W3C home > Mailing lists > Public > public-sparql-dev@w3.org > October to December 2015

Re: CONSTRUCT an RDF Datest

From: Tara Athan <taraathan@gmail.com>
Date: Sun, 29 Nov 2015 18:40:17 -0500
To: public-sparql-dev@w3.org
Message-ID: <565B8CE1.9020401@gmail.com>
On a related note, I see that ARQ Construct quad could easily be used to 
construct quads where the name is a blank node. Having the quad name be 
a blank node is fine according to RDF 
http://www.w3.org/TR/rdf11-datasets/#sec-introduction (and is desirable 
in my usecase), but is not permitted according to SPARQL. Are such quads 
accepted in practice, or does this cause significant interoperability 
problems?

Tara


On 11/29/15 9:19 AM, Andy Seaborne wrote:
> On 29/11/15 12:49, Tara Athan wrote:
>> On 11/29/15 5:33 AM, Andy Seaborne wrote:
>>> On 29/11/15 01:45, Tara Athan wrote:
>>>> Update: In a private reply, someone mentioned that it is possible to
>>>> create and update named graphs in a Graph Store, e.g. with the SPARQL
>>>> Update language. However, in my usecase, I am only interested in
>>>> creating an immutable RDF Dataset, not a mutable Graph Store. This 
>>>> hint
>>>> was useful in letting me see what a CONSTRUCT for an RDF Dataset might
>>>> look like, though (patterned after INSERT).
>>>>
>>>> For example, suppose I want to filter an RDF Dataset to extract a new
>>>> dataset where only named graphs having a metadata triple in the 
>>>> default
>>>> graph matching a certain filter are retained. It might be expressed 
>>>> so:
>>>>
>>>> CONSTRUCT
>>>>   { ?name ex:observedAt ?date
>>>>    GRAPH ?name
>>>>     { ?s ?p ?o}
>>>> }
>>>> WHERE
>>>>   {
>>>>    { ?name ex:observedAt ?date }
>>>>    GRAPH ?name
>>>>        {?s ?p ?o}
>>>>    FILTER (?date > 2015-06-01)
>>>> }
>>>
>>> In this particular example, do the results need to exactly conform to
>>> the structure of the dataset?  If the ex:observedAt is put in the
>>> results in the same graph:
>>>
>>> CONSTRUCT
>>>   { ?name ex:observedAt ?date
>>>     ?s ?p ?o
>>> }
>>> WHERE ...
>> In this particular example, the aim is to reproduce the original
>> structure of the dataset.
>>>
>>>>
>>>> Is there any theoretical or technical obstacle to this?
>>>
>>> There's no obstacle.  A Google Summer of Code project added this to
>>> Apache Jena this year and it'll be in the next release.
>>>
>>> It follows the design you gave:
>>>
>>> https://jena.apache.org/documentation/query/construct-quad.html
>> Thanks - that is exactly what I was looking for!
>>
>> Now with a Jena implementation in place, what is the likelihood that
>> this extended CONSTRUCT syntax will get incorporated into the SPARQL
>> Standard?
>
> (personal opinions - I do not speak for W3C)
>
> There is a better way, which is for the implementations and 
> contributing users to converge on a design, maybe through a W3C 
> community group, maybe just discuss here.
>
> That way, biases towards relatively obvious incremental improvements. 
> That is not the dynamics of a working group in my experience.
>
> This is happening in the area of tests.
>   https://www.w3.org/community/rdf-tests/
> with a community group
>
> The standards are what they are and we're not in green field of new 
> technology anymore.  There are people and companies working with 
> existing standards and as well as all the writing and teaching that 
> has gone around them.
>
>     Andy
>
> Technical details in message to james.
>
>>
>> Tara
>>>
>>>     Andy
>>>
>>>>
>>>> Tara
>>>>
>>>
>>>
>>>
>>
>>
>
>
>
Received on Sunday, 29 November 2015 23:41:05 UTC

This archive was generated by hypermail 2.3.1 : Sunday, 29 November 2015 23:41:05 UTC