A JSON-LD Context
for the query. In an API, this will frequently be implicit. For example,
using json-rql as the body of a POST
to
http://example.com/my-api/v1/person/query
might have the implicit context
of a Person (possibly found at http://example.com/my-api/v1/person
).
A declaration of the selection of variables that will be returned.
The data pattern to match, as a set of subjects or a group. Variables are used as placeholders to capture matching properties and values in the domain.
Examples:
Match a subject by its @id
{
...
"@where": { "@id": "fred" }
}
Match a subject where any property has a given value
{
...
"@where": {
"@id": "?id",
"?prop": "Bedrock"
}
}
Match a subject with a given property, having any value
{
...
"@where": {
"@id": "?id",
"name": "?name"
}
}
The Javascript engine supports exact-matches for subject identities, properties and values. Inline filters will be available in future.
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A query pattern that returns values for variables in the query.
The subjects streamed in the query result will have the form:
{ "?var1": <value> "?var2": <value> ... }
Examples:
Select the ids of subjects having a given name
{ "@select": "?id", "@where": { "@id": "?id", "name": "Wilma" } }
Select the ids and names of all subjects
{ "@select": ["?id", "?value"], "@where": { "@id": "?id", "name": "?value" } }
See the
@where
property for more examples of how to use a where clause.https://json-rql.org/interfaces/select.html