TOFType.ConceptType currently carries two vocabularies: the legacy ELM values (Person, Organisation, Event, Role, Location, Composition, Aggregation, Rule, Book) and ArchiMate element types (Business_Object, Business_Actor, Business_Role, Business_Event, Application_Component, Application_DataObject, Technology_Node, ...). ArchiMate values pass straight through, and the value drives the ArchiMate element shape plus the conceptual icon.

Request: add C4 as a third vocabulary, aimed at application design rather than enterprise architecture - Person, Software System, Container, Component, Code Element - so a model can be annotated for a C4 context/container/component view.

Notes on scope:

• The MCP side is nearly free: concept_type already accepts and reports free-form values, so C4 names pass through with only a description change.
• The real work is in the drawing layer: shapes/icons per C4 element, and the level-based view selection (context / container / component / code) which has no ArchiMate equivalent.
• Relation derivation currently follows the ConceptType or the source/target pair (see the ArchiMate work); C4 relationships are simpler (uses / delivers / reads-writes) and would need their own mapping.
• Worth deciding early whether C4 lives beside ArchiMate in the same ConceptType string or becomes its own annotation axis, since a model may legitimately carry both an ArchiMate and a C4 classification.

Raised while extending the MCP metadata surface (temporal flags, metalevel, classification roles): the higher meta levels behave like UML stereotyping, and C4 is the obvious third stereotype family to support.