changeset-sparql

Applies a changeset via SPARQL Update

npm install changeset-sparql

Usage:

First we make a changeset:

const EX = 'http://example.info/'
const changeset = {
    // an array of triples/quads to add
     add: [{s: EX+'123', p: EX+'count', o_value: 0, o_type:'literal', o_datatype: EX+'integer', g: EX+'graphs/graph-name'}]
    // triples/quads to remove (changeset will fail if they don't exist)
   , remove: [{s: EX+'987', p: EX+'message',  o_value: "Hello", o_type:'literal', o_lang: 'en-gb'}]
    // the URIs of the latest changesets for each subject we want to change
   , previous: ["urn:hash:sha1:jkhjkhkj2kjh3", "urn:hash:sha1:mnwejkljh7898c"],

}

Now we define two functions, one to do SPARQL queries, and one to do SPARQL updates.

Each function should take two arguments: a query/update and a "Node-style" ((err, data)=>) callback

const request = require('request')

const endpoint = 'http://localhost:3030/TestData'

const query = (q, callback) => request({
    url: endpoint+'/sparql',
    body: q,
    method: 'POST',
    headers: {
        'Accept': 'application/sparql-results+json',
        'Content-type': 'application/sparql-query'
    }
}, (err, data)=> err? callback(err) : callback(null, JSON.parse(data.body)))

const update = (q, callback) => request({
    url: endpoint+'/update',
    body: q,
    method: 'POST',
    headers: {
        'Accept': 'application/sparql-results+json',
        'Content-type': 'application/sparql-update'
    }
}, callback)

Now we pass those functions to changsetSparql, and get back a function that accepts a changeset, and a dictionary of callbacks:

const changsetSparql = require('changeset-sparql')(query, update)

changsetSparql(changeset, {
    error: console.error,
    rejected: console.error,
    ok: console.log
})

• error Gets called with an error if there are problems running the updates or queries (ie: if query or update call the callback with an error). You may want to retry if this happens.
• rejected gets called with an error message if the changeset was rejected. This happens if:
  • the subject and predicate of a create triple/quad already exists in the dataset
  • any delete triples/quads don't exist in the dataset. You should not retry, but you may want to alter the changeset and resubmit.
• ok Gets called with the URI of the changeset if:
  • The update was successfully applied
  • The changeset was already applied

Changeset Object Specification

• add: optional, must be an Array of quads to be added to the dataset
• remove: optional, must be an Array of quads to be removed from the dataset
• previous: optional, must be an Array of URIs of latest changesets of each subject

Triple/Quad Specification

(format of the objects in the add and remove Arrays)

• s: required, URI (subject)
• p: required, URI (predicate/property)
• o_value: required (object value)
• o_type: required, must be uri OR literal
• o_lang: optional, must be valid language tag
• o_datatype: optional, URI
• g: optional, URI (graph)