DecisionVariableRole

class DecisionVariableRole

How a decision variable obtains its value in an Instance.

Roles are derived from the Instance’s current structure and can change after transformation. They are separate from Binary, Integer, or other variable kinds. Query one role with decision_variable_role(), or all roles with decision_variable_roles().

Role	Meaning	Value for candidate evaluation
Used	Referenced by the current objective or active constraints	Supplied by the caller
Fixed	A retained, non-used variable with a recorded fixed value	Restored from that value
Dependent	Neither used nor fixed; represented by an expression in other variables	Computed from that expression
Irrelevant	Neither used, fixed, nor dependent	Supplied by the caller, or filled with a default when omitted

Active constraints include regular and special constraints, including an Indicator’s controlling Binary variable. References only from named functions, removed constraints, output objectives, or dependency right-hand sides do not make a variable used. Being irrelevant to solver input does not mean its value cannot affect reporting.

populate_state() explains reconstruction, defaults, canonicalization, and consistency assertions with executable examples.

Dependent

Defined by decision_variable_dependency

Fixed

Fixed by the instance-owned fixed-value table and not used by solver input

Irrelevant

Not used, fixed, or dependent

Used

Used by the objective or active constraints passed to solvers