Re: Restpark - Minimal RESTful API for querying RDF triples

On 16/04/2013 20:44, Kingsley Idehen wrote:
> On 4/16/13 3:28 PM, Aidan Hogan wrote:
>>
>> In practice, it is not at all difficult to find (interesting) SPARQL
>> queries that existing engines cannot run completely and correctly. I
>> (unfortunately) find them all the time without even trying.
>>
>> SPARQL evaluation does not scale, cannot scale, will never scale.
>
> That should depend on the combination of query, dataset size, computing
> power, and SPARQL engine quality. In the worst case, the query should
> simple conclude: I cannot provide a solution within the time allotted,
> so give me more time....

The ability to answer "I don't know" or "cannot compute right now" or "I 
need more time" would make anything trivially scalable. But "I don't 
know" or "cannot compute" or "I need more time" is not a valid SPARQL 
answer. Nor is stopping after the first X answers are returned.

The SPARQL standard does not limit query complexity or dataset size. 
Your caveats need to be applied to the claim that "SPARQL scales", not 
to the claim that "SPARQL doesn't scale".

Had you said "SPARQL scales in some cases ... depending on the 
combination of query, dataset size, computing power, and SPARQL engine 
quality", that would be fine with me.

But with the same caveats, I could equally say that OWL 2 Full or OWL 2 
DL reasoning scales. Had I said "OWL 2 DL scales", I would sincerely 
hope that someone on the list would say something to correct me.

> I would be very happy to look at some of those queries thrown at the
> instance we maintain at: http://lod.openlinksw.com . It has a massive
> data collection (50+ billion triples) and a publicly accessible SPARQL
> endpoint. As I said, your worst case should be: give me more time to
> compute a solution or the query optimizer has determined that your
> solution simply requires too much computing resources etc..

I like the service. I use it often. :) But again, "give me more time" or 
"your query is too expensive" is not a valid SPARQL answer.

> Back to you, send me SPARQL queries or SPARQL protocol URLs.

	http://lod.openlinksw.com/sparql

I want *valid SPARQL answers* for:

	SELECT * WHERE
	{?s foaf:knows ?o}

or

	SELECT * WHERE
	{?s foaf:knows ?o . ?o foaf:knows ?o2 .}

to start with. :)

Cheers,
Aidan

Received on Tuesday, 16 April 2013 20:15:36 UTC