4 research outputs found
Nonterminal complexity of tree controlled grammars
This paper studies the nonterminal complexity of tree controlled grammars. It is proved that the number of nonterminals in tree controlled grammars without erasing rules leads to an infinite hierarchy of families of tree controlled languages, while every recursively enumerable language can be generated by a tree controlled grammar with erasing rules and at most nine nonterminals
Strictly Locally Testable and Resources Restricted Control Languages in Tree-Controlled Grammars
Tree-controlled grammars are context-free grammars where the derivation
process is controlled in such a way that every word on a level of the
derivation tree must belong to a certain control language. We investigate the
generative capacity of such tree-controlled grammars where the control
languages are special regular sets, especially strictly locally testable
languages or languages restricted by resources of the generation (number of
non-terminal symbols or production rules) or acceptance (number of states).
Furthermore, the set theoretic inclusion relations of these subregular language
families themselves are studied.Comment: In Proceedings AFL 2023, arXiv:2309.0112
On Normal Forms and Erasing Rules in Path Controlled Grammars
This paper discusses path controlled grammars—context-free gram- mars with a root-to-leaf path in their derivation trees restricted by a control language. First, it investigates the impact of erasing rules on the generative power of path controlled grammars. Then, it establishes two Chomsky-like normal forms for path controlled grammars—the first allows unit rules, the second allows just one erasing rule