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Since a system $S$ may be inconsistent with the set $T(S)$ of all its typical atoms, it may have no most typical model. But $S$ must have a typical model containing a subset of $T(S)$ consistent with $S$. It would be helpful to characterize a subset of typical atoms of any system $S$ that is necessarily consistent with $S$ regardless of beliefs assigned to other atoms of $S$. If for a given system this subset is non-empty then queries about atoms of the subset can be answered obliviously in any order.

\[def-neighb\] (i) Considering any model as a set of literals, call two models\
$m', m''$ $\mathbf{a}$-*neighbors* if they differ only in the value of an atom $\mathbf{a} \in Base(S)$ such that $\mathbf{a} \in m'$, $\neg \mathbf{a} \in m''$, and $m' - \{\mathbf{a}\} = m'' - \{\neg \mathbf{a}\}$. Let $MN(S \cup \{\mathbf{a}\})$, $MN(S \cup \{\neg \mathbf{a}\})$ denote sets of all $\mathbf{a}$-neighboring models of $S$ such that every model of $MN(S \cup \{\mathbf{a}\})$ contains $\mathbf{a}$, every one of $MN(S \cup \{\neg \mathbf{a}\})$ contains $\neg \mathbf{a}$, and to every model of $MN(S \cup \{\mathbf{a}\})$ corresponds exactly one $\mathbf{a}$-neighbor in $MN(S \cup \{\neg \mathbf{a}\})$, and vice versa.

\(ii) If for a typical 