What is Ontology?

Without an ontology, integrating data means mapping each system to every other one by hand, and the mappings break whenever a source system changes. An ontology gives the business one stable vocabulary that does not depend on how any single system stores its data.

When teams, departments or partner organisations agree on an ontology, they can share and combine data without building a separate integration for every pair of systems. In regulated industries, where terms have to be used consistently, that agreement is often a requirement in itself.

An ontology also lets software draw conclusions. If it states that paracetamol is an analgesic and that analgesics treat pain, a reasoner can conclude that paracetamol treats pain, although nobody wrote that down.

Ontologies are usually written in OWL (Web Ontology Language) or RDFS (RDF Schema). They are made of:

Classes. The kinds of things in the domain, such as Person, Organisation or Product.

Properties. Attributes and relationships, such as hasName, worksFor or partOf.

Constraints. Rules about the data, such as cardinality (a Person has exactly one date of birth) or domain and range (worksFor links a Person to an Organisation).

Ontology engineering is the work of designing, testing and maintaining these models. Domain experts, data architects and ontology engineers do it together, because the model has to be accurate about the domain and still practical to use.

FIBO. The Financial Industry Business Ontology is an open standard for financial services, covering legal entities, instruments and regulatory concepts. Banks use it to describe data the same way across trading, risk and compliance systems.

Schema.org. A lightweight vocabulary that millions of websites use to mark up their pages for search engines. The rich results in Google, such as star ratings and event dates, mostly come from Schema.org markup.

Product catalogues. A manufacturer can classify its whole product range in one ontology shared across divisions, so search, cross-selling and regulatory reporting all use the same product categories.