Ok, thanks for the clarifications. The first thing to understand is
that these examples are created from a database perspective where the
query is applied to a database with some named graphs. When using
TopBraid Composer or Live, you are using a server perspective where
there can be multiple database references, file serializations, etc.
To access a named graph in one of those databases necessarily involves
a level of indirection: you need to identify the database and the
named graph.
For SDB, there are three different contexts for named graphs to
consider:
1) an unnamed graph - this is a separate graph that does not have a
name (triples only, not a quad)
2) a named graph (quad storage)
3) the union of all graphs
Note that 1) and 3) are different. The union graph will include the
unnamed graph and all named graphs.
Given this, you can set the context of a query to the union graph for
the SDB database with the FROM statement in SPARQL:
SELECT *
FROM <base URI of union graph>
WHERE {
GRAPH ?g {?s ?p ?o}
}
The second step is to get the base URI of the union graph for your SDB
data store. To do this create a connector file (New > Jena SDB
connector) that specifies "urn:x-arq:UnionGraph" as the SDB Named
Graph URI.
The use of connector files may need a bit of explanation. It's key to
understand that Composer/Live use a named graph structure throughout
its workspace, using the base URI as the name of the graph. This not
only addressed the indirection necessary to address multiple
databases, but integrates nicely with owl:imports which also uses URIs
to identify the imported graphs. Each connector creates a base URI
that holds information about what data set (where a "data set" can be
anything that has a named graph structure) to address and the named
graph within that data set. This goes for the union graph, which is a
specific type of graph in SDB, as well as named (and unnamed) graphs.
Again, the added level of indirection is necessary because Composer is
using a server model (workspace consisting of many connections) and
the examples are using a single data store model (one connection).
-- Scott
On Apr 6, 9:58 am, DaveL <[email protected]> wrote:
> Scott,
>
> I am using TBC 3.4.0.
>
> The general form of the query was taken
> fromhttp://www.cambridgesemantics.com/2008/09/sparql-by-example/#%2833%29
> .
>
> The exact query I am running (slightly edited to remove propriety
> information) is:
>
> PREFIX rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#>
> PREFIX cc: <http://anchor/example#>
> SELECT *
> WHERE
> {
> { ?s rdf:type cc:exampleType }
> UNION
> { GRAPH ?g { ?s rdf:type cc:exampleType } }
>
> }
>
> The intent is to return all named graphs which contain resources of
> rdf:type "exampleType."
>
> This query works perfectly when executed via the Jena/SDB
> QueryExecution class, by code (excerpted) here:
>
> Dataset ds = DatasetStore.create(store); // an SDB Store
> Query query = QueryFactory.create("---the above query---"));
> QueryExecution qe = QueryExecutionFactory.create(query, ds );
> try {
> ResultSet rs = qe.execSelect();
> ResultSetFormatter.out(rs);
> } finally {
> qe.close();
> }
>
> Thanks for any comments,
>
> Dave
>
> On Apr 5, 6:23 pm, Scott Henninger <[email protected]> wrote:
>
> > Dave; We'd need a couple of follow-up to look into this properly.
> > First is what version of TBC-ME are you using? The second is what
> > specific query template are you using?
>
> > To access an existing SDB database, you'd need to use the same New >
> > RDF/OWL Jena SDB Database Connection, and fill in the information on
> > the relational database where the data is store. Note that this
> > wizard only creates a connection to an existing data store. There
> > aren't any stricter requirements for using a .sdb connector.
>
> > -- Scott
>
> > On Apr 5, 3:24 pm, DaveL <[email protected]> wrote:
>
> > > Having read the discussion last month about Named Graphs, I find
> > > myself still a bit confused.
>
> > > I'm developing an OWL app which uses SDB as the repository. In the
> > > repository are many Models which are named graphs representing
> > > resources, and some Models which are ontologies (referenced by the
> > > resources, via the SDB DocumentManager).
>
> > > I tried connecting to this pre-existing store from TBS (Maestro
> > > Edition), and had a couple of odd results.
>
> > > First, if I create the .sdb file using the wizard under New / RDF/OWL
> > > Jena SDB Database Connection, I can access the default graph (if I
> > > don't fill in the "Named Graph URI" field, or any specific graph if I
> > > put its URI in the field, but there doesn't appear to be a way to
> > > access the database as a whole. For example, I'd like to be able to
> > > query for all graphs which contain a triple matching a pattern. The
> > > template for doing this (in the SPARQL by example presentation)
> > > doesn't work for me.
>
> > > Second, re-opening an existing .sdb file never seems to work. An
> > > exception is invariably thrown:
>
> > > "Could not load \TopBraid\SDBRepository.sdb or one of its imports.
> > > The most recent URI washttp://localhost/dataStore
> > > No matching StoreCache entry found"
>
> > > Once I get this error I must restart TBS before I can look at the
> > > database again.
>
> > > Any guidance on what this means? Are there stricter requirements for
> > > the contents of the database than I am aware of, for example? (Things
> > > I must add to be TBS-compatible, for example. I note a reference in
> > > the .sdb file to a "config" model that I don't create...)
>
> > > Thanks,
>
> > > Dave Lebling
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