Reference grammars usually definite [BobK: sic - they mean 'define']
sentences in terms of verb types. This analysis leads them to recognize 7 varieties in the category "simple sentence"--each based on a type of verb. There's one simple sentence type that involves intransitive verbs--their S+V. Linking verbs lead to two simple sentence types: S+V+SP and S+V+A. Transitive verbs lead to 4 types--because of the 4 possibilities for different types of objects in their predicates: S+V+DO, S+V+IO+DO, S+V+O+A, S+V+DO+OP.