WebAssembly Guide¶

Browser bindings ship as @ontologos/wasm on npm. Shared logic lives in ontologos-js; the WASM crate is a thin wasm-bindgen wrapper. The .wasm module is also on Wasmer as eddiethedean/ontologos.

Install¶

npm install @ontologos/wasm

Channel	How
npm	`@ontologos/wasm` — JS glue + `.wasm`
Wasmer	wasmer.io/eddiethedean/ontologos — `.wasm` module 1.1.4
Source	Build with wasm-pack (below)

Note: The first @ontologos/wasm@1.1.4 npm tarball omitted pkg/ (wasm-pack pkg/.gitignore). Prefer a source build or Wasmer for the .wasm binary until a corrected release ships. For Node, use ontologos on npm.

Build¶

# Install wasm-pack: https://rustwasm.github.io/wasm-pack/installer/
cd crates/ontologos-wasm
npm install
npm run build   # wasm-pack build --target web --out-dir pkg
npm test

The release artifact is large when DL support is included — expect multi‑MB .wasm files. EL/RL-only browser builds may be slimmed in a future release.

Registries¶

On each v*.*.* tag (or via Publish npm / Publish Wasmer workflows), CI publishes:

npm @ontologos/wasm — see npmjs.com/package/@ontologos/wasm
Wasmer eddiethedean/ontologos — see wasmer.toml

The Wasmer package is a wasm-bindgen module (abi = "none"), not a WASI CLI — use it with the JS glue from @ontologos/wasm, not wasmer run alone.

Browser usage¶

import init, { OntologyBuilder, Reasoner } from "@ontologos/wasm";

// Fetch or import the .wasm bytes, then initialize once:
await init({ module_or_path: "/path/to/ontologos_wasm_bg.wasm" });

const builder = new OntologyBuilder();
builder.addClass("http://example.org/Pizza");
builder.addClass("http://example.org/Food");
builder.subclassOf("http://example.org/Pizza", "http://example.org/Food");
const ontology = builder.build();

const reasoner = new Reasoner(ontology, "el");
const report = reasoner.classify();
console.log(report.status, report.subsumption_count);

Bundlers (Vite, webpack, etc.) usually resolve the wasm asset — follow your bundler's wasm-bindgen integration docs.

No filesystem¶

WASM has no file API. Load ontologies from:

Ontology.fromBytes(Uint8Array) — strict parse (default for uploads)
Ontology.fromBytesLenient — trusted corpora only
Ontology.fromText(string) / fromTextLenient
Ontology.fromJson, fromObject, or fromJsonWithLimits / fromObjectWithLimits

Resource limits¶

import { Ontology } from "@ontologos/wasm";

const ontology = Ontology.fromJsonWithLimits(json, 1_048_576);

Recommended browser upload caps: 1–4 MiB JSON or OWL text unless you control memory budgets.

Errors¶

WASM throws Error subclasses with .name and .code set to ParseError, ResourceLimitError, or IncompleteReasoningError:

try {
  Ontology.fromJson("{");
} catch (err) {
  console.log(err.name); // "ParseError"
}

Threading and performance¶

Bindings are single-threaded (Rc<RefCell>). One WASM instance per tab/worker; do not share handles across workers.
DL classification can block the browser main thread. Pass budgetSecs to Reasoner and run heavy DL jobs in a Web Worker with a dedicated WASM instance.
Remote owl:imports are not fetched in WASM (horned-owl remote feature disabled for wasm32).

Security¶

See Security — JavaScript bindings. Default byte/text loaders use strict parse limits.

API surface¶

Mirrors Node/Python: Ontology, OntologyBuilder, Reasoner with classify(), checkConsistency(), isEntailed(), query(), and incremental edits.