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In two previous works [74CGP,86CGP], we defined and studied a scheme for grammar-based generation of planar maps, using deterministic parallel (in the sense of Lindenmayer) derivation rules of tow types — binary splitting of countries (fission) and binary merging (fusion). Countries would be visualized as cells in applications to modeling the development of (planar) biological organisms, for example...
A superAFL is a family of languages closed under union with unitary sets, intersection with regular sets, and nested iterated substitution and containing at least one nonunitary set. Every superAFL is a full AFL containing all context-free languages. If L is a full principal AFL, then S∞(L, the least superAFL containing L, is full principal. If L is not substitution closed, the substitution closure...
By generalizing the notions of a one counter machine and of a finite turn pushdown store automaton, it is possible to define an omega 2-hierarchy of families of context-free languages such that each subfamily is infinite, closed under union, concatenation and closure, homomorphism, intersection with regular sets and inverse homomorphism and reversal. Each subfamily can be characterized in a manner...
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