[Virtuoso-users] How to make DESCRIBE pragma preferences the default for your Virtuoso instance

[Kingsley Idehen]

Excerpt from a private exchange re., the above that I am making public, due to its importance.

Read on...

On 5/14/14 6:07 AM, Jesús Redondo wrote:

Issue: given the underspecification of SPARQL DESCRIBE, and the plethora of pragmas that Virtuoso offers re., DESCRIBE, how to I make my preference the default for a my Virtuoso instance(s)?

On Fri, May 9, 2014 at 3:31 PM, Kingsley Idehen <kide...@openlinksw.com <mailto:kide...@openlinksw.com>> wrote:

    On 5/9/14 7:48 AM, Jesús Redondo wrote:

    Hello,

    I have the same problem. I have a SPARQL Endpoint:
    http://opendata.caceres.es/sparql and there are resources that
    are described in more than one graph.

    For instance:

    
http://opendata.caceres.es/recurso/urbanismo-infraestructuras/vias/Via/avda_3425

    Get these outputs depending on the Describe query:

    *1)* With the default describe I get these triples:
    Query:
    describe
    
<http://opendata.caceres.es/recurso/urbanismo-infraestructuras/vias/Via/avda_3425>

    Output:
    
http://opendata.caceres.es/sparql?default-graph-uri=&query=describe+%3Chttp%3A%2F%2Fopendata.caceres.es%2Frecurso%2Furbanismo-infraestructuras%2Fvias%2FVia%2Favda_3425%3E&format=text%2Fx-html%2Btr&timeout=0&debug=on

    *2)* With the CBD (sql:describe-mode "CBD) I get these triples:
    Query:
    /DEFINE sql:describe-mode "CBD"
    describe
    
<http://opendata.caceres.es/recurso/urbanismo-infraestructuras/vias/Via/avda_3425>/

    Output:
    
http://opendata.caceres.es/sparql?default-graph-uri=&query=DEFINE+sql%3Adescribe-mode+%22CBD%22%0D%0Adescribe+%3Chttp%3A%2F%2Fopendata.caceres.es%2Frecurso%2Furbanismo-infraestructuras%2Fvias%2FVia%2Favda_3425%3E&format=text%2Fx-html%2Btr&timeout=0&debug=on


    *3)* When I use an ordinary describe with "FROM GRAPH" I get
    these triples:
    Query:
    describe
    
<http://opendata.caceres.es/recurso/urbanismo-infraestructuras/vias/Via/avda_3425>
    FROM NAMED
    <http://opendata.caceres.es/recurso/urbanismo-infraestructuras/vias/Via/>
    FROM NAMED
    
<http://opendata.caceres.es/recurso/transporte/plazas/PlazaMovilidadReducida/>

    Output:
    
http://opendata.caceres.es/sparql?default-graph-uri=&query=describe+%3Chttp%3A%2F%2Fopendata.caceres.es%2Frecurso%2Furbanismo-infraestructuras%2Fvias%2FVia%2Favda_3425%3E%0D%0AFROM+NAMED+%3Chttp%3A%2F%2Fopendata.caceres.es%2Frecurso%2Furbanismo-infraestructuras%2Fvias%2FVia%2F%3E%0D%0AFROM+NAMED+%3Chttp%3A%2F%2Fopendata.caceres.es%2Frecurso%2Ftransporte%2Fplazas%2FPlazaMovilidadReducida%2F%3E&format=text%2Fx-html%2Btr&timeout=0&debug=on

    This third output is the one I am interested in. _The problem is
    that I am using pubby[1] to make the URI of the resources
    resolvable, so I cannot include the "FROM GRAPH" clauses._ I mean
    there is no way I can modify the Query that runs internally, so...

    *Is there a way to force describe to fetch from all the Graphs
    using the default mode?*


    If that were not possible, then as a "lesser evil"...
    *Is there a way to force virtuoso to CBD mode for all describe
    queries?*

    Thanks

    Jesús

    Clearly missing from our online docs is the following:

    You can place any 'define pragma' configuration options in
    SH_DEFINES field of appropriate row of DB.DBA.SYS_SPARQL_HOST
    table . Basically, this is how you achieve your goal.

    BTW -- can I have this response shared with the public Virtuoso
    list, as I suspect others are encountering this problem .

    Table Definition:

    create table "DB"."DBA"."SYS_SPARQL_HOST"
    (
      "SH_HOST" VARCHAR,
      "SH_GRAPH_URI" VARCHAR,
      "SH_USER_URI" VARCHAR,
      "SH_DEFINES" LONG VARCHAR,
      "SH_BASE_URI" VARCHAR,
      PRIMARY KEY ("SH_HOST")
    );


    Query from one of my instances:
    SELECT SH_HOST,SH_GRAPH_URI,SH_USER_URI,SH_DEFINES,SH_BASE_URI
    FROM DB.DBA.SYS_SPARQL_HOST

    Result

SH_HOST VARCHAR SH_GRAPH_URI VARCHAR SH_USER_URI VARCHAR SH_DEFINES LONG VARCHAR SH_BASE_URI VARCHAR * <DB NULL> <DB NULL> define sql:gs-app-callback "ODS" <DB NULL>

--

Regards,

Kingsley Idehen 
Founder & CEO
OpenLink Software
Company Web: http://www.openlinksw.com
Personal Weblog: http://www.openlinksw.com/blog/~kidehen
Twitter Profile: https://twitter.com/kidehen
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LinkedIn Profile: http://www.linkedin.com/in/kidehen

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