Text typing is the classification of text according to the purpose of the author. There is no universally recognised register of types: the four distinguished here are descriptive, narrative, persuasive or instructional. Type is assigned by analysing the clausal structure of the discourse and certain semantic features within the text such as theme of sentence, modality of verb, and process type (i.e. whether the verbal group is material, mental, relational, behavioural, verbal or existential). The ability to discriminate textual genre is an important step in the evaluation and classification of documents.