Andy, thanks for your answer. It solve my question. Milorad, I'm not sure if I understand your assertion "default graph of a dataset shouldn't depend on a query", as the default graph can be described in a query using named graphs. Also, I does not understand your assertion that a default graph does not depends on an edpoint, because the SPARQL specification stated that when no dataset description is provided in the query or in the request parameters (specified in the SPARQL protocol), then the dataset is provided by the endpoint, i.e., a default dataset is used.
Regards, Daniel On Fri, 2015-02-06 at 09:46 +0000, Andy Seaborne wrote: > 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 > > > > > > > > >
