全局性模态词与基本模态语言的扩充

Global Modality and Extension of Basic Modal Languages

模态语言是讨论关系结构的一种简洁的语言。基本模态语言是仅有一个模态算子◇的模态语言,用ML(◇)表示此语言,但基本模态语言对框架关系的表达力并不是完全的,加入新的模态算子是增强模态语言表达力的方法之一。在基本模态语言ML(◇)基础上增加全局性模态词"E"得到ML(◇,E)语言,这种更丰富的语言对关系模型和关系框架的表达力明显强于基本模态语言。

Modal languages are simple languages for talking about relational structures. The basic modal language has only one unary modal operator ◇, which was denoted as ML（◇）. Yet the basic modal language was not complete over relational structures. Adding new modalities was the way of boosting modal expressivity. Enriching basic modal language ML（◇） with global modality ＇E＇, we got language ML（◇, E）. This enriched language gained expressivity at the level of relation frames and relation models was more clear than that of the basic one,