Bridges between GraphQL and RDF

Finding a human by id with GraphQL

GraphQL Query:

{
  human(id: "1000") {
    name
    height
  }
}
          

JSON results:

{
  "data": {
    "human": {
      "name": "Luke Skywalker",
      "height": 1.72
    }
  }
}
          

Finding a human by URI with SPARQL

GraphQL Query:

@prefix schema: <https://schema.org/>.
SELECT ?name ?height WHERE {
  <http//example.org/human/1000> a schema:Person;
                                   schema:name ?name;
                                   schema:height ?height.
}
          

JSON results:

{
  "head": {
    "vars": [ "name" , "height" ]
  },
  "results": {
    "bindings": [
      {
        "name": { "type": "literal" , "value": "Luke Skywalker" },
        "height": { "type": "literal" , "value": "1.72", "datatype": "http://www.w3.org/2001/XMLSchema#double" },
      }
    ]
  }
}
          

GraphQL vs SPARQL

Using GraphQL to query RDF:
different approaches exist

• GraphQL-LD: Conversion to SPARQL based on a JSON-LD context,
  independent of any engine and works for any RDF source.
• Stardog: SPARQL engine that also accepts GraphQL (converted to SPARQL). Conversion is done using a GraphQL schema, or @prefix directives.
• HyperGraphQL: GraphQL interface wrapper around RDF sources using a configuration file and an annotated GraphQL schema.
• TopBraid: Graph store with GraphQL interface. GraphQL schemas can be generated using shape definitions (SHACL).

These approaches are incompatible

{
  human {
    name
    height
  }
}
          

{
  Human {
    name
    height
  }
}
          

SELECT ?name ?height WHERE {
  _:b1 ex:human _:human.
  _:human ex:name ?name;
          ex:height ?height.
}
          

SELECT ?name ?height WHERE {
  _:b1 a ex:Human;
       ex:name ?name;
       ex:height ?height.
}
          

More differences

• Aggregates (sum, count, ...)
• Filtering (directives, custom fields, ...)
• Optional fields
• Named graphs
• Ordering
• Pagination
• ...

→ Annoying for developers if they want to switch between different approaches

A standard way of querying
RDF with GraphQL is needed

Proposal for a plan of action:

1. Analyze the different aspects of querying RDF with GraphQL.
   (Property paths, joins, ordering, aggregation, ...)
2. Categorize the existing approaches over these aspects.
3. Compare the advantages and disadvantages of each aspect approach.
4. Propose a standard approach and semantics for querying RDF with GraphQL.