> ## Documentation Index
> Fetch the complete documentation index at: https://docs.kamu.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# RFC-013: Enum representation in YAML encoding

export const YouTubeList = ({id}) => {
  const src = `https://www.youtube.com/embed/videoseries?list=${id}`;
  return <iframe className="w-full aspect-video rounded-xl" src={src} allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowFullScreen></iframe>;
};

export const YouTube = ({id, width}) => {
  const src = `https://www.youtube.com/embed/${id}`;
  return <iframe className="w-full aspect-video rounded-xl" src={src} allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowFullScreen width={width}></iframe>;
};

export const Schema = ({t, id}) => {
  const anchor = id ? id : t.toLowerCase().replace(/\s+/g, "-");
  const link = `/odf/schemas#${anchor}`;
  return <a class="schema-object" href={link}>{t}</a>;
};

export const Term = ({t, id}) => {
  const anchor = id ? id : t.toLowerCase().replace(/\s+/g, "-");
  const link = `/general/glossary#${anchor}`;
  return <a class="glossary-term" href={link}>{t}</a>;
};

export const Diagram = ({src, alt}) => {
  return <div style={{
    display: "flex",
    "flex-direction": "column",
    "align-items": "center"
  }}>
    <img src={src} alt={alt} style={{
    background: "#dddddd",
    "margin-bottom": 0
  }} />
    <span>{alt}</span>
  </div>;
};

[![Issue](https://img.shields.io/github/issues/detail/state/kamu-data/open-data-fabric/62?label=Issue)](https://github.com/kamu-data/open-data-fabric/issues/70)
[![Spec PR](https://img.shields.io/github/pulls/detail/state/kamu-data/open-data-fabric/63?label=PR)](https://github.com/kamu-data/open-data-fabric/pull/63)

**Start Date**: 2023-12-14

**Authors**:

* [Sergii Mikhtoniuk](mailto:sergii.mikhtoniuk@kamu.dev), [Kamu](https://kamu.dev)

**Compatibility**:

* \[V] Backwards-compatible
* [ ] Forwards-compatible

## Summary

Proposes to use `kind: PascalCaseVariantName` convention to standardize how enum variants are differentiated in YAML / JSON serialization format.

## Motivation

Currently, the spec does not specify how enum variants must be differentiated between when ODF structures are serialized in YAML / JSON form.

This part was left to implementations and Kamu just ended up using `kind: camelCaseVariantName`.

## Reference-level explanation

The proposal is to use internally-tagged representation:

```yaml theme={null}
enumProperty:
  kind: PascalCaseVariantName
  foo: bar
```

The internal tagging provides the most concise representation, while remaining non-ambiguous. The slight drawback is that it gives `kind` property a special function, and we should be mindful of name conflicts.

Using the `PascalCase` for variant names makes names appear identical in YAML / JSON to how they appear in ODF schemas.

While `PascalCase` is the representation that should be used by all implementations when outputting YAML/JSON, in the interest of being more forgiving to human input implementations should also tolerate `camelCase` and `lowercase` names when reading YAML/JSON metadata.

Same rules should apply to string enums. For example a property with schema such as:

```json theme={null}
{
  "type": "string",
  "enumName": "SourceOrdering",
  "enum": [
    "ByEventTime",
    "ByName"
  ]
}
```

When serialized to YAML should output `ByEventTime`, and be able to deserialize from `ByEventTime`, `byEventTime`, and `byeventtime`.

## Compatibility

This change is backwards compatible as all existing `DatasetSnapshot`s that exist in YAML format and use `camelCase` naming will still be accepted under the new scheme.

## Drawbacks

N/A

## Alternatives

* [Supported enum representations in `serde`](https://serde.rs/enum-representations.html) (a de facto Rust's standard serialization library)

## Prior art

N/A

## Unresolved questions

N/A

## Future possibilities

N/A