
> this aspect of the string type.
>
> In any case, we should not think of the type "string" as synonymous with
> "natural language text".  Strings are also used to represent fragments of
> programming language source code and network protocols and passwords and
> DNA codes and many other things which are not natural language at all.
>
> ===========from http://www.w3.org/TR/2000/WD-xmlschema-2-20000225
> 3.2.1 string
> [Definition:]  The string datatype represents character strings in XML.
> The value space of string is the set of finite sequences of UCS characters
> ([ISO 10646] and [Unicode]). A UCS character (or just character, for
> short) is an atomic unit of communication; it is not further specified
> except to note that every UCS character has a corresponding UCS code
> point, which is an integer. The ordered property of string is the
> [Unicode] character number sequence
>
>> -----Original Message-----
>> From: Martin Duerst [mailto:duerst@w3.org]
>> Sent: Monday, May 31, 2004 1:07 AM
>> To: Neil Goldman; www-rdf-rules@w3.org
>> Cc: Neil Goldman
>> Subject: Re: SWRL string builtins -- suggestion
>>
>>
>> This may be a bad idea. In English, a lot of functions on strings
>> can be implemented by using functions on individual characters of
>> the string. So a 'charAt' function seems very tempting. But in
>> many other languages, things are not as simple as that. Of course
>> this depends on the operation and the language.
>>
>> Regards,    Martin.
>>
>> At 16:45 04/05/28 -0700, Neil Goldman wrote:
>>
>> >I believe the string builtins should provide a means to get to an
>> >individual character, not just to a string of length 1.
>> >It would suffice to provide:
>> >
>> >swrlb:charAt
>> >Satisfied iff the first argument is equal to the character
>> code of the
>> >character in the string second argument appearing at index
>> third argument
>> >
>> >====================> >
>> >Neil Goldman              Tel:   (310)578-5350 x204
>> >Teknowledge Corporation   Fax:   (310)578-5710
>> >Suite 1010
>> >4640 Admiralty Way
>> >Marina del Rey, CA 90292
>>
>>
>>
>
Received on Thursday, 3 June 2004 10:12:16 GMT

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