This total Hamiltonian is traditionally called the Dirac Hamiltonian. Constraints arise naturally from parameter invariant actions of the form I = ∫ ∫ d τ τ L ( τ τ ) = ∫ ∫ d τ τ ′ d τ τ d τ τ ′ L ( τ τ ) = ∫ ∫ d τ τ ′ L ( τ τ ′ ) .