SPARQL query w/ multiple Accept mime types

Support Bug
1

I am having an issue trying to make a request to the SPARQL query route /{db}/query with multiple Accept mime types.

There is no single Accept mime type on the SPARQL query route which works for all query types, and so it is convenient for me to specify multiple Accept mime types on the request. The reason for this is that I do not necessarily know the SPARQL query type being passed to the route. I chose 3 different Accept mime types for the following query types:

  • CONSTRUCT / DESCRIBE: application/n-quads,
  • SELECT: text/csv,
  • ASK: text/boolean

Format 1

curl --location --request GET '{host}/{db}/query?query={urlEncodedQuery}' \
--header 'Accept: application/n-quads' \
--header 'Accept: text/csv' \
--header 'Accept: text/boolean'

Tests

  • CONSTRUCT Query
    • CONSTRUCT {GRAPH ?g {?s ?p ?o}} WHERE {GRAPH ?g {?s ?p ?o}}
    • Sends back expected result
  • SELECT Query
    • SELECT ?s ?p ?o ?g WHERE {GRAPH ?g {?s ?p ?o}}
    • Sends back expected result
  • ASK Query
    • ASK WHERE {GRAPH ?g {?s ?p ?o}}
    • Error: text/csv is not a known mime type for the results of a query

Format 2

curl --location --request GET '{host}/{db}/query?query={urlEncodedQuery}' \
--header 'Accept: application/n-quads' \
--header 'Accept: text/boolean' \
--header 'Accept: text/csv'
  • Switched --header 'Accept: text/boolean' with --header 'Accept: text/csv'

Tests

  • CONSTRUCT Query
    • CONSTRUCT {GRAPH ?g {?s ?p ?o}} WHERE {GRAPH ?g {?s ?p ?o}}
    • Sends back expected result
  • SELECT Query
    • SELECT ?s ?p ?o ?g WHERE {GRAPH ?g {?s ?p ?o}}
    • Error: text/boolean is not a known mime type for the results of a query
  • ASK Query
    • ASK WHERE {GRAPH ?g {?s ?p ?o}}
    • Sends back expected result

The order of the Accept mime types matters only for ASK and SELECT. No matter where you put the --header 'Accept: application/n-quads' declaration, the CONSTRUCT query will always return the expected result.

2

Solution

You could have the following Accept header and it will work for all query types:

--header 'Accept: application/n-quads, application/sparql-results+xml'

Although this does work, I still wish we could have the ability to specify 3 Accept mime types for the 3 individual SPARQL query types.