BPMN21 — Define "Pool"

The term "pool" is used extensively in the specification yet the definition seems inconsistent and not tied to the meta model. Sometimes a pool seems to be the role of a participant in a process context. In other cases it seems to be the essential container of a process. It seems to be a graphical element but shows up on ends of associations and in definitions of the semantics. The term "pool" does not seem to have any semantic relevance to process.
Examples:
• While a normal Process exists within a Pool, a Choreography exists between Pools (or Participants).
• A Pool is the graphical representation of a Participant in a Collaboration (see page 235). It is also acts as a "swimlane" and a graphical container for partitioning a set of Activities from other Pools, usually in the context of B2B situations.
• Nor can Sequence Flow cross a Pool boundary.
• For message exchanges between pools, Conversations are used to group several Message Flow
• A Participant is a specific business entity (e.g., a company) or a more general business role (e.g., a buyer, seller, or manufacturer) responsible for the execution of the Process enclosed in a Pool.

The semantics behind of pool should be clarified and the spec should not use graphical elements to define semantics.