# API

> An API (application programming interface) is a defined set of functions and rules that lets one piece of software use the features or data of another system or service.

Original page: https://t10.de/en/glossary/api
Publisher: total10 GmbH, https://t10.de/en/glossary

The international standard ISO/IEC/IEEE 26514:2022 defines an API as a set of functions, protocols, parameters and objects for building software that works with an external system or service. The Gabler Banklexikon, a German banking dictionary, puts it more practically: an API makes a program's functions accessible to other systems and is the prerequisite for linking them by machine.

Germany's Federal Office for Information Security (BSI) notes that web service interfaces are often built with REST (Representational State Transfer) or an alternative called SOAP. Its IT baseline protection guidance (IT-Grundschutz, module APP.3.1) covers how clients prove their identity before accessing protected resources. Roy T. Fielding set out REST in his 2000 [doctoral dissertation](https://ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm) as an architectural style rather than a protocol or standard. At its centre is the resource, any information that can be named; what sets REST apart is a uniform interface between components.

In our projects, an API or SFTP links our bespoke software to SAP, other ERP systems or a warehouse management system, which stay unchanged. Some of our applications have their own API, protected by an access token; on a knowledge platform we built for a pharmaceutical logistics provider, for example, other programs and AI agents use it. In one shop project, a REST API passes documents such as data sheets and certificates to external systems.

## See also

- [Interface](https://t10.de/en/glossary/interface): An interface is the point at which two systems, programs or components meet and exchange data; the word also covers the user interface between a person and software.
- [SFTP](https://t10.de/en/glossary/sftp): SFTP (SSH File Transfer Protocol) transfers files securely over a Secure Shell (SSH) connection; despite the name, it is a separate protocol from the older FTP.
- [Business application](https://t10.de/en/glossary/business-application): In general terms, a business application is software used to perform or support business functions.
- [WMS](https://t10.de/en/glossary/wms): WMS stands for warehouse management system; according to the short description of VDI 3601, its task is to manage and optimise a company's internal storage and transport systems.

## Where the term appears

- [Bespoke software & business apps with Symfony](https://t10.de/en/symfony-development)
- [Pharma IT services: Non-GxP software](https://t10.de/en/pharma)
- [Custom AI agents for businesses](https://t10.de/en/ai-agents)
- [One QR code on every appliance: from EU obligation to service portal](https://t10.de/en/blog/eu-energy-label-qr-platform)
- [The self-driving content machine](https://t10.de/en/blog/self-driving-content-machine)
- [Out of the inbox: a knowledge platform for a pharma logistics provider](https://t10.de/en/blog/knowledge-platform-pharma)
- [Online shops: Shopify and Shopware 5 agency](https://t10.de/en/online-shops)
- [AI product copy and SEO content with RAG](https://t10.de/en/seo)

## Sources

1. [SEVOCAB: application programming interface (API), Definition aus ISO/IEC/IEEE 26514:2022, 3.1.6](https://pascal.computer.org/sev_display/search.action?term=application+programming+interface), IEEE Computer Society und ISO/IEC JTC 1/SC 7 (SEVOCAB), accessed 2026-11-07
2. [Application Programming Interface](https://www.gabler-banklexikon.de/definition/application-programming-interface-99878), Gabler Banklexikon (Springer Gabler), accessed 2026-11-07
3. [Architectural Styles and the Design of Network-based Software Architectures (Dissertation, 2000), Kapitel 5: Representational State Transfer (REST)](https://ics.uci.edu/~fielding/pubs/dissertation/rest_arch_style.htm), Roy T. Fielding, University of California, Irvine, accessed 2026-11-07
4. [IT-Grundschutz-Kompendium, Baustein APP.3.1 Webanwendungen und Webservices (Edition 2023)](https://www.bsi.bund.de/SharedDocs/Downloads/DE/BSI/Grundschutz/IT-GS-Kompendium_Einzel_PDFs_2023/06_APP_Anwendungen/APP_3_1_Webanwendungen_und_Webservices_Edition_2023.pdf?__blob=publicationFile&v=3), Bundesamt für Sicherheit in der Informationstechnik (BSI), accessed 2026-11-07