Glossary · Automation fundamentals, platforms and components
JSON
Also known as: JavaScript Object Notation
German: JSON
In data exchange, JSON (JavaScript Object Notation) is a lightweight text format for structured data made of objects (name/value pairs), arrays, strings, numbers, booleans and null. It is specified in RFC 8259 and ECMA-404.
- Automation components
- Standards
In one sentence
JSON is a lightweight text format for structured data with objects, arrays and values, specified in RFC 8259 and ECMA-404.
Example
A machine publishes {"state":"Execute","goodCount":1520} as a JSON message to an MQTT broker every second.
Explained in context
Context cards connect this term with others to answer one question. Also in British English and German.
How it applies
- Engineering: JSON is the common payload format for REST APIs, MQTT messages and configuration files. JSON Schema is used to describe and validate structures.
- Integration: JSON has no built-in units or semantics; names and meanings must be agreed separately, for example through a Schema (data) or an information model.
- Documentation: Document message structures with examples and schemas, including units, value ranges and optional fields. Version the schemas and describe changes in release notes.
- Maintenance: Validating incoming JSON against a schema helps detect faulty messages early instead of storing wrong data.
JSON vs. JSON-LD
JSON-LD is JSON with linked data context, so names map to globally defined terms (IRIs). It is used for structured data on websites and knowledge graphs. Plain JSON leaves the meaning to documentation and convention.