Re: LATERAL: Binding already for ?label (same value)

[Martynas Jusevičius]

How/why is Jena's LATERAL different from the spec? Should I not be relying
on the current implementation?
I am also wondering why VALUES is not used for substitution—was it not
meant as the method for passing bindings to SERVICEs?

The SERVICE wraps a custom ServiceExecutor into an endpoint, so it's not a
Fuseki.
I'm executing the query using the sparql CLI command so the warning
originates from it, not from my code.

A simpler query:

PREFIX worker: <https://example.org/ontology/worker#>
PREFIX wd:     <https://w3id.org/atomgraph/workday#>
PREFIX foaf:   <http://xmlns.com/foaf/0.1/>
PREFIX rdfs:   <http://www.w3.org/2000/01/rdf-schema#>

SELECT *
WHERE {
  ?dgsWorker a worker:87eba76e7f ;
             rdfs:label ?label .

  LATERAL {
    SERVICE <http://localhost:8181/workday/sparql> {
        ?wdWorker a wd:Worker ;
                foaf:name ?label .
    }
  }
}

The queries that the Workday endpoint receives look like this (one for each
?label which is a person's name)

SELECT  ?wdWorker ("John Doe" AS ?label)
WHERE
  { ?wdWorker  a                    <
https://w3id.org/atomgraph/workday#Worker> ;
              <http://xmlns.com/foaf/0.1/name>  "John Doe"
  }


An even simpler query that still prints the same warning:

PREFIX worker: <https://example.org/ontology/worker#>
PREFIX wd:     <https://w3id.org/atomgraph/workday#>
PREFIX foaf:   <http://xmlns.com/foaf/0.1/>
PREFIX rdfs:   <http://www.w3.org/2000/01/rdf-schema#>
PREFIX owl:    <http://www.w3.org/2002/07/owl#>

SELECT *
WHERE {
  ?dgsWorker a worker:87eba76e7f ;
             rdfs:label ?label .

  LATERAL {
    SERVICE <http://localhost:8181/workday/sparql> {
        ?wdWorker a wd:Worker ;
                foaf:name ?label .
    }
  }
}

The query the endpoint receives then looks slightly different:

SELECT  *
WHERE
  { ?wdWorker  a                    <
https://w3id.org/atomgraph/workday#Worker> ;
              <http://xmlns.com/foaf/0.1/name>  "John Doe"
    BIND("John Doe" AS ?label)
  }

On Wed, Mar 11, 2026 at 10:49 AM Andy Seaborne <a...@apache.org> wrote:

> The current LATERAL implementation in Jena does not work the way the
> spec is going.
>
> Jena is rewriting the query (as you can see in the Fuseki log) as
>
>     "SELECT ?wdWorker ("string" AS ?label) {"
>
> which is illegal because  ?label is set in the query pattern.
>
> At a guess, the syntax checker for LATERAL is not looking inside SERVICE
> but I'd also expect the server to reject the query (400), not fail as an
> execution error.
>
> Does that form appear in the fuseki log?
> Any other messages?
>
>  > 14:39:59 WARN  QueryIterCommonParent$ConverterExtend :: Binding
> already for
>  > ?label (same value)
>
> Is that in the Fuseki log or output by the local query execution log?
>
> Do you have a simpler query example?
>
>      Andy
>
> On 09/03/2026 14:02, Martynas Jusevičius wrote:
> > Hi,
> >
> > I found a use case for LATERAL and I'm testing a query like this:
> >
> > PREFIX worker: <https://example.org/ontology/worker#>
> > PREFIX wd:     <https://w3id.org/atomgraph/workday#>
> > PREFIX foaf:   <http://xmlns.com/foaf/0.1/>
> > PREFIX rdfs:   <http://www.w3.org/2000/01/rdf-schema#>
> > PREFIX owl:    <http://www.w3.org/2002/07/owl#>
> >
> > CONSTRUCT {
> >    ?dgsWorker owl:sameAs ?wdWorker .
> > }
> > WHERE {
> >    ?dgsWorker a worker:Person ;
> >               rdfs:label ?label .
> >
> >    LATERAL {
> >      SERVICE <http://localhost:8181/workday/sparql> {
> >        SELECT ?wdWorker ?label {
> >            ?wdWorker a wd:Worker ;
> >                      foaf:name ?label .
> >        }
> >      }
> >    }
> > }
> >
> > It gets names from a local file and reconciles them against a virtual
> > SPARQL endpoint.
> > The query produces results but each SERVICE call prints a warning like
> this:
> >
> > 14:39:59 WARN  QueryIterCommonParent$ConverterExtend :: Binding already
> for
> > ?label (same value)
> >
> > What does this mean exactly? Does the query need reformulation to avoid
> > this?
> >
> > Thanks.
> >
> > Martynas
> >
>
>