2级可折叠下推图是树自动图
Collapsible Pushdown Graphs of Level 2 are Tree-Automatic
摘要：
我们表明，可折叠的下推系统的水平2生成的图形是树自动的。即使当我们允许$ε$ -收缩并为配置对添加可达性谓词（带有常规约束）时，结构仍然是树自动的。因此，他们的FO理论是可判定的，即使是通过可达性谓词扩展。作为一个推论，我们得到的树自动化的第二层的高加索层次。
英文摘要：
We show that graphs generated by collapsible pushdown systems of level 2 are tree-automatic. Even when we allow $ε$-contractions and add a reachability predicate (with regular constraints) for pairs of configurations, the structures remain tree-automatic. Hence, their FO theories are decidable, even when expanded by a reachability predicate. As a corollary, we obtain the tree-automaticity of the second level of the Caucal-hierarchy.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
