On 24/08/12 14:29, Simon Helsen wrote:
Andy,
ok, thanks for the clarification. No, I really meant
FROM <graphUri1>
FROM NAMED <graphUri2>
because we thought that unionDefaultGraph=true would still affect the
explicit (dynamic) dataset.
There is always a default graph.
If it is not specified, and unionDefaultGraph is false/undef, it is an
empty graph.
If it is not specified, and unionDefaultGraph is true, it is the union
of supplied named graphs.
If it is specified, it is the merge of all FROM clauses.
Here, you specified it.
Andy
Simon
From: Andy Seaborne <[email protected]>
To: [email protected]
Date: 08/24/2012 06:26 AM
Subject: Re: mixing FROM and FROM NAMED with unionDefaultGraph=true
------------------------------------------------------------------------
On 23/08/12 22:51, Simon Helsen wrote:
> Hi guys,
>
> I have a question which may or may not be a defect, but I need some input
> first.
>
> If you run with unionDefaultGraph==true and you have the following
type of
> query:
>
> SELECT ?o
> FROM <graphUri1>
> FROM NAMED <graphUri2>
> WHERE { ?s <somePredicate> ?o }
>
> I would expect the pattern to match triples in both graphUri1 and
> graphUri2.
The dataset description is:
FROM <graphUri1>
FROM NAMED <graphUri2>
so the default graph is contents of <graphUri1>
unionDefaultGraph is irrelevant - you've overridden it by providing a
dataset description.
Did you mean:
FROM <graphUri1>
FROM <graphUri2>
which makes the default the (calculated) merge of 1 and 2.
> Currently, TDB/ARQ does not do this, but only picks matches
> from graphUri1. Given that unionDefaultGraph=true should merge all named
> graphs into the default graph, this is surprising. To elaborate a bit, we
> found that the following query
>
> SELECT ?o
> FROM NAMED <graphUri2>
> WHERE { ?s <somePredicate> ?o }
Bug.
If you specify the dataset description, you are giving a complete
description. There is an empty default graph in that description.
> does pick results from graphUri2 (when run with unionDefaultGraph==true).
> Also, when we execute the following query:
>
> SELECT ?o
> FROM <graphUri1>
> FROM NAMED <graphUri2>
> WHERE { graph ?g { ?s <somePredicate> ?o } }
>
> then tdb seems to pick results from graphUri2 which is as expected.
>
> We were thinking that explicit FROM/FROM NAMED clauses simply ignores the
> unionDefaultGraph=true switch which could then explain the behavior
of the
> first query above, but it doesn't explain the one of the second query.
>
> Feedback on this is welcome.
>
> thanks,
>
> Simon
>
