Edge

An edge connects a source node or enter port to an executable node, exit port, or failure port. Its conditions constrain the source feature state; its effects constrain a Feature node's candidate state. An edge entering an executable node selects that arrival path's visit.

Countdown example

The Countdown graph contains these six edges:

Edge ID	Connection	Condition	Effect
enter__initialize_counter	enter → initialize_counter	—	—
initialize_counter__check_counter	initialize_counter → check_counter	—	counter? permits its first value
check_counter__decrement	check_counter → decrement	counter > 0	—
decrement__update_counter	decrement → update_counter	—	—
update_counter__check_counter	update_counter → check_counter	—	counter decreases
check_counter__exit	check_counter → exit	counter = 0	—

Conditions

A condition enables an edge only when the current feature state satisfies every listed observation.

Here $b$ denotes a Boolean feature, $z$ a numerical feature, $c$ an enum feature, and $d$ one of that enum's declared values.

Feature kind	Notation	Required current value
Boolean	$b$	true
Boolean	$\mathrm{\neg }b$	false
Integer or float	$z=0$	zero
Integer or float	$z>0$	greater than zero
Enum	$c=d$	equal to $d$

The generated declaration for an edge with conditions imports the scope's FEATURE_IDS and stores typed condition objects in conditions. Conditions observe the feature state from before the source node runs; effects inspect a Feature node's proposed state.

Effects

Explicit effects describe how feature state may change across a Feature node. They are allowed only when that node is the edge's source.

Feature kind	Notation	Required next value
Boolean	$b:=\mathrm{\top }$	true
Boolean	$b:=\mathrm{\perp }$	false
Boolean	$b=$	unchanged
Boolean	$b?$	unconstrained
Integer or float	$z\uparrow$	strictly greater than the current value
Integer or float	$z\downarrow$	strictly smaller than the current value
Integer or float	$z=$	unchanged
Integer or float	$z?$	unconstrained
Enum	$c:=d$	equal to $d$
Enum	$c?$	unconstrained

The runtime evaluates every outgoing edge against the source and candidate states. It commits the candidate state only when exactly one edge satisfies both its conditions and effects; zero or multiple compatible edges cause a routing error. An arrow denotes a strict comparison, not a change of exactly one. A question mark permits any initialized value in the feature's domain. A feature omitted from the effect list must remain unchanged, including when its value is None.

Editing an effect regenerates the edge's ◆ edges/<edge>/__init__.py declaration.

Parallel edges

Edge identity is independent of endpoint identity; multiple edges may therefore connect the same pair of nodes. Each edge retains its own declaration, conditions, effects, and visit.

The first automatically derived ID is <source>__<target>. A parallel edge receives a distinct ID such as <source>__<target>__2. Because the edge ID names both its generated declaration directory and the visit directory below the target, parallel edges cannot collide. A custom edge ID uses lowercase snake_case and remains independent of its endpoints.

Authored files

Edges have no authored files. When an edge targets an executable node, it selects a visit whose generated and authored files are stored below that target node. Edges into exit or failure create no visit files.

Files

Each edge has its own generated package beside the generated edge registry:

General edge structure

edges/
├── ◆ __init__.py
└── <edge>/
    └── ◆ __init__.py

File	Role
◆ edges/<edge>/__init__.py	Declares one edge's ID, name, endpoints, conditions, effects, and optional visit.
◆ edges/__init__.py	Imports every directly owned EDGE declaration and exports the ordered EDGES tuple.

Generated files

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