Parts and the declaration model

Draft

This page is scaffolded. The outline below marks what it should cover; the Parts reference already renders every stock part from its docstring.

A Part is an atomic unit of behavior on a craft, and a craft is a tree of them. Parts declare their interface at class scope using five sentinels, and the framework walks those declarations at compile time to build the symbolic graph.

To cover

• The five declaration sentinels — what each is and when to reach for it:
  • Parameter(default, manifold=…) — frozen at construction; baked into the graph (promotable for Fit).
  • State(init, manifold="R1"|"R3"|SO3Manifold(...)) — mutable per-tick state with manifold-correct boxplus.
  • Input(default) — per-tick user value.
  • Output(shape) — per-tick observable (a sensor reading).
  • Noise(shape, kind="white"|"rw", sigma) — white noise or an RW-bias state that synthesizes its own slot + driver.
• The craft tree — composite parts, mounting transforms, frames (PartFrame, ParentFrame, CraftFrame).
• update() and PartUpdate — how a part contributes a Wrench and/or state derivatives each tick.
• How declarations feed the transforms — a Noise channel becomes a Q/R contribution in the EKF; an Output becomes a measurement; a manifold Parameter becomes a fit variable.

Source material

• Reference: Parts
• Code: manta/parts/base.py, manta/parts/_declarations.py