Content Reference Model

Predicates are expressions that say something about the world. They evaluate to true or false.
Terms are expressions identifying entities (abstract or concrete) that exist in the world and that agents talk and reason about.
- Concepts expressions that indicate entities with a complex structure that can be defined in terms of slots
- Agent actions special concepts that indicate actions that can be performed by some agents
- Primitives expressions that indicate atomic entities such as strings and integers.
- Aggregates expressions indicating entities that are groups of other entities
- Identifying Referential Expressions expressions that identify the entity (or entities) for which a given predicate is true
- Variables expressions (typically used in queries) that indicate a generic element not known apriori.