On 06/02/15 06:45, Milorad Tosic wrote:
Hi Daniel,
As you correctly noted, default graph of a dataset shouldn't depend on a query.
In other words, default graph depends on the dataset but neither on a SPARQL
endpoint nor on a specific SPARQL query. Since the second case is a query
dependent interpretation it should not be correct interpretation of a default
graph.
Regards,Milorad
From: Daniel Hernández <[email protected]>
To: [email protected]
Sent: Thursday, February 5, 2015 11:37 PM
Subject: A question about service descriptions
Hello, this question is about the SPARQL specification.
A service description can include a property UnionDefaultGraph. I'm not
sure what it means. I have two possible interpretations:
1. If the default dataset of the service is {G0, (u1,G1), ..., (un,Gn)}
then it means that G0 is the union of G1,...,Gn.
Yes.
2. If a query with a dataset description FROM a FROM b is sent to the
service then the default graph of the query dataset will be the union of
the graphs resulting of dereferencing a and b, i.e., the service does
not do the merge as it is stated in the SPARQL specification.
FROM and FROM NAMED are used to describe the dataset to be queried.
FROM names all the graph for the default model (unioned together) and
FROM NAMED all the named graphs (each with a name). This is how it is
in SPARQL 1.0 and 1.1, not to do with service description.
FROM <a>
FROM <b>
describes a graph formed by reading <a> and <b> into the same graph.
UnionDefaultGraph is not referring to this feature.
<a> and <b> are not named graphs and don't show in GRAPH.
Many SPARQL services with a fixed dataset do not support FROM, FROM
NAMED. The datasets is fixed and can't be set by description.
((
In TDB FROM and FROM NAMED are drawn from the underlying datastore, not
read in from the web. And this is not tdb:unionDefaultGraph.
https://jena.apache.org/documentation/tdb/dynamic_datasets.html
))
Andy
How I must interpret it?
Thanks!
Daniel
Andy
