OO-LD Reference Schemas¶

Structure travels well. A CSV, a JSON file or a Parquet table opens anywhere, and two labs can exchange files all day without either of them learning anything about the other's data.

Meaning does not travel. The same quantity, process or dataset is modelled differently by every ontology, every schema language and every information system, and the differences are rarely disagreements about the science. They are disagreements about representation: whether a value and its unit sit on one node or two, whether a duration is a quantity or a temporal region, whether a unit is a class or an individual.

The usual response is to pick an ontology. That works inside one project and fails at its boundary, because picking one excludes everyone aligned with another. The boundary is often a domain boundary: a measured quantity crosses from a laboratory to an engineering calculation to a product declaration, and each side has its own vocabulary for the same number. Ontology alignment is supposed to fix that afterwards, but alignment between whole ontologies is a research problem, while the practical need is much smaller: make this schema readable by those communities.

One document, two standards¶

An OO-LD document is at once a valid JSON Schema and a referenceable JSON-LD context. Nothing new is invented; two existing standards are put in one file.

That single move has an outsized effect. The same artefact validates an instance, generates typed code and a form, and expands that instance to RDF. There is no separate context to keep in sync, no generated copy that drifts, and no build step between the developer's view and the semantic view. A developer who never says the word "ontology" still produces linked data.

One syntax, several readings¶

Where communities genuinely differ, a schema here does not pick a winner. The default context carries the reading its module takes as agreed, every further community mapping rides along as a per-term synonym, and selecting a mapping set promotes those synonyms so the same instance document exports as EMMO-flavoured or PMDco-flavoured RDF. Nothing about the instance changes, only its RDF reading. Terms a community has no term for keep the consensus reading rather than failing, so a partial alignment stays usable.

Because the synonyms carry SSSOM metadata, the mappings round-trip to a standard mapping set: they can be reviewed, cited and reused by people who never open a JSON Schema.

Walk through a worked example How the mapping works

What is here¶

Schemas are grouped into modules, each versioned and conformable on its own, so a consumer in civil engineering, manufacturing or trade can adopt quantities without taking on anything domain-specific. Domain modules sit on top of neutral ones rather than replacing them. See Modules for the full set and their status.

Each schema is published at a versioned, dereferenceable path, so a conformance IRI resolves to the schema itself rather than only to a page about it:

https://w3id.org/oo-ld/schemas/quantities/1.0
  -> https://schemas.oo-ld.org/quantities/1.0/QuantityValue.schema.json

Because structure and semantics sit in one document, the schemas are also the source for generated assets: typed code bindings, schema-driven user interfaces, API descriptions, and the SSSOM mapping sets themselves.

What this is not¶

It is not an ontology, and it does not compete with one. Ontologies define what things are, with far more expressivity than a schema can carry. These schemas describe how data is shaped and which ontology terms that shape corresponds to, in the subset that survives a round-trip through ordinary tooling. Where an ontology's structure cannot be reached by term mapping, that is stated plainly rather than papered over.

Status¶

First draft, put up for discussion rather than settled. The module structure is drawn wide enough to give every recurring pattern a home, but which modules exist, what belongs in each and how their terms are mapped are all open. quantities is the worked example; the other modules carry a scope note and are open for contribution, in any domain that shares the pattern.

Everything published here is checked in CI: schemas against the OO-LD meta-schema, instances against their schemas, and every mapping-set reading for a lossless round-trip through RDF.