Wasm Tree
This package is an implementation of RDF.JS Dataset and RDF.JS Store that
resorts to Web Assembly to store the quads in the form of several BTrees of
numbers (unsigned int
on 32 bits).
Correspondance between numbers and actual terms is done in Javascript.
Quick example in Node.js
// Import wasmtree
const wasmtree = require('@bruju/wasm-tree');
// Import other rdf libraries as wasm tree doesn't provide any RDF.JS data model
const rdf = require('@graphy/core.data.factory');
const namespace = require('@rdfjs/namespace');
const ex = namespace('http://example.org/', rdf);
// Populate a dataset
let dataset = new wasmtree.Dataset();
dataset.add(rdf.quad(ex.subject, ex.predicate, ex.object));
dataset.add(rdf.quad(ex.subject, ex.predicate, ex.otherobject));
dataset.add(rdf.quad(ex.other , ex.predicate, ex.object));
// Count number of quads with the object ex.object
const occObjectInObject = dataset.match(null, null, ex.object).size;
console.log(occObjectInObject + " quads have " + ex.object.value + " in object position");
// Free the Web Assembly linear memory
dataset.free();
You can run this example by writing the code in a file named example.js
and then run :
$ npm install @bruju/wasm-tree @graphy/core.data.factory @rdfjs/namespace
$ node example.js
2 quads have http://example.org/object in object position
How to instanciate a dataset or a store
const wasmtree = require('@bruju/wasm-tree');
let dataset = new wasmtree.Dataset();
let store = new wasmtree.Store();
Dataset
The DatasetCore and most Dataset features from RDF.JS are implemented
https://rdf.js.org/dataset-spec/
We currently do not implement import
, toStream
, toString
and toCanonical
.
Also note that the equals function does not normalize the black node as specified.
Store
The Store interface from RDF.JS is fully implemented
http://rdf.js.org/stream-spec/
add(quad: RDF.Quad): void
and addQuad(quad: RDF.Quad): void
are also provided to help synchronously populate the store.
You can also use the storeStream function
const myStore = wasmtree.storeStream(aStreamOfQuads);
which has a similar behaviour as the npm package RDF Store Stream.
About memory
As Web Assembly doesn't provide a garbage collector, the dataset and the store will keep memory until it is explicitely freed.
const wasmtree = require('@bruju/wasm-tree');
let dataset = new wasmtree.Dataset();
let store = new wasmtree.Store();
// Do some interesting work
dataset.free();
store.free();
The free function will deallocate the memory, and empty the structures. If a freed variable is reused, it will allocate again some web assembly memory.
Note that some dataset built from other dataset calls do not necessarily have
to be freed (but still can). For example, dataset.match()
will not allocate
memory from web assembly until a complex operation like adding a quad is
required (looping on the dataset does not trigger the allocation process).
License
Licensied under the MIT License
This has been funded by the REPID Project.