Where does hierarchical structure occur?

Vector representations are widely used for representing unstructured objects, e.g., bag-of-words style vector representations as used in information retrieval, but the emphasis in VSA's is on representation and processing of hierarchical compositional structure.

But, where does hierarchical compositional structure occur?

• In language constructs that refer to other entity's states of mind (cf Robin Dunbar's “Gossip” theory of the evolution of language), e.g., "Pat thinks Tom loves Robin"
  
• In planning (cf Mark Steedman's work on planning)