diff --git a/internal/registry/expr.go b/internal/registry/expr.go
index 71db96d..7d4d506 100644
--- a/internal/registry/expr.go
+++ b/internal/registry/expr.go
@@ -18,9 +18,9 @@ type baseExpr struct {
 	data any
 }
 
-func (r baseExpr) Repr() string { return r.id }
+func (e baseExpr) Repr() string { return e.id }
 
-func (r baseExpr) Data() any { return r.data }
+func (e baseExpr) Data() any { return e.data }
 
 // NewExpr creates an Expr with the given representation name and data.
 func NewExpr(id string, data any) Expr { return baseExpr{id, data} }
diff --git a/internal/registry/process.go b/internal/registry/process.go
index 2a83685..b39227c 100644
--- a/internal/registry/process.go
+++ b/internal/registry/process.go
@@ -4,28 +4,32 @@ import (
 	"git.maximhutz.com/max/lambda/pkg/engine"
 )
 
+// A Process is a type-erased reduction process that operates on Expr values.
 type Process interface {
 	engine.Process[Expr]
 
+	// InType returns the name of the representation this process operates on.
 	InType() string
 }
 
+// A registeredProcess adapts a typed engine.Process[T] into the type-erased
+// Process interface. It wraps the result of Get into an Expr.
 type registeredProcess[T any] struct {
 	process engine.Process[T]
 	inType  string
 }
 
-func (e registeredProcess[T]) InType() string { return e.inType }
+func (p registeredProcess[T]) InType() string { return p.inType }
 
-func (b registeredProcess[T]) Get() (Expr, error) {
-	s, err := b.process.Get()
+func (p registeredProcess[T]) Get() (Expr, error) {
+	s, err := p.process.Get()
 	if err != nil {
 		return nil, err
 	}
 
-	return NewExpr(b.inType, s), nil
+	return NewExpr(p.inType, s), nil
 }
 
-func (b registeredProcess[T]) Step(i int) bool {
-	return b.process.Step(i)
+func (p registeredProcess[T]) Step(i int) bool {
+	return p.process.Step(i)
 }