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Semantic GraphQL

Semantic GraphQL provides an API to convert any RDF, RDFS and OWL-based ontologies into GraphQL objects.

The library does not deal with data, only with terminology. Therefore resolving data/resources is up to you.

Table of contents:

• Installation
• Getting started
• SemanticGraph API
• Resolvers
• Overriding default values
• Using Relay
• OWL features roadmap
• Contributing
• License

Installation

Runs on Node v6 or higher.

npm install semantic-graphql --save

Getting started

Semantic-graphql makes no assumption about the shape of your data and only passes it around. You have to provide six functions to resolve it in different ways. See the resolvers section.

const resolvers = { /* Choose how to resolve data */ };

Once your resolvers are written you can create a SemanticGraph. In the graph all the triples defining RDF, RDFS and OWL are included by default.

const SemanticGraph = require('semantic-graphql');

const _ = new SemanticGraph(resolvers, config);

Now you can add your own triples. Only statements defining your terminology (classes + properties) will be used, so you shouldn't add your individuals as it will only consume memory.

_.addTriple({
  subject: 'http://foo.com#MyClass',
  predicate: 'http://www.w3.org/1999/02/22-rdf-syntax-ns#type',
  object: 'http://www.w3.org/2002/07/owl#Class',
});

// From a string or a file. Multiple formats are available.
_.parse(string);
_.parseFile('/path/to/ontology.ttl');

When Semantic-graphql translates a rdf:Property to a GraphQLFieldConfig, the resulting type will be wrapped in a GraphQLList unless the property is a owl:FunctionalProperty. Therefore you may have to do some adjustments in order to prevent that. Almost anything can be overriden, see the override section.

// We do not want rdfs:label to resolve arrays
_['http://www.w3.org/2000/01/rdf-schema#label'].isGraphqlList = false;

Now you can start building your GraphQL schema however you want.

const schema = new GraphQLSchema({
  query: new GraphQLObjectType({
    name: 'Query',
    fields: {
      myField: {
        // GraphQL objects are created on demand using the API
        type: _.getObjectType('http://foo.com#MyClass'),
        resolve: /* ... */,
      },
      resource: {
        // The rdfs:Resource interface allows you to query any data
        type: _.getInterfaceType('http://www.w3.org/2000/01/rdf-schema#Resource'),
        args: {
          id: { type: new GraphQLNonNull(GraphQLString) },
        },
        resolve: /* ... */,
      },
    },
  }),
});

Have a look at the examples folder to see a complete setup.

SemanticGraph API

class SemanticGraph {
  constructor(resolvers: Resolvers, config: ?SemanticGraphConfig),
  nTriples: number,
  # The semantic data is stored directly on the graph
  [subject: Iri]: { [predicate: iri]: Array<object: string> },
  # Public methods:
  addTriple: AddTripleFn,
  parse: ParseFn,
  parseFile: ParseFileFn,
  getObjectType: GetObjectTypeFn,
  getInterfaceType: GetInterfaceTypeFn,
  getEdgeType: GetEdgeTypeFn,
  getConnectionType: GetConnectionTypeFn,
  addFieldOnObjectType: AddFieldOnObjectTypeFn,
  extendFieldOnObjectType: ExtendFieldOnObjectTypeFn,
  # When the relay option is on:
  nodeField: GraphQLFieldConfig,
  nodeInterface: GraphQLInterfaceType,
}

type SemanticGraphConfig = {
  prefixes?: PrefixConfig,
  # Activates the Relay features
  relay?: boolean,
  # Your reprefered locale when inferring names and descriptions from rdfs:label and rdfs:comment
  locale?: string = 'en',
  # Prevents the id field to be automatically added to every GraphlQLFieldConfigMap
  preventIdField?: boolean,
}

To prevent GraphQL names collisions, you can edit the name directly (see the override section) or specifify prefixes for ontology namespaces. The names of the generated GraphQL objects will be prefixed. RDF, RDFS and OWL ontologies are by default prefixed with "rdf", "rdfs" and "owl". So a fragment on rdfs:Resource should be "on RdfsResource".

type PrefixConfig = {
  [prefix: string]: Iri,
}

# Must represent a valid IRI
type Iri = string

addTriple

type AddTripleFn(triple: Triple) => undefined

type Triple = {
  subject: Iri,
  predicate: Iri,
  object: Iri | string,
}

Appends a triple to the graph. No-op if the subject or predicate IRI is invalid, or if the triple already exists.

parse

Deprecated

parseFile

Deprecated

getObjectType

type GetObjectTypeFn = (classIri: Iri) => GraphQLObjectType

Returns the GraphQLObjectType corresponding to a given individual of rdfs:Class or its sub-classes (like owl:Class). Throws if the IRI is not found in the graph.

getInterfaceType

type GetInterfaceTypeFn = (classIri: Iri) => GraphQLInterfaceType

getEdgeType

type GetEdgeTypeFn = (classIri: Iri) => ?RelayEdgeType

Returns a value only when the relay: true option is on.

getConnectionType

type GetConnectionTypeFn = (classIri: Iri) => ?RelayConnectionType

Returns a value only when the relay: true option is on.

addFieldOnObjectType

type AddFieldOnObjectTypeFn = (
  classIri: Iri,
  fieldName: string,
  graphqlFieldConfig: GraphQLFieldConfig
) => Iri

Adds a custom field on the GraphQLObjectType and GraphQLInterfaceType representing a class. Throws if "classIri" is not found in the graph. Returns a random IRI referencing the new virtual rdf:Property.

extendFieldOnObjectType

type AddFieldOnObjectTypeFn = (
  classIri: Iri,
  propertyIri: Iri,
  graphqlFieldConfig: PseudoGraphQLFieldConfig
) => undefined

Similar to overriding a field using _['http://foo.com/someProperty'].graphqlFieldConfigExtension = /* ... */ but only for a particular class, not for all of the classes on the property's domain. A PseudoGraphQLFieldConfig is just a GraphQLFieldConfig where every key is optional. The other keys will be infered. Throws if "classIri" is not found in the graph.

Resolvers

Resolvers are functions needed to resolve data. You have to code them.

type Resolvers = {
  resolveSourceId: ResolveSourceIdFn,
  resolveSourceTypes: ResolveSourceTypesFn,
  resolveSourcePropertyValue: ResolveSourcePropertyValueFn,
  resolveResource: ResolveResourceFn,
  resolveResources: ResolveResourcesFn,
  resolveResourcesByPredicate: ResolveResourcesByPredicateFn,
}

type ResolverOutput<x> = x | Array<x> | Promise<x> | Promise<Array<x>>

resolveSourceId

Given a source, resolve its id.

type ResolveSourceIdFn = (
  source?: any,
  context?: any,
  info?: GraphQLResolveInfo
) => ?ID | ?Promise<ID>

Must be sync if you use Relay. See globalIdField's source code

resolveSourceTypes

Given a source, resolve its rdf:type. Can be a single IRI since its super-classes will be infered.

type ResolveSourceTypesFn = (
  source?: any,
  info?: GraphQLResolveInfo
) => ResolverOutput<class: Iri>

resolveSourcePropertyValue

Given a source and the IRI of a predicate, resolve the objects for that source and predicate.

type ResolveSourcePropertyValueFn = (
  source?: any,
  propertyIri?: Iri,
  context?: any,
  info?: GraphQLResolveInfo
) => ?ResolverOutput<any>

resolveResource

Given the IRI of a resource, resolve a "source" for other resolvers to use. You can either return the resource IRI to pass around as source, or fetch all the predicates/objects for that subject and return an object.

type ResolveResourceFn = (
  resourceIri?: Iri,
  context?: any,
  info?: GraphQLResolveInfo
) => ?ResolverOutput<any>

resolveResources

Same as resolveResource but with an array of IRIs.

type ResolveResourcesFn = (
  resourceIris?: Array<Iri>,
  context?: any,
  info?: GraphQLResolveInfo
) => ?ResolverOutput<any>

resolveResourcesByPredicate

Given a array of possible rdf:type, a predicate and an object, resolve the subjects matching that pattern.

type ResolveResourcesByPredicateFn = (
  typeIris?: Array<Iri>,
  predicateIri?: Iri,
  value?: any,
  context?: any,
  info?: GraphQLResolveInfo
) => ?ResolverOutput<any>

Overriding default values

To override anything there is no method: you directly set the library's internals.

_['http://the.resource.to/be#altered'].key = value;

If "key" is already present, the library will use the underlying value and won't try to create it.

Note that the following overrides must be performed before invoking getObjectType or getInterfaceType or getEdgeType or getConnectionType since those methods create the GraphQL objects you want to override.

Examples:

_['http://foo.com#worksForCompany'].graphqlName = 'company';
// Now the field name for foo:worksForCompany will be 'company'

// Partial modifications to fields are achieved using
_['http://foo.com#someOtherProperty'].graphqlFieldConfigExtension = {
  args: /* Look Ma', arguments! */
  resolve: customResolveFn,
};

// Completly overriding a GraphQLObject can be done with
_['http://foo.com/MyClass'].graphqlObjectType = new GraphQLObjectType({ /* ... */});

Using Relay

By using the relay: true option:

• The _.nodeField and _.nodeInterface object are available
• The _.getConnectionType and _.getEdgeType methods are available
• All ObjectTypes exhibit the Node interface
• The id field is a globalIdField

See the Relay example.

OWL features roadmap

• owl:DatatypeProperty
• owl:ObjectProperty
• owl:FunctionalProperty
• owl:inverseOf
• Class expressions (including Restrictions)
• owl:unionOf
• owl:intersectionOf
• owl:complementOf
• owl:equivalentClass
• owl:equivalentProperty
• owl:sameAs
• owl:disjointWith
• owl:differentFrom
• owl:ReflexiveProperty
• owl:SymmetricProperty
• owl:TransitiveProperty
• owl:AsymmetricProperty
• owl:IrreflexiveProperty
• owl:InverseFunctionalProperty

The following features will not be implemented due to their incomptability with GraphQL:

• Some items of the preceding list might be impossible to implement and end up here.

Contributing

Yes, thank you. Please lint, update/write tests and add your name to the package.json file before you PR.

License

Semantic GraphQL is released under the MIT License.

GraphQL is released by Facebook, inc. under the BSD-license with an additional patent grant.