Refer to EnumLiteral by key?

[enikao]

In the serialization format, for properties of an enum type, we refer to the key of the literal.

Options

Option A: Refer to the literal's key

Pro:

• Stable across different repositories
• Stable against renamed literals

Con:

• Cannot interpret the property without the metamodel

Option B: Refer to the literal's id

Con:

• Cannot exchange M1 data between repositories, as they might use different ids for the M2 literal node.
• Cannot interpret the property without the metamodel

Option C: Refer to the literal's name

Pro:

• Property value easily understood without metamodel

Con:

• If the user changed the name of the literal, we cannot read older M1 instances any more.

Rationale

• The instance is on M1, the literal on M2. Every time we cross a meta-level, we use keys.
• Most stable

Example

Assume the following metamodel:

language Bank [key: AAA]
version: 1

concept Payment  [key: aaa]
  property amount: int  [key: bbb]
  property currency: Currency  [key: ccc]

enum Currency  [key: ddd]
  literal EUR  [key: eee]
  literal USD  [key: fff]

And the following instance:

Currency:
  amount: 42
  currency: EUR

The instance would be serialized as:

{
  "nodes": [
    {
      "id": "111",
      "concept": {
        "language": "AAA",
        "version": "1",
        "key": "aaa"
      },
      "properties": [
        {
          "property": {
            "language": "AAA",
            "version": "1",
            "key": "bbb"
          },
          "value": "42"
        },
        {
          "property": {
            "language": "AAA",
            "version": "1",
            "key": "ccc"
          },
          "value": "eee"
        }
      ],
      "children": [],
      "references": [],
      "parent": null
    }
  ]
}

[enikao]

Decision in meeting on 2023-05-05: Option A: Refer to the literal's key

We accept that instance models cannot be understood without the metamodel, as we're a metamodel-based system.