In modal logic, we write $A \Box \phi$ for "$A$ knows that $\phi$ is true"
But we can also want to write the statement "$A$ knows whether $\phi$ is true": $(A \Box \phi) \lor (A \Box\neg\phi)$.
Is there a generally accepted way to abbreviate this?
EDIT: in fact it would be helpful for me if there was notation (perhaps the same one), that could signify "knows which", for when the formula is quantified over by some variable (e.g. a natural number): "A knows for which $x$ $\phi(x)$ is true": $\forall x\in X, (A \Box \phi(x)) \lor (A\Box \neg \phi (x))$
In the area of modal logic, I think it is more common to use the notation $K_a \varphi$ to formalize "$a$ knows that $\varphi$". For "knowing whether", I've seen people using $J_i$ ("Knowing Whether," "Knowing That," and The Cardinality of State Spaces), $\Delta_i$ (Contingency and Knowing Whether), and $Kw_i$ (Knowing Whether).
Prof. Wang (webpage) has more to say about the "knowing which" case.