Closure properties of pattern languages Joel Day Daniel Reidenbach Markus L. Schmid 2134/22205 https://repository.lboro.ac.uk/articles/journal_contribution/Closure_properties_of_pattern_languages/9401654 Pattern languages are a well-established class of languages, but very little is known about their closure properties. In the present paper we establish a large number of closure properties of the terminal-free pattern languages, and we characterise when the union of two terminal-free pattern languages is again a terminal-free pattern language. We demonstrate that the equivalent question for general pattern languages is characterised differently, and that it is linked to some of the most prominent open problems for pattern languages. We also provide fundamental insights into a well-known construction of E-pattern languages as unions of NE-pattern languages, and vice versa. 2016-08-05 08:49:41 Pattern languages Closure properties Computation Theory and Mathematics Information and Computing Sciences not elsewhere classified Distributed Computing