Performance
	Pre-define ObjectType accessor methods on constellation, rather than using method_missing

Role objects:
        TEST: Access through class-level accessors

Reindexing on identifier change
	De-index on change, arrange for re-index on completion
	Re-index all objects this identifies (keep track of roles-as-identifier)
	Save "key" value
	Nested block to accumulate changed identifiers and re-index at end?

Switch to rbtree from Hash
        For InstanceIndex
	For RoleValues
	Index into RoleValues by key residual, not full key (worth doing?)

Testing
	Complete pending tests
	Add heckle coverage

Constraints
	Ensure role methods arguments are flexible for plugins
	Make mandatory work (propagate retraction? or just optionally?)

Functionality
	Finish Constellation.assert
	Replace inspect by verbalise
	Query API and execution