Glossary · Information modeling

Schema (data)

Also known as: data schema

German: Schema

In information architecture, a schema is a formal definition of data structure, types, fields, constraints and allowed values. Data or documents can be checked against it automatically.

Information architecture
Ontology

In one sentence

A data schema formally defines structure, types, fields, constraints and allowed values; it is the machine-checkable contract behind interfaces.

Example

A JSON Schema for the machine-status interface of a CNC machine requires the field spindleSpeed as a number in rpm between 0 and 24,000.

Explained in context

Context cards connect this term with others to answer one question. Also in British English and German.

How it applies

Integrated systems: A schema turns an interface agreement into something a machine can check. Validate messages against it at the interface so that structural errors are caught early (data validation).
Technical documentation: XML schemas and DTDs, such as those of DITA, define which elements a topic may contain. RDF Schema (RDFS) defines the classes and properties of vocabularies such as iiRDS.
Governance: Changing a schema changes the contract for every consumer, so schemas need versioning and approval under schema governance.
Limits: A schema checks form, not meaning. Two systems can share a schema and still interpret a field differently; see semantic drift.

Schema vs. data model

A data model describes data types, relationships and meaning. A schema is its formal, often technology-specific expression that tools can validate against.

In RDF

A property with a defined domain and range, in Turtle:

@prefix rdf:  <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix xsd:  <http://www.w3.org/2001/XMLSchema#> .
@prefix ex:   <https://example.com/schema#> .

ex:spindleSpeed a rdf:Property ;
  rdfs:domain ex:MachineStatus ;
  rdfs:range xsd:decimal .