Metamodel.id/NamespacedEntity.id vs. Node id

[enikao]

In the concept field of a node, do we refer to the Concept's node id or id property?

When referring to Metamodels, we have even more options:

• Metamodel's node id
• Metamodel's id property
• Metamodels's name property

How stable does the id (whichever we'll use) need to be, especially between different repositories?

[dslmeinte]

You could ask the same question about regular models (=M1s). Are we catering for the use case that a language is persisted in one repository, but models conforming to it in an entirely different one without that having a local copy?

[enikao]

I think that's different: A repository must govern its node ids, in order to guarantee uniqueness. That's why we proposed in #25 that we need to ask the repo for valid ids before we create any new node. If we moved these nodes to a different repo, the new repo might need to assign new ids because the used ones are already taken.

[enikao]

We had a related discussion in #46

[ftomassetti]

I find confusing to have two Metamodel IDs: one represent the id of the Metamodel and one the id of the Metamodel declaration. I would explore possibilities to keep just one of them and if that is not possible than I think we would need to rename the property to something like language-id

[enikao]

Decision on 2023-03-03:

References from M1 to M2 are called meta-links, and conceptually always form triplets; details in #89.

[enikao]

Decision on 2023-03-03:

References within a metamodel use the regular node ids.
Rationale: A metamodel in itself is "just a model", thus references are "just regular references". They do not cross metalevel boundaries.

Example:

Metamodel MyLanguage          [key: "My-language", nodeid: "dt21"]

  Concept Place               [key: "aaa", nodeid: "ac34"]
    property street: string   [key: "aab", nodeid: "sd3"]

  Concept Person              [key: "bbb", nodeid: "kj54"]
    reference address: Place  [key: "bbc", nodeid: "xvc3"]

The reference from Person.address.type to Place is serialized as ac34.