Arthur's discrete-spectrum decomposition conjecture

Let $G$ be a connected reductive group over a global function field, let $U\subset G(\mathbf A_K)$ be open compact, and let $S=S(U)$ be the finite set of places where $U$ does not contain a hyperspecial maximal compact subgroup. Let $C$ be the chosen algebraically closed coefficient field, and let ${{\mathbb C} A}_{disc}(G,U,C)$ denote the space of discrete automorphic forms on $G(K)\backslash G(\mathbf A_K)/U$ with values in $C$. Let $\Psi(G,U)$ be the set of equivalence classes of Arthur parameters unramified outside $S$. Arthur's conjecture. There is a direct-sum decomposition

$${{\mathbb C} A}_{disc}(G,U,C)=\bigoplus_{\psi\in\Psi(G,U)}{{\mathbb C} A}_{disc,U,\psi}.$$

For each summand, the source further associates a finite set of irreducible unitary representations. This conjectural decomposition organizes the discrete automorphic spectrum by Arthur parameters; its status is not specified in the source.