Context-free languages can be characterized in several ways. This article studies projective linearisations of languages of simple dependency trees, i.e., dependency trees in which a node can govern at most one node with a given syntactic function. We prove that the projective linearisations of local languages of simple dependency trees coincide with the context-free languages. Simple dependency trees suggest alternative dual notions of locality and projectivity, which permits defining a dual language for each context-free language. We call this new class of languages anti-context-free. These languages are related to some linguistic constructions exhibiting the so-called cross-serial dependencies that were historically important for the development of computational linguistics. We propose that this duality could be a relevant linguistic phenomenon.

中文翻译：

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反上下文无关语言

上下文无关语言可以通过多种方式来表征。本文研究简单依存树语言的投影线性化，即依存树中一个节点最多可以通过给定的句法函数管理一个节点。我们证明简单依赖树的本地语言的投影线性化与上下文无关语言一致。简单的依赖树提出了局部性和投影性的替代双重概念，这允许为每种上下文无关语言定义双重语言。我们称这种新的语言为反上下文无关的。这些语言与一些表现出所谓的跨序列依赖关系的语言结构有关，这些依赖关系在历史上对计算语言学的发展非常重要。我们认为这种二元性可能是一种相关的语言现象。