How Should We Be Handling Required `slots` on Nodes?

[ecwood]

While looking for new categories per #302 and #286, I learned that some node categories have required slots that KG2 (as of KG2.8.3) doesn't have. For example, for retrieval source (which I'm considering as a replacement for information resource):

  retrieval source:
    is_a: information content entity
    description: >-
      Provides information about how a particular InformationResource
      served as a source from which knowledge expressed in an Edge, or
      data used to generate this knowledge, was retrieved.
    slots:
      - resource id
      - resource role
      - upstream resource ids
      - xref
    slot_usage:
      resource id:
        required: true
        description: >-
          The InformationResource that served as a source for the
          knowledge expressed in an Edge, or data used to generate this knowledge.
      resource role:
        required: true
        description: >-
            The role of the InformationResource in the retrieval of the
            knowledge expressed in an Edge, or data used to generate this knowledge.
      upstream resource ids:
        description: >-
          The InformationResources that served as a source for the
          InformationResource that served as a source for the knowledge
          expressed in an Edge, or data used to generate this knowledge.

How should we handle this?

[acevedol]

Retrieval source looks reasonable to me.