Concept is a central entity, some kind of a hub, which binds and defines the roles of all other entities. Every entity present in the model, should be defined as a Concept.

Requirements:

• must have name
• must belong to Domain
• must be declared in Vocabulary
• must be classified by Concept Class
• must have a code from source vocabulary
• must have a defined validity period

Options:

• might be Classification, Standard or non-standard Source Concept(default)
• might be invalidated. “D” - deleted, “U” - updated, NULL - concept is valid(default)

Each Concept has its own unique ID.