We consider a sequence $\mathbf{T} = (\mathcal{T}_n : n \in \mathbb{N}^+)$ of trees $\mathcal{T}_n$ where, for some $\Delta \in \mathbb{N}^+$ every $\mathcal{T}_n$ has height at most $\Delta$ and as $n \to \infty$ the minimal number of children of a nonleaf tends to infinity. We can view every tree as a (first-order) $\tau$-structure where $\tau$ is a signature with one binary relation symbol. For a fixed (arbitrary) finite and relational signature $\sigma \supseteq \tau$ we consider the set $\mathbf{W}_n$ of expansions of $\mathcal{T}_n$ to $\sigma$ and a probability distribution $\mathbb{P}_n$ on $\mathbf{W}_n$ which is determined by a (parametrized/lifted) Probabilistic Graphical Model (PGM) $\mathbb{G}$ which can use the information given by $\mathcal{T}_n$. The kind of PGM that we consider uses formulas of a many-valued logic that we call $PLA^*$ with truth values in the unit interval $[0, 1]$. We also use $PLA^*$ to express queries, or events, on $\mathbf{W}_n$. With this setup we prove that, under some assumptions on $\mathbf{T}$, $\mathbb{G}$, and a (possibly quite complex) formula $\varphi(x_1, \ldots, x_k)$ of $PLA^*$, as $n \to \infty$, if $a_1, \ldots, a_k$ are vertices of the tree $\mathcal{T}_n$ then the value of $\varphi(a_1, \ldots, a_k)$ will, with high probability, be almost the same as the value of $\psi(a_1, \ldots, a_k)$, where $\psi(x_1, \ldots, x_k)$ is a ``simple'' formula the value of which can always be computed quickly (without reference to $n$), and $\psi$ itself can be found by using only the information that defines $\mathbf{T}$, $\mathbb{G}$ and $\varphi$. A corollary of this, subject to the same conditions, is a probabilistic convergence law for $PLA^*$-formulas.
翻译:我们考虑一个树序列 $\mathbf{T} = (\mathcal{T}_n : n \in \mathbb{N}^+)$,其中对于某个 $\Delta \in \mathbb{N}^+$,每个 $\mathcal{T}_n$ 的高度至多为 $\Delta$,并且当 $n \to \infty$ 时,非叶节点的最小子节点数趋于无穷。我们可以将每棵树视为一个(一阶)$\tau$-结构,其中 $\tau$ 是包含一个二元关系符号的签名。对于一个固定的(任意的)有限关系签名 $\sigma \supseteq \tau$,我们考虑 $\mathcal{T}_n$ 到 $\sigma$ 的展开集合 $\mathbf{W}_n$,以及 $\mathbf{W}_n$ 上的一个概率分布 $\mathbb{P}_n$,该分布由一个(参数化/提升的)概率图模型(PGM)$\mathbb{G}$ 确定,该模型可以利用 $\mathcal{T}_n$ 提供的信息。我们所考虑的这类 PGM 使用一种多值逻辑的公式,我们称之为 $PLA^*$,其真值在单位区间 $[0, 1]$ 内。我们也使用 $PLA^*$ 来表达 $\mathbf{W}_n$ 上的查询或事件。在此设定下,我们证明,在关于 $\mathbf{T}$、$\mathbb{G}$ 以及一个(可能相当复杂的)$PLA^*$ 公式 $\varphi(x_1, \ldots, x_k)$ 的某些假设下,当 $n \to \infty$ 时,如果 $a_1, \ldots, a_k$ 是树 $\mathcal{T}_n$ 的顶点,那么 $\varphi(a_1, \ldots, a_k)$ 的值将以高概率几乎等于 $\psi(a_1, \ldots, a_k)$ 的值,其中 $\psi(x_1, \ldots, x_k)$ 是一个“简单”公式,其值总是可以快速计算(无需参考 $n$),并且 $\psi$ 本身可以仅利用定义 $\mathbf{T}$、$\mathbb{G}$ 和 $\varphi$ 的信息找到。在相同条件下,此结果的一个推论是 $PLA^*$-公式的概率收敛律。