Let $(M^{4},\mu_{0})$ be an oriented $4$–manifold with volume form $\mu_{0}$. A definite triple is a triple $\bm{\underline{\omega}}=(\omega_{1},\omega_{2},\omega_{3})$ of $2$–forms on $M$ such that $\text{Span}(\omega_{1},\omega_{2},\omega_{3})$ is a $3$–dimensional positive definite subspace of $\Lambda^{2}T^{\ast}_{x}M$ at every point $x\in M$.