A utility package that allows you to parse SPARQL JSON results in a convenient RDFJS-based datastructure.
For example, the following SPARQL JSON result can be converted as follows:
In:
{
"head": {
"vars": [
"book"
]
},
"results": {
"bindings": [
{ "book": { "type": "uri", "value": "http://example.org/book/book1" } },
{ "book": { "type": "uri", "value": "http://example.org/book/book2" } },
{ "book": { "type": "uri", "value": "http://example.org/book/book3" } },
{ "book": { "type": "uri", "value": "http://example.org/book/book4" } },
{ "book": { "type": "uri", "value": "http://example.org/book/book5" } }
]
}
}
Out:
[
{ '?book': namedNode('http://example.org/book/book1') },
{ '?book': namedNode('http://example.org/book/book2') },
{ '?book': namedNode('http://example.org/book/book3') },
{ '?book': namedNode('http://example.org/book/book4') },
{ '?book': namedNode('http://example.org/book/book5') },
]
Where namedNode
is an RDFJS named node.
This library automatically converts all SPARQL JSON result values to their respective RDFJS type.
import {SparqlJsonParser} from "sparqljson-parse";
const sparqlJsonParser = new SparqlJsonParser();
Optionally, you can provide a settings object to the constructor with optional parameters:
const sparqlJsonParser = new SparqlJsonParser({
dataFactory: dataFactory, // A custom RDFJS datafactory
prefixVariableQuestionMark: true, // If variable names in the output should be prefixed with '?', default is false.
});
sparqlJsonParser.parseJsonBindings({ "book": { "type": "uri", "value": "http://example.org/book/book1" } })
// This will output { '?book': namedNode('http://example.org/book/book1') }
const sparqlJsonresponse = {
"head": {
"vars": [
"book"
]
},
"results": {
"bindings": [
{ "book": { "type": "uri", "value": "http://example.org/book/book1" } }
]
}
};
sparqlJsonParser.parseJsonResults(sparqlJsonresponse);
// This will output [ { '?book': namedNode('http://example.org/book/book1') } ]
const sparqlJsonresponse = {
"head": {},
"boolean": true
};
sparqlJsonParser.parseJsonBoolean(sparqlJsonresponse);
// This will output true
If you have many query results, then a streaming-based approach might be more efficient.
In this case, you can use the sparqlJsonParser.parseJsonResultsStream
method,
which takes a Node readable stream of SPARQL JSON results as a text stream,
and outputs a stream of parsed bindings.
Optionally, you can also retrieve the variables inside the head
as follows by listening to the variables
event:
sparqlJsonParser.parseJsonResultsStream(myStream)
.on('variables', (variables: RDF.Variable[]) => console.log(variables))
.on('data', (bindings: IBindings) => console.log(bindings));
sparqlJsonParser.parseJsonBooleanStream
also takes a stream as input,
but it returns a promise that resolves to a boolean.
This software is written by Ruben Taelman.
This code is released under the MIT license.