On structural similarity of context-free grammars
Given a grammar for translation or compiling purposes, the structure of the grammar reflects the semantics of the language rather than good parsing properties. Thus the language is often parsed with respect to another grammar, which satisfies the property that the derivation trees of the original grammar can be recovered from those of the parsing grammar. "Undercover" is introduced as a new concept for the formal treatment of such grammatical relations and properties of this relation are explored with an emphasis on decidability results and the relationship to existing concepts such as "cover" and "Reynolds cover". Some decidability questions can be related to language theoretic results on inclusion problems for simple languages.
KeywordsInclusion Problem Derivation Tree Grammatical Relation Regular Grammar Deterministic Polynomial Time
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