Halliday多次提到语法不确定性在语法研究中的重要性。本文在系统功能语言学的框架下,采用系统功能语言学符号视角探讨了识别小句中的歧义和重叠两类不确定特征。本文的结论是,识别小句中的歧义源自识别小句中两组结构功能的不同配置,与参与者角色有关。这类语义上的歧义可以通过语境本地化进行限制,但是不能完全消除。而重叠则源自识别小句中过程的不同体现形式,与过程角色相关。为分辨这类语法形式上的重叠,须将小句中的其他参与者角色以及环境角色同时纳入考虑范围。 Halliday repeatedly mentioned the importance of grammatical uncertainty in grammar research. Under the framework of system functional linguistics, this paper explores the ambiguity and overlap of two types of indefinite features from the perspective of system functional linguistics. The conclusion of this paper is that the ambiguities in the identification clause originate from the different configurations of the two sets of structural functions in the identification clause and are related to the role of the participants. Such semantic ambiguities can be localized by contextualization, but not completely eliminated. The overlap comes from the identification of the process of different expressions in different forms, and the role of the process. To discern the formal overlap of such grammars, other participant roles and environmental roles in the clause must be taken into account simultaneously.