Directed Random Generation of Sentences The problem of producing sentences of a transformational grammar by using a random generator to create phrase structure trees for input to the lexical insertion and transformational phases is discussed. A purely random generator will produce base trees which will be blocked by the transformations, and which are frequently too long to be of practical interest. A solution is offered in the form of a computer program which allows the user to constrain and direct the generation by the simple but powerful device of restricted subtrees. The program is a directed random generator which accepts as input a subtree with restrictions and produces around it a tree which satisfies the restrictions and is ready for the next phase of the grammar. The underlying linguistic model is that at Noam Chomsky, as presented in Aspects of the Theory of Syntax. The program is written in FORTRAN IV for the IBM 360/67 and is part of a unified computer system for transformational grammar. It is currently being used with several partial grammars of English. CACM January, 1969 Friedman, J. transformational grammar, natural language syntax, language processing, sentence generation, computational linguistics, syntax 3.42 CA690110 JB February 20, 1978 11:44 AM 1030 4 1939 1261 4 1939 1886 4 1939 1939 4 1939 1939 4 1939 1030 5 1939 1939 5 1939 1939 5 1939 1939 5 1939 2767 5 1939 3064 5 1939 678 5 1939 1846 6 1939 1939 6 1939 1939 6 1939 2742 6 1939 2767 6 1939 2936 6 1939