Glossary Updates12 new terms added to the glossaries · October 2, 2026, 22:44 CEST
AI TechDocKnowledge

Glossary · Automation software engineering and architecture

Application programming interface (API)

Also known as: API, Programming interface

German: Programmierschnittstelle (API)

In software engineering, an application programming interface (API) is a defined set of functions, data structures, messages or endpoints through which one software component offers services to other components, together with the rules for using them. In industrial automation, APIs connect control software, engineering tools, MES, cloud services and custom applications.

  • Software engineering

In one sentence

An API is a defined set of functions, data structures or endpoints through which a software component offers services to others.

Example

An engineering tool offers a scripting API that lets a build server open a PLC project, import generated code and compile it without manual interaction.

Explained in context

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

How it applies

  • Engineering: An API defines what a component promises to its callers. Stable APIs let teams develop and update components independently; unstable ones couple release cycles.
  • Integration: In plants, APIs appear as function libraries in a controller, REST or OPC UA interfaces on edge devices and SDKs for vision systems or robots. Each has its own versioning and security rules.
  • Documentation: API reference documentation should cover every call with parameters, units, value ranges, return values, errors, preconditions and side effects, plus the Interface version it applies to. Examples and change logs are as important as the reference itself, and deprecated calls should be marked with their Deprecation path.

API vs. protocol

An API describes how software calls a service; a Protocol (communication) describes the messages exchanged over a connection. Many industrial APIs are built on top of a protocol, but an API change does not necessarily change the protocol, and the other way around.

For AI services, see AI API.

By knowledge.aitechdoc.world · Published September 26, 2026 · Last reviewed

Source: AI TechDoc Blog editorial definition, based on software engineering practice (ISO/IEC/IEEE 24765 vocabulary)

Definitions follow the cited standards and specifications. Where a source is a copyrighted publication, such as an ISO, IEC or EN standard, the definition is a close paraphrase, not a verbatim quotation, so as not to infringe copyright. We recommend reading the original publication. The sections “How it applies” are editorial commentary by AI TechDoc Blog and are not part of any standard.

Seen a mistake? Send us a note!