Particularly in early incarnations, transformational syntax adopted the view that phrase structure grammar must be enriched by a transformational grammar, with syntactic rules or syntactic operations that alter the base structures created by phrase structure rules. In more recent theories, including Government and Binding Theory but especially in Minimalism, the strong distinction between phrase structure and transformational components has largely been abandoned, with operations that build structure (phrase structure rules) and those that change structure (transformational rules) either interleaved, or unified under a single operation (as in the Minimalist operation Merge).