Feature

A feature is a typed component of subroutine state. Edge conditions observe its value; edge effects constrain its change. Every feature starts uninitialized and receives values through Feature-node visits.

Countdown example

The Countdown subroutine owns one feature:

Feature property	Countdown
ID	counter
Kind	Integer (non-negative int)
Initial value	None at graph entry; the initialize_counter visit proposes the invocation's Count.value
Initialization effect	counter? on initialize_counter → check_counter permits the first integer value
Declaration	◆ features/counter/__init__.py

Feature kinds

Kind	Python value	Conditions can observe
Boolean	bool	true or false
Integer	non-negative int	zero or greater than zero
Float	finite, non-negative float	zero or greater than zero
Enum	str	one declared value

Authored files

Features have no authored module or initializer callback. Initialization and updates belong to authored Feature visits, stored at ● nodes/<node>/visit/<edge-id>/impl.py.

Initialization

Every subroutine invocation starts with all feature values set to None. A Feature visit proposes the first domain value through state.replace(FEATURE, value). Evaluating a condition on an uninitialized feature raises ValueError. Increase and decrease effects also require an initialized source value, whereas assignment and unconstrained effects can initialize a feature. An unchanged effect preserves None. Once initialized, a feature cannot be reset to None.

Conditions read the state before the source visit. An initialization node must therefore precede any node whose outgoing conditions read the initialized feature; a condition on the initialization node's own outgoing edge would still read None.

Conditions and effects

Conditions and effects do not add files to the feature directory. They update each affected ◆ edges/<edge-id>/__init__.py declaration, which imports this feature's entry from FEATURE_IDS and builds the corresponding typed observation.

Only an edge originating at a Feature node may carry explicit effects. Edge defines the observations; Visit describes the candidate values against which the runtime evaluates them.

Files

Each feature has a generated declaration and no authored file. Its subroutine also has one generated registry for all feature declarations.

General feature structure

features/
├── ◆ __init__.py
└── <feature>/
    └── ◆ __init__.py

File	Role
◆ features/<feature>/__init__.py	Declares the feature ID, label, description, kind, and allowed enum values.
◆ features/__init__.py	Imports every FEATURE in the subroutine and exports them as the FEATURES tuple.

Generated files

See the generated declaration reference for the Python declarations and registries maintained by generation.