Draft release notes for 3.2.0 and 3.1.2

draft-release-notes.md

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+# [DRAFT]: Release Notes
+
+What's coming up? Look at `src/oas.md` on the relevant development branch for full details.
+
+## 3.2 Updates
+
+### Support additional HTTP methods
+
+- Support the new `query` method alongside the existing `get`/`post`/`put`/`delete`/`options`/`head`/`patch`/`trace`.
+- Under an `additionalOperations` entry in a Path, use any other methods not listed as keys using the correct capitalization. e.g. do NOT add HEAD under this, use the existing sibling `head`.
+
+### Nested, multipurpose tags
+
+- New `summary` field to allow short descriptions, used when displaying lists of tags. If you use the `x-displayName` extension, you can now use `summary` instead.
+- `parent` field to point to the tag that this tag is nested under. If you use `x-tagGroups`, adjust to use a tags hierarchy.
+- `kind` to allow multiple categories of tag. The `kind` field is free-form text, however there are some expected/conventional values such as `nav` (in line with the most common current usage as grouping for documentation output).
+- A [registry](https://spec.openapis.org/registry/tag-kind/index.html) to establish conventions for values used in `kind`.
+
+### Updated security schemes
+
+- Support for OAuth2 Device Authorization flow with additional `deviceAuthorization` field in the `flows` object and for the individual flow, a new field `deviceAuthorizationUrl` alongside `tokenUrl`.
+- Additional security scheme field: `oauth2MetadataUrl` URL for auth server metadata.
+- Additional `deprecated` field for security schemes (indicating that the scheme may still be supported, but that it should not be used).
+- Ability to reference a security scheme by URI rather than needing it declared in components.
+
+### Servers
+
+- Clarify that server URLs should not include fragment or query.
+- Support new `name` field alongside `description`, `url` and `variables`.
+- Formal path templating support for variable substitution in server urls.
+
+### Better polymorphic support
+
+- The discriminator `propertyName` can now be an optional field.
+- Additional `defaultMapping` field to indicate which schema to use if the `propertyName` is not set, or if the value is unrecognized.
+- No change from previous versions: use `discriminator` to hint which entry in `anyOf` or `oneOf` is expected.
+- No change from previous versions: use `mapping` to link the discriminator property value to the Schema name if they aren't an exact match.
+- Implementations now SHOULD (rather than MAY) support templates/generics using `$dynamicRef`.
+
+### Reference resolution
+
+Additional top-level `$self` to be used as a base URI for resolving references in the OpenAPI description. If not present, the existing/earlier behaviour of using the retrieval URL as a base applies.
+
+### Path templating
+
+**ABNF** (Augmented Backus–Naur Form) formalised for path templating, server variables, and runtime expressions in the Links object.
+
+### Improvements for APIs using XML as a content format
+
+- New `nodeType` field allows mapping schemas to common XML node types: `element`, `attribute`, `text`, `cdata`, or `none`.
+- `attribute: true` deprecated in favor of `nodeType: attribute`.
+- `wrapped: true` deprecated in favor of `nodeType: element` (as `nodeType` defaults to `none` for arrays to preserve compatibility).
+- The `xml` keyword can be used in any Schema Object.
+- XML namespaces can be IRIs (rather than URIs).
+- Explanation and example on how to handle `null` in XML.
+- Clarify that the root schema of an XML object should use the component name.
+
+### Support for sequential media types
+
+- Support for sequential media types such as `text/event-stream` for server-sent events (SSE) and `application/jsonl`, `application/json-seq` and others for sequential data.
+- Responses can be a repeating data structure, and are treated as if they are an array of schema objects.
+- Use `itemSchema` in a mediatype entry to describe each item.
+- Related: a new media types registry is published to give more context for each of the media types.
+- Also a "Complete vs Streaming Content" section for guidance on streaming binary payloads.
+
+### Parameter and header changes
+
+- Additional parameter location `querystring`, to allow parsing the entire query string as a single field similar to the way a request body is handled, using the `content` field. Useful for complex or unconventional query data. Mutually exclusive with the `query` field.
+- Parameters can therefore be `in` the `querystring` as an alternative to the existing `header`, `cookie`, `query` and `path` values.
+- `allowReserved` field is now permitted on headers and on parameters with any value of `in`.
+- Remove incorrect mention of Reference Object in the header `schema` field. The JSONSchema ref would be the correct thing to use in this context.
+
+### Flexible response metadata fields
+
+- `description` field for responses are now optional (they used to be required but they could be empty).
+- Additional `summary` field for responses, useful when displaying responses in a list context.
+
+### Minor edits that are worth a mention
+
+- Streamlined to YAML examples (unless something specific to another format) to try to make it easier to follow.
+
+### In-place updates to existing specifications and standards that we reference
+
+- Update to <https://www.ietf.org/archive/id/draft-bhutton-json-schema-01.html> of JSON Schema Specification.
+- Update to <https://www.ietf.org/archive/id/draft-bhutton-json-schema-validation-01.html> of JSON Schema Validation Specification.
+- Use [RFC8529](https://tools.ietf.org/html/rfc8259) for JSON.
+- Use [RFC9110](https://tools.ietf.org/html/rfc9110) for HTTP.
+
+### Editorial changes
+
+- Extensive additions around media types, encoding, sequential media types, SSE examples, working with binary data.
+- Clarification that Example Objects can be used in Header Objects.
+- Better explanation and examples for using Encoding.
+- Clarify that Request Body Objects need to specify at least one media type to be meaningful.
+- How to more clearly indicate that responses will not have a body.
+
+## 3.1 Updates
+
+Version 3.1.2 has no material changes but does contain editorial fixes.
+
+- Clarification that Example Objects can be used in Header Objects.
+- Better explanation and examples for using Encoding.
+- Clarify that Request Body Objects need to specify at least one media type to be meaningful
+- How to more clearly indicate that no response will have a body
+- How to handle `null` in XML as an advisory note; since the functionality cannot be changed it is implementation-defined for 3.1 tooling.
+- Clarify that the root schema of an XML object should use the component name.
+
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