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Re: SPARQL: graph syntax should be N3 subset

From: Tim Berners-Lee <timbl@w3.org>
Date: Fri, 11 Mar 2005 10:38:05 -0500
Message-Id: <8FB3BF22-9243-11D9-A27C-000A9580D8C0@w3.org>
Cc: public-rdf-dawg-comments@w3.org
To: andy.seaborne@hp.com

Thank you for making the changes.

I am convinced that this is significant net benefit to the wider  
community
and to the adoption of the semantic web languages.

Tim

On Mar 11, 2005, at 5:54, Seaborne, Andy wrote:

> Tim,
>
> At the Boston face-to-face (Feb 28, March 1), the working group  
> developed a set of possible changes to the SPARQL syntax using N3 or  
> turtle like constructs for triple patterns.  The working group  
> resolved at Tuesday's telecon to make those changes.  The proposal is  
> outlined in:
>
> http://lists.w3.org/Archives/Public/public-rdf-dawg/2005JanMar/ 
> 0227.html
>
> The editors' working draft has been updated (grammar and examples).   
> Full explanation of the syntax is still to be written up.
>
> 	Andy
>
> Tim Berners-Lee wrote:
>> Reading the 2004/10/13 draft of SPARQL.
>> The grammar for SPARQL frequently involves graph patterns.   These  
>> should use the N3 grammar, specifically a subset at a level to the  
>> subset known as Turtle.
>> There advantages to the languages overlapping.
>> - Cuts the learning curve for people learning SPARQL and N3.
>> - Allows code sharing for those implementing both languages
>> - Allows data to be searched for to be pasted into a query.
>> - Allows one to create some example data, view it as N3, and then  
>> paste it into the 'construct' clause, replacing a few values with  
>> variables.
>> N3 is a very suitable syntax for this:
>> - N3 has commonly used subsets Turtle and NTriples which are widely  
>> deployed
>> - N3 is a syntax which meets exactly the same goals as SPARQL, in  
>> being concise and human-friendly representation of a graph with  
>> variables;
>> - N3 has been used in the SPARQL document itself for readability for  
>> the data.
>> - N3 has evolved in response to community needs in the RDF Interest  
>> Group and SW Interest Group.
>> N3 has come a long way since it started as a triples language:
>> - The comma and semicolon were added very early on a shortcuts making  
>> both reading and writing easier when subject [and predicate] are  
>> repeated.   While it is true that SPARQL's current individual triples  
>> form is simpler, I strongly believe that the users would tired of it  
>> once they become familiar with it.  (Similarly, the list construct  
>> for collections makes it possible to actually use lists in practice,  
>> where elaborations in terms of rdf:first and rdf:rest are  
>> impractically cumbersome.)
>> - The grammar of the language is now defined in a context-free  
>> grammar in RDF itself.
>> - Much of the actual nitty-gritty questions about the language  
>> involved details of tokenizing, sets of characters allowed for  
>> identifiers, and escaping.  The hassle comes from coordinating the  
>> XML, and N3 at the NTriples, Turtle and N3 levels, and all the  
>> parsers involved.  To have to add another randomly different language  
>> to this mix will make it more difficult.
>> - The only significant change which has been proposed is to add  
>> syntax for unordered sets similar to that for ordered collections.
>> This is a strong suggestion.  I believe that the community will be  
>> best served in making this change, and doing so as soon as possible.
>> It may be that at the same time we should plan for the  
>> standardization of N3 itself, with spcific view to keeping Ntriples  
>> Turtle SqarQL and N3 full in sync.
>> Tim Berners-Lee
>> ___________________________________________
>> PS:
>> If this is done, the N3 syntax could be extended to include the  
>> keyword-style which the group seems to prefer for SPARQL. Assuming an  
>> N3 semantics for SPARQL exists, then the sparql keywords could be  
>> deemed to add extra syntactic shortcuts to the language.
>> @keywords select, from, where, prefix, option.
>> prefix   soc: <whatever>.
>> select   ?x, ?y, ?z
>> from     <mydata.rdf>
>> where
>> 	?x    a soc:Person;
>> 		phone:number   "+1 781 555 1212";
>> 		fam:sister	?y.
>>         ?y   phone:number ?z.
>> Making SPARQL a subset of N3 would allow a SPARQL query to be quoted  
>> in an N3 document, which would allow it to be carried as a payload in  
>> more complex things, which might for example provide extra metadata  
>> about a query.
>
Received on Friday, 11 March 2005 15:38:07 GMT

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