The formalism for Lexical-Functional Grammar (LFG) was introduced in the 1980s as one of the first constraint-based grammatical formalisms for natural language. It has led to substantial contributions to the linguistic literature and to the construction of large-scale descriptions of particular languages. Investigations of its mathematical properties have shown that, without further restrictions, the recognition, emptiness, and generation problems are undecidable, and that they are intractable in the worst case even with commonly applied restrictions. However, grammars of real languages appear not to invoke the full expressive power of the formalism, as indicated by the fact that algorithms and implementations for recognition and generation have been developed that run—even for broad-coverage grammars—in typically polynomial time. This article formalizes some restrictions on the notation and its interpretation that are compatible with conventions and principles that have been implicit or informally stated in linguistic theory. We show that LFG grammars that respect these restrictions, while still suitable for the description of natural languages, are equivalent to linear context-free rewriting systems and allow for tractable computation.

中文翻译：

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易于理解的词汇功能语法

词法功能语法 (LFG) 的形式主义是在 1980 年代引入的，是最早的基于约束的自然语言语法形式主义之一。它对语言文学和对特定语言的大规模描述的构建做出了重大贡献。对其数学性质的研究表明，在没有进一步限制的情况下，识别、空性和生成问题是不可判定的，并且在最坏的情况下，即使有普遍应用的限制，它们也是难以处理的。然而，真实语言的语法似乎并没有充分发挥形式主义的表达能力，正如事实所表明的，识别和生成的算法和实现已经开发出来，即使是广泛覆盖的语法，也可以在典型的多项式时间内运行。本文对符号及其解释的一些限制形式化，这些限制与语言理论中隐含或非正式陈述的约定和原则兼容。我们表明，尊重这些限制的 LFG 语法虽然仍然适用于自然语言的描述，但等效于线性无上下文重写系统，并允许进行易处理的计算。