bigdata-developers

[Bigdata-developers] Listing named graphs in Wikidata service

[Ghislain A. <ghi...@gm...>]

Hi,
I wanted to test the use of the queries below to list named graphs (if any)
in wikidata service [a]. I've tried them without success:

1- select distinct ?g { graph ?g {} }
2- select distinct ?g { graph ?g {?s ?p ?o} }
3- select (count(distinct ?g) as ?count) { graph ?g {} }

Are those queries not standard or just taking too much time because of the
underlying dataset | time out settings?

In general, is there a way to reduce the time execution of such "useful"
query in public endpoints with billions of data

TIA
Best,
Ghislain
PS: I note that there are errors when trying to use DBpedia endpoint for
queries #1 and #3. The result of query #2 is a bit strange.
[a] https://query.wikidata.org/

-- 
-------
"Love all, trust a few, do wrong to none" (W. Shakespeare)
Web: http://atemezing.org

Re: [Bigdata-developers] Listing named graphs in Wikidata service

[Stas M. <sma...@wi...>]

Hi!

> I wanted to test the use of the queries below to list named graphs (if
> any) in wikidata service [a]. I've tried them without success: 

We do not use any subgraphs in WDQS, so I don't think that query would
produce much of a useful result.

-- 
Stas Malyshev
sma...@wi...

Re: [Bigdata-developers] Listing named graphs in Wikidata service

[Ghislain A. <ghi...@gm...>]

Thanks Stas!
It's clear that a user might ask any type of query from an endpoint
according to her needs.
My concern goes further on whether such queries are valid or not in the
underlying RDF graph (in this case BLZ) regarding SPARQL 1.1 spec.
You agree with me that this query :
`select distinct ?g { graph ?g {?s ?p ?o} }` seems to be a valid SPARQL
query, but throws an error in WDQS service [1].

Any thoughts on this?
Best,
Ghislain
[1] https://goo.gl/hdJwUk


El jue., 20 abr. 2017 a las 21:54, Stas Malyshev (<sma...@wi...>)
escribió:

> Hi!
>
> > I wanted to test the use of the queries below to list named graphs (if
> > any) in wikidata service [a]. I've tried them without success:
>
> We do not use any subgraphs in WDQS, so I don't think that query would
> produce much of a useful result.
>
> --
> Stas Malyshev
> sma...@wi...
>
-- 
-------
"Love all, trust a few, do wrong to none" (W. Shakespeare)
Web: http://atemezing.org

Re: [Bigdata-developers] Listing named graphs in Wikidata service

[Stas M. <sma...@wi...>]

Hi!

> You agree with me that this query :
> `select distinct ?g { graph ?g {?s ?p ?o} }` seems to be a valid SPARQL
> query, but throws an error in WDQS service [1]. 

It is a valid SPARQL query, but what you're essentially asking is to
download whole 1.8b triples in a single query. There's no way we can
deliver this in one minute, which is current constraint on queries,
neither we want to enable queries like this - they are very
resource-intensive and serve little purpose.

If you want to work with huge data sets or import the whole data, you
may look either into getting the dump download and processing it with
offline tools like Wikidata Toolkit[2], or using our LDF server[1] which
is lightweight and allows you to work with the data much more efficiently.

[1]
https://www.mediawiki.org/wiki/Wikidata_query_service/User_Manual#Linked_Data_Fragments_endpoint
[2] https://www.mediawiki.org/wiki/Wikidata_Toolkit
-- 
Stas Malyshev
sma...@wi...