Enum Mechanism 

pub enum Mechanism {
    Linear {
        sign: MechanismSign,
        slope: f64,
    },
    Monotonic {
        sign: MechanismSign,
    },
    Threshold {
        sign: MechanismSign,
        threshold: f64,
    },
    Saturating {
        sign: MechanismSign,
        half_max: f64,
    },
    Unknown,
}

v0.45: structural causal mechanism on a directed edge.

A Mechanism captures how a parent finding determines a child’s value, not just that a dependency exists. With mechanisms in place, the kernel can answer counterfactual (Pearl level 3) queries: “given that we observed X under parent=p, what would X have been under parent=p’?” via twin-network construction.

Doctrine: mechanisms are deliberately coarse. Science rarely warrants precise functional forms; what we need is enough algebraic structure to propagate counterfactual perturbations sign-and-magnitude. Five shapes cover the empirical distribution of biology / clinical claims:

• Linear { sign, slope }: dY = slope * dX (with sign packing the direction; slope is a unitless effect-size on the [0,1] confidence scale).
• Monotonic { sign }: dY agrees with sign(dX) but magnitude is ungraded (used when direction is known but effect-size isn’t).
• Threshold { sign, threshold }: parent must cross threshold for any child response (binary above/below).
• Saturating { sign, half_max }: hyperbolic / Hill-style; large dX above half_max produces vanishing dY.
• Unknown: explicitly annotated as causally connected but mechanism unspecified. Twin-network treats this as opaque (the counterfactual is reported as MechanismUnspecified).

Variants

Linear

Fields

sign: MechanismSign

slope: f64

Effect-size on [0, 1] confidence scale.

Monotonic

Fields

sign: MechanismSign

Threshold

Fields

sign: MechanismSign

threshold: f64

Saturating

Fields

sign: MechanismSign

half_max: f64

Unknown

Implementations

impl Mechanism

pub fn apply(&self, delta_x: f64) -> Option<f64>

Apply this mechanism to a parent perturbation delta_x, returning the implied child perturbation delta_y on the confidence scale. Returns None for Unknown.

Trait Implementations

impl Clone for Mechanism

fn clone(&self) -> Mechanism

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Mechanism

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl<'de> Deserialize<'de> for Mechanism

fn deserialize<__D>(__deserializer: __D) -> Result<Self, __D::Error>

where __D: Deserializer<'de>,

Deserialize this value from the given Serde deserializer.

impl PartialEq for Mechanism

fn eq(&self, other: &Mechanism) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Serialize for Mechanism

fn serialize<__S>(&self, __serializer: __S) -> Result<__S::Ok, __S::Error>

where __S: Serializer,

Serialize this value into the given Serde serializer.

impl Copy for Mechanism

impl StructuralPartialEq for Mechanism