Short definition

A development approach in which a business ontology, extracted from the code and then kept up against it, serves as the reference for framing, checking and judging the changes an AI agent makes to a piece of software.

Full definition

The term predates this blog. In 2005 Pavel Hruby described an approach called Ontology-Based Domain-Driven Design, and work such as ODDToolkit has explored generating software artefacts from formal ontologies. In those uses, the ontology comes first and the software follows from it.

In the articles on this blog, the meaning is different. The ontology is not an imposed formalism — neither OWL nor RDF — but a plain-language file, ontology.md, extracted from the code by Claude Code. It is not used to generate the software: it serves as a shared reference for consistency for the agents that modify it. The approach is organised around three points — before development, hold the request up against the model; during and after, detect drift from the changes in the repository; before integration, produce a consistency report — and it settles each gap by setting the intent, the code and the ontology against each other.

Usage in the field

Development assisted by coding agents, building tooling around Claude Code (hooks, Git analysis scripts), maintaining the business language of an ERP or business management software.

Synonyms and variants

ODD.

Not to be confused with

• TDD — an approach where a test written before the code pins down a behaviour deterministically; ODD borrows its order of operations without having its guarantee.
• Domain-Driven Design — a set of principles for modelling a domain (ubiquitous language, bounded contexts); ODD adds an operational mechanism for continuous checking.
• Ontology — the artefact the approach relies on, not the approach itself.

Examples

In a fictional ERP, the request "allow an order without a quote" is held up against the rule "every order originates from a quote" before any file is modified, and the ontology then changes because the intent called for it.

Ambiguities / debates

The acronym ODD is already used for approaches that generate software from a formal ontology. The meaning used here is an experimental, personal approach, not yet validated on real software changes.