Crate vowl_wasm 

vowl-wasm — an ontology visualisation engine in Rust, compiled to WebAssembly.

This crate turns an OWL ontology into something a browser can draw: it parses the ontology, builds a typed graph out of it, settles that graph with a force-directed layout, and hands the result to JavaScript. It is a clean-room Rust reimplementation of the VOWL visual notation defined by VisualDataWeb/WebVOWL (MIT, © 2014–2019 Vincent Link, Steffen Lohmann, Eduard Marbach, Stefan Negru, Vitalis Wiens). No upstream JavaScript, fixtures, or assets are vendored here; only the notation and the on-the-wire JSON shape are shared.

The two entry points

WebVowl is the general-purpose surface: load an ontology, run the simulation, read the graph back. It is always available.

NggExplorer is a narrower, allocation-free surface for a rendering worker: it loads a pre-baked binary tier and exposes the live position buffer as a pointer into WASM linear memory, so JavaScript can build a zero-copy Float32Array over it and never pay a per-frame serialisation cost. It requires the ngg1 feature.

Example

Parse a small ontology, settle it, and read the result. This is the same API JavaScript sees, minus the camelCase renaming applied at the WASM boundary.

use vowl_wasm::bindings::WebVowl;

let mut vowl = WebVowl::new();

// WebVOWL-shaped ontology JSON: classes and the properties between them.
vowl.load_ontology(r#"{
    "class": [
        { "id": "c1", "label": "Person",       "type": "owl:Class" },
        { "id": "c2", "label": "Organisation", "type": "owl:Class" }
    ],
    "property": [
        { "id": "p1", "label": "worksFor", "type": "owl:ObjectProperty",
          "domain": "c1", "range": "c2" }
    ]
}"#).expect("valid ontology");

assert_eq!(vowl.get_node_count(), 2);

// Settle the layout: seed the simulation, then anneal it.
vowl.init_simulation().expect("graph is loaded");
vowl.run_simulation(120).expect("graph is loaded");

// Alpha decays as the layout cools.
assert!(vowl.get_alpha() < 1.0);

The JavaScript API

Every method below is exported to JavaScript under the js_name shown. This is the frozen 0.1.0 surface: names and signatures will not change without a major version bump. Later 0.1.x releases only add to it — getNodeIds, getNodePositions and writePositionsInto arrived in 0.1.1.

Reading positions

get_node_positions is the always-available way to get coordinates out after a tick. Node index order is stable for the lifetime of a loaded graph — ticking, pinning, filtering and folding never reorder or remove nodes — so pair it once with get_node_ids and then read only floats per frame:

const ids = vowl.getNodeIds();          // once, after loadOntology
vowl.tick();
const xy = vowl.getNodePositions();     // ids[i] <-> xy[2i], xy[2i + 1]

getGraphData() remains the way to read labels, types and edges, and stays behind debug-serde.

WebVowl — always available

JavaScript	Rust	Purpose
new WebVowl()	WebVowl::new	Construct an empty instance
loadOntology(json)	load_ontology	Parse and build the graph
initSimulation()	init_simulation	Seed the force simulation
runSimulation(n)	run_simulation	Advance n steps
tick()	tick	Advance one step
isFinished()	is_finished	Has the layout settled?
getAlpha()	get_alpha	Annealing temperature
setCenter(x, y)	set_center	Move the layout centre
setLinkDistance(d)	set_link_distance	Spring rest length
setChargeStrength(s)	set_charge_strength	Repulsion strength
getNodeCount()	get_node_count	Node count
getEdgeCount()	get_edge_count	Edge count
getNodeIds()	get_node_ids	Node ids, in index order
getNodePositions()	get_node_positions	Live x, y per node as a Float32Array
writePositionsInto(buf)	write_positions_into	Copy those positions into a caller-owned buffer
getStatistics()	get_statistics	Degree, components, OWL2 metrics
getMetadata()	get_metadata	Ontology header (IRI, version, title)

Filtering, pinning and folding (filterByDegree, toggleDatatypes, toggleSetOperators, resetVisibility, filterHierarchy, pinNode, unpinNode, isPinned, resetPins, getPinnedCount, getNodeDegree) are also always available; see bindings::WebVowl for the full list.

Feature-gated

JavaScript	Feature	Purpose
getGraphData()	debug-serde	Full-graph serde export, for diagnostics
checkNodeClick(origin, dir)	interaction	Ray-sphere node hit testing
new NggExplorer() and its methods	ngg1	Zero-copy worker physics

Features

All optional features are off by default; the general-purpose engine — OWL/JSON parsing, the graph model, force layout (Barnes-Hut quadtree and the CSR simulation), pinning and statistics — is always compiled.

• ngg1 — the NGG1 binary tier format (a re-export of the ontomark-ngg1 codec) and the NggExplorer binding.
• interaction — ray-sphere hit testing for click and selection.
• debug-serde — the legacy full-graph serde export.
• parallel — data-parallel ontology loading via rayon. Native only.
• simd — WASM SIMD128 force accumulation. Needs the simd128 target feature.

Licence

MIT. See LICENSE, which carries both the upstream WebVOWL notice and DreamLab-AI’s.

Modules

bindings

WASM bindings for JavaScript interop

debug

Debug utilities for force-directed layout

graph

Graph data structures and operations

interactioninteraction

Interaction module for ray-sphere intersection and node click detection

layout

Force-directed layout algorithms

ngg1ngg1

NGG1 binary graph-tier format. The implementation lives in ontomark-ngg1; this module re-exports it unchanged so the vowl_wasm::ngg1 path and every public name keep working.

ontology

OWL Ontology parsing and representation

render

Rendering utilities for SVG and Canvas output

Enums

VowlError

Error types that can occur in WebVOWL operations

Functions

init

WASM module entry point, run once when the module is instantiated.

version

The crate version, as reported to JavaScript.

Type Aliases

Result

Result type alias for WebVOWL operations