On Alternating Non-Context-Free Grammars
نویسنده
چکیده
We study several extensions of the notion of alternation from context-free grammars to context-sensitive and arbitrary phrase-structure grammars. Thereby new grammatical characterizations are obtained for the class of languages that are accepted by alternating pushdown automata.
منابع مشابه
On state-alternating context-free grammars
The state-alternating context-free grammars are introduced, and the language classes obtained from them are compared to the classes of the Chomsky hierarchy as well as to some well-known complexity classes. In particular, the state-alternating context-free grammars are compared to the alternating context-free grammars of Moriya (1989) and to the alternating pushdown automata. Further, various d...
متن کاملAlternating Regular Tree Grammars in the Framework of Lattice-Valued Logic
In this paper, two different ways of introducing alternation for lattice-valued (referred to as {L}valued) regular tree grammars and {L}valued top-down tree automata are compared. One is the way which defines the alternating regular tree grammar, i.e., alternation is governed by the non-terminals of the grammar and the other is the way which combines state with alternation. The first way is ta...
متن کاملAlternating Context-Free Languages and Linear Time mu-Calculus with Sequential Composition
This paper shows that linear time μ-calculus with sequential composition defines exactly those properties that are expressible with alternating context-free grammars for ω-words. This helps to understand the expressive power of modal μ-calculus with a chop operator and provides a logical characterisation of the class of alternating context-free languages.
متن کاملOn the Complexity of Szilard Languages of Regulated Grammars
We investigate computational resources used by alternating Turing machines (ATMs) to accept Szilard languages (SZLs) of regulated rewriting grammars. The main goal is to relate these languages to lowlevel complexity classes such asNC1 andNC2. We focus on the derivation process in random context grammars (RCGs) with context-free rules. We prove that unrestricted SZLs and leftmost-1 SZLs of RCGs ...
متن کاملStudying impressive parameters on the performance of Persian probabilistic context free grammar parser
In linguistics, a tree bank is a parsed text corpus that annotates syntactic or semantic sentence structure. The exploitation of tree bank data has been important ever since the first large-scale tree bank, The Penn Treebank, was published. However, although originating in computational linguistics, the value of tree bank is becoming more widely appreciated in linguistics research as a whole. F...
متن کامل