Cellular Graph Acceptors, 5: Closure Properties of Cellular d-Graph Languages.
Angela Y. Wu · 1978
Cellular d-graph languages are shown to be closed under set theoretic operations, including finite union and intersection; and under geometric operations, including permutation of arc end numbering, concatenation, closure, and formation of line graphs. Determinism is preserved under the set-theoretic operations; but under the geometric operations, determinism is known to be preserved only when the languages are also predicates. (Author)