Abstract

It is known that ℷ a can be generated by a node-label-controlled (NLC) graph grammar, ß a cannot be generated by NLC graph grammars, and ℷ a cannot be generated by boundary NLC (BNLC) graph grammars, where ℷ a is the set of all graphs labeled by the single label a and ß a is the set of all cycle graphs labeled by the single label a. In this paper, we consider the class L c of all graph languages including ß a . We show that the class L c and the class of BNLC graph languages are mutually disjoint. Furthermore, we provide a new simple graph language that can be generated by an NLC graph grammar but cannot be generated by BNLC graph grammars using a method different from Rozenberg and Welzl.

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