# Problem with query federation to Fuseki, missing prefix

**URL:** <https://community.stardog.com/t/problem-with-query-federation-to-fuseki-missing-prefix/3271>\
**Category:** Support\
**Created:** [September 20, 2021, 9:01am UTC](https://community.stardog.com/t/problem-with-query-federation-to-fuseki-missing-prefix/3271 "2021-09-20T09:01:59Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![gcoskun](https://avatars.discourse-cdn.com/v4/letter/g/a587f6/32.png) [@gcoskun](https://community.stardog.com/u/gcoskun)\
**Post date:** [September 20, 2021, 9:01am UTC](https://community.stardog.com/t/problem-with-query-federation-to-fuseki-missing-prefix/3271/1 "2021-09-20T09:01:59Z")

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Hi,

I am running the following query with stardog studio:

```auto
(.........)
  Service ?connectionURI{
      graph ?namedGraphs{
        ?s ?p <https://pid.bayer.com/2000/I/SolubilityResult_45094> ;
        OPTIONAL{?s ?p2 ?o . 
} FILTER (!isLITERAL(?o) || LANG(?o) = "" || LANG(?o) = "en")
}
OPTIONAL{?o2 a ?s}    
} }}

```

the federation part is send to a fuseki server. on the fuseki output I see the following:

```auto
08:55:53 INFO Fuseki :: [143] Query = SELECT ?s ?p ?namedGraphs ?p2 ?o ?o2 WHERE { { GRAPH ?namedGraphs { ?s ?p <https://pid.bayer.com/2000/I/SolubilityResult_45094> . } OPTIONAL { GRAPH ?namedGraphs { ?s ?p2 ?o . } } FILTER ((!(isLiteral(?o)) || ("" = Lang(?o) || "en" = Lang(?o)))) } OPTIONAL { ?o2 rdf:type ?s . } }
08:55:53 INFO Fuseki :: [143] 400 Bad Request (0 ms)

```

I see that "a" was replaced by rdf:type but rdf as a prefix ist not defined. When I copy paste this query to the fuseki UI and add a prefix definition for rdf, the query works. Is it possible that stardog forgets to forward the prefixes for the part within the service element?

Thanks in advance

---

<div class="post-metadata">

**Author:** ![system](https://canada1.discourse-cdn.com/flex030/uploads/stardog/original/2X/e/ed66b48a616f505106a4acde3c9cee7e6da9bc67.svg) [@system](https://community.stardog.com/u/system)\
**Post date:** [October 4, 2021, 9:02am UTC](https://community.stardog.com/t/problem-with-query-federation-to-fuseki-missing-prefix/3271/2 "2021-10-04T09:02:57Z")

</div>

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