GraphQL Directive: @bind

The @bind directive is used to associate a field in your GraphQL query or schema with a SPARQL expression. Note that @pattern is for graph patterns rather than expressions. As bind only produces a single value from the input binding, its cardinality defaults to @one. Explicitly adding @many will cause the value to be wrapped in an array.

Purpose

The directive allows one to compute values for a field based on variables that are mentioned in any ancestor node. The most common use is to expose an entity’s IRI (or blank node) as an id field.

Usage

The @bind directive supports the following arguments:

• of (String): The value of of is a SPARQL expression. The mentioned variables must be defined in any ancestor or at the annotated field.
• as (String): (optional) The variable for the expression result can be specified explicitly (by default an internal name is generated).
• target (Boolean): (optional, defaults to true) Whether the @bind expression produces the target values for the annotated field. If target is false then the field introduces the specified variable that can be referenced from descendants without it becoming a target of the field. Multiple target variables are combined into a tuple based on the order of their appearance.

Example

Here is an example demonstrating how to define a MusicalArtists field using the @bind directive:

{
  MusicalArtists @pattern(of: "?s a <http://dbpedia.org/ontology/MusicalArtist>") {
    id @bind(of: "?s")
  }
}