In the earliest stages of transformational-generative grammar, there was no lexicon and the rewrite rules and transformations aimed to generate the correct sequence of morphemes of a sentence. The introduction of the lexicon was based on empirical considerations, but not in the domain of morphology. Chomsky’s Lexicalist Hypothesis places word formation in the lexicon, but not inflection. Elaborating on these ideas, Halle (1973) lays the foundation for morpheme-based approaches and Jackendoff (1975) for word-based approaches to word formation. In Generative Semantics, semantic structure is the basis for generation and word formation is integrated with lexical insertion. Levi (1978) proposes Recoverably Deletable Predicates to restrict the power of the transformations involved in compounding.