Re: Extending SPARQL XML result format from Bijan Parsia on 2018-07-11 (public-sparql-dev@w3.org from July to September 2018)

From: Bijan Parsia <bijan.parsia@manchester.ac.uk>
Date: Wed, 11 Jul 2018 15:24:24 +0000
To: Dan Brickley <danbri@danbri.org>
CC: Thomas Francart <thomas.francart@sparna.fr>, Martynas Jusevičius <martynas@atomgraph.com>, "Olivier Rossel" <olivier.rossel@gmail.com>, Gregory Williams <greg@evilfunhouse.com>, "public-sparql-dev@w3.org" <public-sparql-dev@w3.org>
Message-ID: <BEEEFB27-AE04-417C-9320-BBE5ED297868@manchester.ac.uk>
My hypothesis is that if a client is doing post validation validating it will do so on all formats.

In general, the probably would be for clients that produce application objects which might not have slots for the extra data and thus either hork or strip it.

(This is all speculation.)

(Oh and in my wrap and strip version you could always insert and strip.)

On Jul 11, 2018, at 16:18, Dan Brickley <danbri@danbri.org<mailto:danbri@danbri.org>> wrote:

Would the JSON format be easier to extend without concern for fragile clients?

Dan

On Wed, 11 Jul 2018, 08:15 Thomas Francart, <thomas.francart@sparna.fr<mailto:thomas.francart@sparna.fr>> wrote:
Hello

My concern (if any) is not about Jena, which is doing exactly what it is supposed to do; my concern is with the SPARQL XML Result Format recommendation, which do not allow any extension point.

I guess I could also define my own result format, and respond with either the standard SPARQL result XML format, or my own "extended" result format, based on content negociation.
The SPARQL protocol does not say explicitely that other types of results formats are allowed besides SPARQL/XML, JSON, CSV or TSV, but I guess it should be possible to do this.

"

The response body of a successful query operation with a 2XX response is either:

  *   a SPARQL Results Document in XML<http://www.w3.org/TR/rdf-sparql-XMLres/>, JSON<http://www.w3.org/TR/sparql11-results-json/>, or CSV/TSV<http://www.w3.org/TR/sparql11-results-csv-tsv/> format (for SPARQL Query forms SELECT<http://www.w3.org/2001/sw/DataAccess/rq23/#select> and ASK<http://www.w3.org/2001/sw/DataAccess/rq23/#ask>); or,
  *   an RDF graph [RDF-CONCEPTS<https://www.w3.org/TR/2013/REC-sparql11-protocol-20130321/#rdf-concepts>] serialized, for example, in the RDF/XML syntax<http://www.w3.org/TR/rdf-syntax-grammar/> [RDF-XML<https://www.w3.org/TR/2013/REC-sparql11-protocol-20130321/#rdf-xml>], or an equivalent RDF graph serialization, for SPARQL Query forms DESCRIBE<http://www.w3.org/2001/sw/DataAccess/rq23/#describe> and CONSTRUCT<http://www.w3.org/2001/sw/DataAccess/rq23/#construct>).

The content type of the response to a successful query operation must be the media type defined for the format of the response body.

"

Best Regards
Thomas


2018-07-11 15:25 GMT+02:00 Martynas Jusevičius <martynas@atomgraph.com<mailto:martynas@atomgraph.com>>:
Probably better to take Jena-specific questions to its own list:
https://jena.apache.org/help_and_support/


On Wed, Jul 11, 2018 at 2:49 PM, Thomas Francart
<thomas.francart@sparna.fr<mailto:thomas.francart@sparna.fr>> wrote:
> Olivier, you have the reference to the code in the stacktrace excerpt I
> posted. See
> https://github.com/apache/jena/blob/0366da2c37b64978893897eba068fdb6b47ea782/jena-arq/src/main/java/org/apache/jena/riot/resultset/rw/ResultsStAX.java#L281

>
> Thomas
>
> 2018-07-11 14:46 GMT+02:00 Olivier Rossel <olivier.rossel@gmail.com<mailto:olivier.rossel@gmail.com>>:
>>
>> Did you check which code in Jena triggers the schema validation? I don't
>> see this as a so strong requirement.
>>
>> Le mer. 11 juil. 2018 à 14:37, Thomas Francart <thomas.francart@sparna.fr<mailto:thomas.francart@sparna.fr>>
>> a écrit :
>>>
>>> Hello
>>>
>>> Trying to parse the following extended SPARQL result XML works in RDF4J
>>> but fails in Jena.
>>> Conclusion : SPARQL XML result format is not extensible from the standard
>>> point of view, neither from a practical point of view if one of the major
>>> RDF library fails in dealing with this (with reason, since the standard does
>>> not allow it). Using other namespaces does not help. I will consider using a
>>> "Link" header in the HTTP response, as suggested.
>>>
>>> Best Regards
>>> Thomas
>>>
>>> XML :
>>>
>>> <?xml version="1.0"?>
>>> <sparql xmlns="http://www.w3.org/2005/sparql-results#">
>>>   <meta xmlns="http://sparna.fr/sparql-results-extension#">
>>>     <timeMillis
>>> xmlns="http://sparna.fr/sparql-results-extension#">123456</timeMillis>
>>>   </meta>
>>>   <head>
>>>     <variable name="concept"/>
>>>     <variable name="prefLabel"/>
>>>   </head>
>>>   <results>
>>>     <result>
>>>       <binding name="concept">
>>>         <uri>http://vocabularies.unesco.org/thesaurus/concept9331</uri>
>>>       </binding>
>>>       <binding name="prefLabel">
>>>         <literal xml:lang="en">Teacher education</literal>
>>>       </binding>
>>>     </result>
>>>   </results>
>>> </sparql>
>>>
>>> Code with RDF4J :
>>>
>>>
>>> TupleQueryResultParserRegistry.getInstance().get(TupleQueryResultFormat.SPARQL).get().getParser().parseQueryResult(new
>>> FileInputStream("/path/to/sparql-result-extended.xml"));
>>>
>>> Code with Jena :
>>>
>>> ResultSetMgr.read(new
>>> FileInputStream("/path/to/sparql-result-extended.xml"),
>>> ResultSetLang.SPARQLResultSetXML);
>>>
>>> Exception :
>>>
>>> Caused by: org.apache.jena.sparql.resultset.ResultSetException:
>>> skipToHead: Unexpected tag: {http://sparna.fr/sparql-results-extension#}meta<http://sparna.fr/sparql-results-extension#%7Dmeta>
>>>     at
>>> org.apache.jena.riot.resultset.rw.ResultsStAX.staxError(ResultsStAX.java:466)
>>>     at
>>> org.apache.jena.riot.resultset.rw.ResultsStAX.skipTo(ResultsStAX.java:282)
>>>
>>>
>>>
>>>
>>>
>>> 2018-07-09 19:36 GMT+02:00 Gregory Williams <greg@evilfunhouse.com<mailto:greg@evilfunhouse.com>>:
>>>>
>>>> FWIW, the hacky but standards compliant way I’ve dealt with this in the
>>>> past is by using the link element with a data: URI.
>>>>
>>>> .greg
>>>>
>>>> On Jul 9, 2018, at 10:10 AM, Thomas Francart <thomas.francart@sparna.fr<mailto:thomas.francart@sparna.fr>>
>>>> wrote:
>>>>
>>>> Hello
>>>>
>>>> Thanks for your answers, here is slightly more extended description of
>>>> the use-case : I am preparing a "SPARQL query mediator", that is a
>>>> SPARQL-compatible service that will send the same query to multiple sources
>>>> and aggregate the results into a single resultset. It can also articulate
>>>> part of the query with other datasources (like if the SERVICE keyword was
>>>> used). This involves preprocessings on the query, and post-processing on the
>>>> result sets.
>>>>
>>>> I would like the SPARQL client to know if one of the source has reached
>>>> a LIMIT number of results (I plan to limit the number of results to X for
>>>> each source)
>>>> I was also thinking about proving the "explain" of the query processing
>>>> if the SPARQL client asked for it (which sources were queried, how the query
>>>> got transformed, etc;)
>>>>
>>>> So the information could be pretty structured and does not seem to fit
>>>> well in HTTP headers.
>>>>
>>>> Thanks for your ideas. I might try parsing with additionnal XML elements
>>>> and let you know.
>>>>
>>>> Best Regards
>>>> Thomas
>>>>
>>>>
>>>> 2018-07-09 13:56 GMT+02:00 Olivier Rossel <olivier.rossel@gmail.com<mailto:olivier.rossel@gmail.com>>:
>>>>>
>>>>> Can't the HTTP headers contain such informations, instead of the XML
>>>>> resultSet ?
>>>>>
>>>>> Le lun. 9 juil. 2018 à 13:38, Martynas Jusevičius
>>>>> <martynas@atomgraph.com<mailto:martynas@atomgraph.com>> a écrit :
>>>>>>
>>>>>> Have you tried parsing?
>>>>>>
>>>>>> I think if you used XML elements in your own namespace, it should not
>>>>>> be a problem.
>>>>>>
>>>>>> But probably better to start by explaining what your use case is,
>>>>>> rather than the solution you think you need.
>>>>>>
>>>>>> On Mon, Jul 9, 2018 at 1:31 PM, Thomas Francart
>>>>>> <thomas.francart@sparna.fr<mailto:thomas.francart@sparna.fr>> wrote:
>>>>>> > Hello
>>>>>> >
>>>>>> > I would like to extend a SPARQL XML result format with custom header
>>>>>> > information; such as query execution time, warning if a search limit
>>>>>> > was
>>>>>> > reached during query execution, or other king of meta-information
>>>>>> > about the
>>>>>> > resultset.
>>>>>> >
>>>>>> > From the definition of the SPARQL XML result format at
>>>>>> > https://www.w3.org/TR/rdf-sparql-XMLres/#schemas, I don't see the
>>>>>> > XML schema
>>>>>> > allows this; there is no extension point. Could someone confirm ?
>>>>>> >
>>>>>> > In practice, would it be possible to have something like :
>>>>>> >
>>>>>> > <?xml version="1.0"?>
>>>>>> > <sparql xmlns="http://www.w3.org/2005/sparql-results#">
>>>>>> >
>>>>>> >   <meta>
>>>>>> >
>>>>>> >     <!-- here put some meta information -->
>>>>>> >
>>>>>> >   </meta>
>>>>>> >
>>>>>> >
>>>>>> >   <head>
>>>>>> >
>>>>>> >     ...
>>>>>> >
>>>>>> >   </head>
>>>>>> >
>>>>>> >   <results>
>>>>>> >     ...
>>>>>> >   </results>
>>>>>> >
>>>>>> > </sparql>
>>>>>> >
>>>>>> >
>>>>>> >
>>>>>> > Would SPARQL result parsers choke on this ? RDF4J ? Jena ?
>>>>>> > Is anyone already using this technique ?
>>>>>> >
>>>>>> > Thanks
>>>>>> > Thomas
>>>>>> >
>>>>>> > --
>>>>>> >
>>>>>> > Thomas Francart - SPARNA
>>>>>> > Web de données | Architecture de l'information | Accès aux
>>>>>> > connaissances
>>>>>> > blog : blog.sparna.fr<http://blog.sparna.fr>, site : sparna.fr<http://sparna.fr>, linkedin :
>>>>>> > fr.linkedin.com/in/thomasfrancart<http://fr.linkedin.com/in/thomasfrancart>
>>>>>> > tel :  +33 (0)6.71.11.25.97, skype : francartthomas
>>>>>>
>>>>
>>>>
>>>>
>>>> --
>>>>
>>>> Thomas Francart - SPARNA
>>>> Web de données | Architecture de l'information | Accès aux connaissances
>>>> blog : blog.sparna.fr<http://blog.sparna.fr>, site : sparna.fr<http://sparna.fr>, linkedin :
>>>> fr.linkedin.com/in/thomasfrancart<http://fr.linkedin.com/in/thomasfrancart>
>>>> tel :  +33 (0)6.71.11.25.97, skype : francartthomas
>>>
>>>
>>>
>>>
>>> --
>>>
>>> Thomas Francart - SPARNA
>>> Web de données | Architecture de l'information | Accès aux connaissances
>>> blog : blog.sparna.fr<http://blog.sparna.fr>, site : sparna.fr<http://sparna.fr>, linkedin :
>>> fr.linkedin.com/in/thomasfrancart<http://fr.linkedin.com/in/thomasfrancart>
>>> tel :  +33 (0)6.71.11.25.97, skype : francartthomas
>
>
>
>
> --
>
> Thomas Francart - SPARNA
> Web de données | Architecture de l'information | Accès aux connaissances
> blog : blog.sparna.fr<http://blog.sparna.fr>, site : sparna.fr<http://sparna.fr>, linkedin :
> fr.linkedin.com/in/thomasfrancart<http://fr.linkedin.com/in/thomasfrancart>
> tel :  +33 (0)6.71.11.25.97, skype : francartthomas



--

Thomas Francart - SPARNA
Web de données | Architecture de l'information | Accès aux connaissances
blog : blog.sparna.fr<http://blog.sparna.fr>, site : sparna.fr<http://sparna.fr>, linkedin : fr.linkedin.com/in/thomasfrancart<https://fr.linkedin.com/in/thomasfrancart>
tel :  +33 (0)6.71.11.25.97, skype : francartthomas
Received on Wednesday, 11 July 2018 15:24:52 UTC