119 lines (66 sloc) 9.31 KB

Development Guidelines

This document intends to establish guidelines which build a transparent, open mechanism for deciding how to evolve the OpenAPI Specification. The OpenAPI Technical Steering Committee (TSC) will initially follow these processes when merging changes from external contributors or from the TSC itself. This guideline document will be adjusted as practicality dictates.

OAI Specification Driving factors

The OpenAPI Specification should be use-case driven. We can specify support for hypothetical use cases as we see fit, but specifications should be backed by realistic scenarios.

Specification Change Criteria

The specification will evolve over time. Changes may be made when any of the following criteria are met:

  • Clarity. The current "way" something is done doesn't make sense, is complicated, or not clear.

  • Consistency. A portion of the specification is not consistent with the rest, or with the industry standard terminology.

  • Necessary functionality. We are missing functionality because of a certain design of the specification.

  • Forward-looking designs. As usage of APIs evolves to new protocols, formats, and patterns, we should always consider what the next important functionality should be.

  • Impact. A change will provide impact on a large number of use cases. We should not be forced to accommodate every use case. We should strive to make the common and important use cases both well supported and common in the definition of the OAI Spec. We cannot be edge-case driven.

Specification Change Process

For each change in the specification we should always consider the following:

  • Migration. Is this a construct that has a path from the existing 2.0 specification? If so, how complicated is it to migrate to the proposed change?

  • Tooling. Strive to support code generation, software interfaces, spec generation techniques, as well as other utilities. Some features may be impossible to support in different frameworks/languages. These should be documented and considered during the change approval process.

  • Visualization. Can the specification change be graphically visualized somehow in a UI or other interface?

Spec changes should be approved by a majority of the committers. Approval can be given by commenting on the issue itself, for example, "Approved by @webron" however at least one formal GitHub-based flow approval must be given. After voting criteria is met, any committer can merge the PR. No change should be approved until there is documentation for it, supplied in an accompanying PR.

Tracking Process

  • GitHub is the medium of record for all spec designs, use cases, and so on.

  • As with 2.0, the human readable document is the source of truth. If using a JSON Schema again to document the spec, it is secondary to the human documentation. The documentation should live in a *.md file, in parallel to the 2.0 document (versions/ for example).

  • At any given time, there would be at most 4 work branches. The branches would exist if work has started on them. Assuming a current version of 3.0.0:

    • master - Current stable version. No PRs would be accepted directly to modify the specification. PRs against supporting files can be accepted.

    • v3.0.1-dev - The next PATCH version of the specification. This would include non-breaking changes such as typo fixes, document fixes, wording clarifications.

    • v3.1.0 - The next MINOR version.

    • v4.0.0 - The next MAJOR version.

  • The master branch shall remain the current, released OpenAPI Specification. We will describe and link the work branch(es) on the default on master.

  • Examples of how something is described currently vs. the proposed solution should accompany any change proposal.

  • New features should be done in feature branches/forks which, upon approval, are merged into the proper work branch.

  • Use labels for the workflow of specification changes. Examples of labels are proposed, housekeeping, migration-review, tooling-, needs documentation, review (candidate for upcoming TSC mtg), rejected, and needs approval. These labels must be assigned by project committers. Style is lowercase with dashes in place of spaces.

  • An issue will be opened for each feature change. Embedded in the issue, or ideally linked in a file via pull-request (PR), a document about use cases should be supplied with the change.

  • A PR will be used to describe the proposed solution and linked to the original issue.

  • Not all committers will contribute to every single proposed change. There may be many open proposals at once, and multiple efforts may happen in parallel.

  • When the work branch is ready and approved, the branch will be merged to master.

Release Process

A release requires a vote on the release notes by TSC members within the voting period. Major or minor release voting periods will be announced by the Liaison in the Slack channel and noted on the calendar at least 6 days in advance. During this time, TSC members who have not yet voted must note their approval on the GitHub pull request for the release notes. Patch releases happen at the first TSC meeting of a calendar month. The Liaison is responsible for coordinating the actual merge to Master with marketing support, if any.

  • Patch-level releases require majority approval by TSC members. (Max voting period 3 days)

  • Minor: requires approval by 66% of TSC members. (Max voting period 7 days)

  • Major: requires approval by 66% of TSC members. (Max voting period 14 days)

Draft Features

Where suitable, features will be introduced as draft but OAI approved extensions. By introducing new features this way we enable new features to be designed, documented and then implemented by tools that are interested in the feature, without putting the burden of implementation on all tooling. If the feature is successfully implemented and there is demonstrable value added by the feature, it will become a candidate for inclusion in a future release of the specification, at which point all tools will be expected to support the feature.

Draft feature extensions are identified by the x-oas-draft- prefix and can only be used where existing extensions are permitted. This ensures no existing tooling will affected by the introduction of the draft feature. If the feature is deemed appropriate for inclusion in the OAS, the x-oas-draft- prefix will be removed. Tooling that supports draft features should plan for the future removal of the prefix. When tooling adds support for a later version of OAS that includes the final implementation of the feature, it MUST not support the use of the draft prefix for that feature. Draft features will only be promoted into minor or major releases of the specification and therefore will be transparent to OpenAPI description writers and tooling providers who choose not to use the feature while in its draft state.

Draft features will be documented as GitHub issues and labeled with the draft-feature label and will be initially labelled as draft:proposal. When the proposal is considered sufficiently stable for pilot implementation, it will be labeled draft:pilot. If during the development of a draft feature, it is determined that the feature needs to change in a way that may break existing draft implementations, the extension name itself may be versioned with a version suffix. e.g. -v2 When a draft feature becomes part of a future update to the specification any version suffix will be removed. Draft features that are deemed not appropriate for inclusion MUST be marked with the draft:abandoned label. Draft-features that are considered suitably specified and have had successful pilot implementations will be marked with the draft:graduated label.

Not all future new features will be introduced in this way. Some new features impact the specification in ways that cannot be encapsulated in an extension. However, where a new feature can be introduced in this way, it should be.


The process should be as transparent as possible. Sometimes there will be discussions that use customer names, sensitive use cases, and so on. These must be anonymized, discussed in a private repository, or conducted offline. General discussions should happen on the GitHub issues for this project.


While governance of the specification is the role of the TSC, the evolution of the specification happens through the participation of members of the developer community at large. Any person willing to contribute to the effort is welcome, and contributions may include filing or participating in issues, creating pull requests, or helping others with such activities.

Community Roles

While these developer community roles are informal, there are many ways to get involved with the OpenAPI community, such as:

  • Contributor: Includes but is not limited to any contributor to the specification via an accepted pull request or who participates in issues or TSC calls.

  • Implementer: any person involved in the creation or maintenance of tooling that leverages the current OpenAPI Specification

  • Ambassador: represents the OpenAPI Specification to the developer community. This could be through talks at conferences or meetups, blog posts, or answering questions in places like Twitter, Stack Overflow, or the GitHub repo.

  • Supporter: uses the specification and appreciates its value.