Correct querying D2RQ model in Jena

Hello,

I have a trouble with right construction of SPARQl query to D2RQ mapping-file.

I have a table in my db schema:

CREATE TABLE fact (

id integer NOT NULL,

argument1 character varying,

relation character varying,

argument2 character varying,

confidence double precision,

CONSTRAINT facts_pkey PRIMARY KEY (id)

)

And there is only one row:

insert into fact values(1,'conributor','town','Berlin',0.67,4)

And I've generated a mapping between my schema and RDF model via mapping_generation command in D2RQ and get the following .ttl file:

@prefix map: <#> .

@prefix db: <> .

@prefix vocab: <vocab/> .

@prefix rdf: < http://www.w3.org/1999/02/22-rdf-syntax-ns# > .

@prefix rdfs: < http://www.w3.org/2000/01/rdf-schema# > .

@prefix xsd: < http://www.w3.org/2001/XMLSchema# > .

@prefix d2rq: < http://www.wiwiss.fu-berlin.de/suhl/bizer/D2RQ/0.1# > .

@prefix jdbc: < http://d2rq.org/terms/jdbc/ > .

map:database a d2rq:Database;

d2rq:jdbcDriver "org.postgresql.Driver";

d2rq:jdbcDSN "jdbc:postgresql://localhost:5432/postgres";

d2rq:username "postgres";

d2rq:password "password";

map:fact a d2rq:ClassMap;

d2rq:dataStorage map:database;

d2rq:uriPattern "fact/@@fact.id@@";

d2rq:class vocab:fact;

d2rq:classDefinitionLabel "fact";
    .

map:fact__label a d2rq:PropertyBridge;

d2rq:belongsToClassMap map:fact;

d2rq:property rdfs:label;

d2rq:pattern "fact #@@fact.id@@";
.

map:fact_id a d2rq:PropertyBridge;

d2rq:belongsToClassMap map:fact;

d2rq:property vocab:fact_id;

d2rq:propertyDefinitionLabel "fact id";

d2rq:column "fact.id";

d2rq:datatype xsd:integer;
.

map:fact_argument1 a d2rq:PropertyBridge;

d2rq:belongsToClassMap map:fact;

d2rq:property vocab:fact_argument1;

d2rq:propertyDefinitionLabel "fact argument1";

d2rq:column "fact.argument1";
.

map:fact_relation a d2rq:PropertyBridge;

d2rq:belongsToClassMap map:fact;

d2rq:property vocab:fact_relation;

d2rq:propertyDefinitionLabel "fact relation";

d2rq:column "fact.relation";
.

map:fact_argument2 a d2rq:PropertyBridge;

d2rq:belongsToClassMap map:fact;

d2rq:property vocab:fact_argument2;

d2rq:propertyDefinitionLabel "fact argument2";

d2rq:column "fact.argument2";
.

map:fact_confidence a d2rq:PropertyBridge;

d2rq:belongsToClassMap map:fact;

d2rq:property vocab:fact_confidence;

d2rq:propertyDefinitionLabel "fact confidence";

d2rq:column "fact.confidence";

d2rq:datatype xsd:double;
.

My problem is that I don't know how to correctly write sparql query to this model.

How shoud sparql query look like for the following request: get relation1 where relation2 = 'Berlin'

Query, that I constructed, returns empty result:

PREFIX vocab: <vocab/>
SELECT ?name WHERE { ?id vocab: fact_argument2 "Berlin" . ?id vocab:fact _argument1 ?name . }