A square

will be called $\mathbb E$-$K$-deductive if the following data exist:

• an exact $\mathbb E$-modification $\lambda$ from $(S,T)$ to
• an exact $\mathbb E$-modification $\mu$ from $(U,V)$ to
• a morphism $k : a’\to b’$ of $K$ such that $k * \lambda=\mu$.