Abstract
A semi-conditional grammar is a form of regulated rewriting system. Each rule consists of a context-free core rule \(A\rightarrow w\) and two strings \(w_+,w_-\); the rule is applicable if \(w_+\) (the positive condition) occurs as a substring of the current sentential form, but \(w_-\) (the negative condition) does not. The maximum lengths i, j of the positive or negative conditional strings, respectively, give a natural measure of descriptional complexity, known as the degree of such grammars. Employing several normal form results on phrase-structure grammars as derived by Geffert, we improve on previously obtained results by reducing the number of nonterminals of semi-conditional grammars of a given degree (i, j) while maintaining computational completeness of the said mechanisms.
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Notes
- 1.
We collect all rules \(S\rightarrow w\) with \(S\notin sub (w)\) plus the only rule \(S\rightarrow uS\) within \(P_{cf}\).
- 2.
Some details are suppressed due to space constraints.
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Fernau, H., Kuppusamy, L., Oladele, R.O. (2018). New Nonterminal Complexity Results for Semi-conditional Grammars. In: Manea, F., Miller, R., Nowotka, D. (eds) Sailing Routes in the World of Computation. CiE 2018. Lecture Notes in Computer Science(), vol 10936. Springer, Cham. https://doi.org/10.1007/978-3-319-94418-0_18
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