@treecg/actor-init-ldes-client

@treecg/actor-init-ldes-client

Metadata harvester for a Linked Data Event Stream.

Install

npm install -g @treecg/actor-init-ldes-client

In order to use it as a library, you can leave out the -g.

How to use it

Usage from the command line

actor-init-ldes-client --parameter ${PARAMETER} ${URL}

Possible parameters:

Parameter	Description	Possible values
pollingInterval	Number of milliseconds before refetching uncacheable fragments	for example: 5000
mimeType	the MIME type of the output	application/ld+json, text/turtle...
context	path to a file with the JSON-LD context you want to use when MIME type is application/ld+json	for example: ./context.jsonld
fromGeneratedAtTime	datetime to filter members that contain a higher prov:generatedAtTime	for example: 2020-01-01T00:00:00
emitMemberOnce	whether to emit a member only once, because collection contains immutable version objects.	true / false

Example commando with parameters:

actor-init-ldes-client --pollingInterval 5000 --mimeType application/ld+json --context context.jsonld --fromGeneratedAtTime 2021-02-03T15:48:12.309Z --emitMemberOnce true https://lodi.ilabt.imec.be/coghent/dmg/objecten

Usage within application

The easiest way to create an engine (with default config) is as follows:

const newEngine = require('@treecg/actor-init-ldes-client').newEngine;

const LDESClient = new newEngine();

With the engine or client created, you can now use it to call te async createReadStream(url, options) method. Here is an example synchronizing with a TREE root node of an Event Stream with polling interval of 5 seconds:

 main()
 
 function main() {
     try {
         let url = "https://lodi.ilabt.imec.be/coghent/dmg/objecten";
         let options = {
             "pollingInterval": 5000, // millis
             "mimeType": "application/ld+json",
             "fromGeneratedAtTime": new Date("2021-02-03T15:46:12.307Z"),
             "emitMemberOnce": true,
             "jsonLdContext": {
                 "@context": [
                     "https://data.vlaanderen.be/doc/applicatieprofiel/cultureel-erfgoed-object/kandidaatstandaard/2020-07-17/context/cultureel-erfgoed-object-ap.jsonld",
                     "https://data.vlaanderen.be/context/persoon-basis.jsonld",
                     "https://brechtvdv.github.io/demo-data/cultureel-erfgoed-event-ap.jsonld",
                     {
                         "dcterms:isVersionOf": {
                             "@type": "@id"
                         },
                         "prov": "http://www.w3.org/ns/prov#"
                     }
                 ]
             }
         };
         let eventstreamSync = LDESClient.createReadStream(url, options);
         eventstreamSync.on('data', (data) => {
             let obj = JSON.parse(data)
             console.log(obj)
         });
         eventstreamSync.on('end', () => {
             console.log("No more data!")
         });
     } catch (e) {
         console.error(e);
     }
 }