SPARQL functions in CONSTRUCT/WHERE

I mostly use SPARQL SELECT while working on a query for debugging purposes but in the end I want to use the final result it in a CONSTRUCT way; as I want to work with a graph and not key/value query results.

What I don't get yet (and can't seem to find with search engines/docs) is if I can use functions as well that way. As an example, I use a property path to concatenate titles I get into a "superstring", which I later use for building a Lucene index to increase plain text search quality:

PREFIX dc: <http://purl.org/dc/elements/1.1/>    

SELECT (group_concat(?title ; separator = " ") AS ?fancytitle) WHERE { 
  GRAPH ?graph {
    <http://data.staatsarchiv-bs.ch/id/archivalresource/CH-000027-1/pa-633c-a-312-fasc-163>  dc:relation+ ?relation .
    ?relation dc:title ?title .
  }
}

Now I would like to have the same ?fancytitleas a new triple like

<http://data.staatsarchiv-bs.ch/id/archivalresource/CH-000027-1/pa-633c-a-312-fasc-163> <fancytitle> ?fancytitle .

So I can store it directly in a new graph. Is this possible? I played with some queries but couldn't manage to get it accepted by the SPARQL processor. FYI I'm using Fuseki.

You can try it out at my SPARQL Endpoint

Yes this is possible

You can't use expressions directly in a CONSTRUCT template but you can assign the variable in the WHERE clause either via a SELECT expression in a sub-query or using BIND.

In your case as GROUP_CONCAT is an aggregate it can only be a SELECT expression so you just need to put your entire SELECT as a sub-query e.g.

PREFIX dc: <http://purl.org/dc/elements/1.1/>    

CONSTRUCT
{
  <http://data.staatsarchiv-bs.ch/id/archivalresource/CH-000027-1/pa-633c-a-312-fasc-163> <http://fancyTitle> ?fancytitle
}
WHERE
{
  SELECT (group_concat(?title ; separator = " ") AS ?fancytitle) WHERE { 
    GRAPH ?graph {
      <http://data.staatsarchiv-bs.ch/id/archivalresource/CH-000027-1/pa-633c-a-312-fasc-163>  dc:relation+ ?relation .
      ?relation dc:title ?title .
    }
  }
}

The above works fine on your endpoint

With the help of my colleague we got it to work, UNION and GROUP BY are essential. This query puts the string together for all locah:ArchivalResource in the graphs:

CONSTRUCT
{
  ?archresource skos:hiddenLabel ?supertitle
}
WHERE
{
  SELECT ?archresource  (group_concat(?title ; separator = ", ") AS ?supertitle) WHERE {
    GRAPH ?graph {
      {
        SELECT ?title ?archresource WHERE {
          GRAPH ?graph {
            {
              ?archresource a locah:ArchivalResource ;
              dc:title ?title .
            } UNION
            {
              ?archresource dc:relation+ ?relation .
              ?relation dc:title ?title .
            }
          }
        }
      }
    }
  } GROUP BY ?archresource
}