OpenAPI Specification

The OpenAPI (OAI) Specification defines a standard, programming language-agnostic interface description for RESTful APIs. OAI is a simple text file that can be edited with any text editor. The text files describe an OAI document and are represented in either YAML (YAML Ain't Markup Language) or JSON (Javascript Object Notation) formats. Such OAI documents can include interactive documentation, code generation for documentation, clients and servers and automation of test cases.

Purpose of OpenAPI

OAI is a community-driven open specification within the OpenAPI Initiative, a Linux Foundation Collaborative Project. OAI's stated purpose, according to the OpenAPI Initiative, is to focus on creating, evolving and promoting a vendor-neutral description format. In doing so, its proponents -- notably SmartBear Software, which donated its Swagger Specification to the OpenAPI Initiative -- say it will accelerate the proliferation of APIs and help connect corporate data sources, third party data services and other applications.

Benefits of OpenAPI

OAI does not require rewriting existing APIs. It does not require binding any software to a service. OAI does not mandate a specific development process such as design-first or code-first. It does facilitate either technique by establishing clear interactions with a REST API.

OAI does have limitations as all services or every style of REST APIs can be described by OAI.

History of OpenAPI

The OpenAPI Initiative was created in 2015 by a consortium of 10 technology-centric companies and remains an open governance structure under the Linux Foundation. The consortium was led by SmartBear and also includes 3Scale, Apigee, Capital One, Google, IBM, Intuit, Microsoft, PayPal and Restlet.

In forming the Open API Initiative, SmartBear donated its Swagger specification to the Linux Foundation, and OAI reflects its lineage as the follow-on the specification known as Swagger 2.0. In 2010, Wordnik created the Swagger specification under an open source license. In March 2015, SmartBear acquired Wordnik’s interests in the Swagger projects from its parent company, Reverb Technologies. SmartBear in 2015 donated the Swagger Specification as part of the formation of the OpenAPI Initiative. Following the announcement of the OAI, the Swagger specification was renamed OAI.

This was last updated in August 2019

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