BPD Usage Model
A Product-development activity is the root of all work for a product (or release of a product, or project).
A development-stream or maintenance-stream represents a major project branch.
A task-stream represents a minor branch for individual or subproject work.
An integration activity represents merging from a checkpoint in one stream to another stream.
A folder activity groups related activities.
A feature activity represents an enhancement.
A bugfix activity represents work to fix a defect.
A feature or bugfix can be decomposed into subactivities.