Semaphore Codes and Ideals
Y.Q. Guo, G. Thierrin, S.H. Zhang · Journal of Information and Optimization Sciences · 1988
Semaphore codes over an alphabet X are closely related to the ideals of the free monoid X* generated by X and these connections are investigated in this paper. Semaphore codes are lg-dense and closed under concatenation. The set of semaphore codes can be used to characterize infix codes by using the operation of intersection of languages.