RSP.js

An RDF Stream Processing Library for Javascript built on top of N3.js and Comunica

Installation

The library is available on npm. To install it, run the following command:

``
npm i rsp-js
`

Usage

You can define a query using the RSP-QL syntax. An example query is shown below:

`ts
let query = PREFIX :
REGISTER RStream

AS
SELECT *
FROM NAMED WINDOW :w1 ON STREAM :stream1 [RANGE 10 STEP 2]
WHERE{
WINDOW :w1 { ?s ?p ?o}
};
`

You can then create an instance of the RSPEngine and pass the query to it, as shown below:

`ts
let rspEngine = new RSPEngine(query);
`

You can add stream elements to the RSPEngine using the add method. The method takes in a stream element and a timestamp

`ts
stream.add(quad(
namedNode('https://rsp.js/test_subject_'),
namedNode('http://rsp.js/test_property'),
namedNode('http://rsp.js/test_object'),
defaultGraph(),
), timestamp_value);
`

In the following example, we will use a function generate_data to mock the stream.

`ts
import { RSPEngine, RDFStream } from "rsp4js";

async function RSP() {
let query = PREFIX :
REGISTER RStream

AS
SELECT *
FROM NAMED WINDOW :w1 ON STREAM :stream1 [RANGE 10 STEP 2]
WHERE{
WINDOW :w1 { ?s ?p ?o}
};

let rspEngine = new RSPEngine(query);
let stream = rspEngine.getStream("https://rsp.js/stream1");
let emitter = rspEngine.register();
let results = new Array();
emitter.on("RStream", (object: any) => {
console.log("received results");
results.push(object.bindings.toString());
});
if (stream) {
generate_data(10, [stream]);
}
console.log(results);
}

RSP();
`

`ts
const N3 = require("n3");
const { DataFactory } = N3;
const { namedNode, defaultGraph, quad } = DataFactory;

async function generate_data(num_events: number, rdfStreams: RDFStream[]) {
for (let i = 0; i < num_events; i++) {
rdfStreams.forEach((stream: any) => {
const stream_element = quad(
namedNode("https://rsp.js/test_subject_" + i),
namedNode("http://rsp.js/test_property"),
namedNode("http://rsp.js/test_object"),
defaultGraph()
);
stream.add(stream_element, i);
});
}
}
``

Current Features:

- RSP-QL support
- Support multiple windows
- Support for stream and static data joins