Re: New Version of Networked Graphs Sail Available

This looks like a very interesting project. I have plans to get beta6 of
Sesame2 up and running as soon as I have time and I will take a look at this
too.

I see the power of views, but I also see potential for expressing rules. I
noticed you have a brief note about this at the project web site ("... and
to define rules (through recursive view definitions).") but could you give
an example of how this would work?

On 10/17/07, Simon Schenk <sschenk@uni-koblenz.de> wrote:
>
> Dear all,
>
> I am happy to announce version 0.3 of the Networked Graphs Sail for the
> Sesame2 RDF repository [1], which is available for download at [2].
>
> Networked Graphs are an extension of named graphs, which allow to define
> a graph both extensionally by listing triples (as in named graphs), but
> also intensionally through views. Views are expressed using SPARQL
> queries and are included into graphs using a simple RDF syntax. To
> express that some graph G should contain the results of a query Q, we
> simply add a statement (G ng:definedBy Q^^ng:Query) to G. Views can use
> negation as failure, just as normal SPARQL queries and can recursively
> depend on each other. The reasoning engine will resolve this recursion.
> A graph can at the same time contain intensionally and extensionally
> defined statements.
>
> A detailed specification of Networked graphs can be found in [3].
>
> By popular demand this version has a several interesting new features:
>
>       * Works with Sesame 2.0 beta 6 without any additional patches (The
>         formerly needed patches for dataset support have been integrated
>         into standard Sesame).
>       * Supports default dataset (no need for FROM clauses in views any
>         more.) Handle with care - this can be resource intensive, as it
>         creates views on your whole repository.
>       * Supports views in the null context. Simply use ng:NullContext as
>         subject of your view definitions.
>       * Does not forbid blank node creation in CONSTRUCT patterns any
>         more. Handle with care - this can lead to infinite models and
>         hence to infinite recursion in the reasoning engine.
>       * Fixes all known bugs as of 2007-10-17
>
> A Sesame repository for testing purposes is available at [4]. [4] is a
> SPARQL and Sesame HTTP endpoint. It can be queried using any SPARQL
> aware tool. You can query, add and modify data using a Sesame2
> HttpRepository or the openrdf-workbench, which you can access at [5].
> The repository contains some test data [6]. You will get the idea of
> networked graphs by executing queries like
> "SELECT * FROM <http://ex.org/graph2> WHERE {?s ?p ?o}"
> with and without including inferred statements. In case anything gets
> broken, simply clear the repository and re-upload the data from [6].
>
> While with this endpoint you still need to collect all neccessary
> graphs before evaluating views, future versions will allow to
> transparently forward (sub-)queries to remote SPARQL endpoints.
>
> Best regards,
> Simon
>
> [1] http://www.openrdf.org
> [2] http://isweb.uni-koblenz.de/Research/NetworkedGraphs
> [3] http://www.uni-koblenz.de/~sschenk/publications/2007/ngtr.pdf
> [4]http://k-
> sems.uni-koblenz.de:8180/openrdf-sesame/repositories/networkedGraphs
> [5] http://k-sems.uni-koblenz.de:8180/openrdf-workbench
> [6] http://www.uni-koblenz.de/~sschenk/software/NGTestGraphs.trig
>
> --
> Simon Schenk | ISWeb | Uni Koblenz-Landau
> http://www.uni-koblenz.de/~sschenk
>
>