Construction Of Formal Semantic Conceptual Representation Of Primary English Modal Verbs

As a key means to express modality,modal verbs convey the speaker’s attitudes to the propositions or events being described in the utterances.However,the gradience,ambiguity and merger of English modals bring about challenges to the natural language processing and semantic studies.Therefore,the study of sense classification of modal verbs is important,and it is also of great significance to construct the formal semantic conceptual representation of primary English modal verbs.This thesis constructs the formal semantic conceptual representation of primary English modal verbs based on 5 million words corpus and Filter-APOSD approach.The senses of primary English modal verbs can,may,must,shall and will are classified into 17 categories.Then 1700 sample sentences are randomly selected from the corpus as objects and their corresponding semantic,syntactic,pragmatic,topic and genre features are extracted as attributes to construct 5 formal contexts.Firstly,the filter method is adopted to obtain the exclusive attributes to classify senses of English modal verbs.Then the attribute partial order structure diagram is used to extract complementary rules.The classification accuracy of can,may,must,shall and will reaches 95.00%,98.33%,97.67%,98.25% and 97.75% respectively,and optimal features are selected to construct the formal semantic conceptual representation of primary English modal verbs.The results of the study represent a breakthrough in the field of sense classification of English modal verbs.On this basis,this study carries out a knowledge discovery study on the relationship between modal verbs and their corresponding features.Firstly,contextual features have different categorizing functions on modal verbs,for example,pragmatic feature “speaker has authority over the subject” can effectively classify can(permission);while features like “passive voice”,“conditional clause” and “direct reporting speech” have relatively weak classifying function on can(ability).Secondly,by analyzing the formal semantic conceptual representation of epistemic modality in primary English modal verbs,it is found that among 500 sample sentences,67.40% is from informal genre texts;63.20% has stative verbs;and 50.80% has inanimate subjects,indicating that these three features could effectively classify epistemic modality.Thirdly,by comparing the formal semantic conceptual representation of primary English modal verbs,this thesis disambiguates four groups of modal verbs with subtle semantic differences: can and may(permission);can and may(possibility);must and shall(obligation);shall and will(intention),and the results suggest that contextual features such as mood,subject and pragmatic factors play a key role in resolving ambiguities.Guided by the semantics of modal auxiliaries and theory of formal concept analysis,this study describes the semantic concept of primary English modal verbs in a formalized way.The constructed formal semantic conceptual representation of primary English modal verbs provides theoretical support and practical basis for the semantic study of English modality,natural language processing as well as foreign language teaching.