scispace - formally typeset
Search or ask a question

Showing papers on "Indexed language published in 1991"


Book ChapterDOI
01 Jan 1991
TL;DR: An efficient algorithm for learning a new class of representations for formal languages defined by Smullyan's elementary formal systems for the problem of learning formal languages is demonstrated by making queries to a teacher modeled on Angluin's approach to learning k -bounded context-free grammars.
Abstract: Summary In this paper, we introduce a new class of representations for formal languages that is defined by Smullyan's elementary formal systems for the problem of learning formal languages. The class of representations is a natural extension of context-free grammars, and the languages defined by these representations lie between context-free languages and context-sensitive languages and contain some important classes of formal languages such as Angluin's pattern languages, thus enabling us to take an unified view of learning formal languages. We demonstrate an efficient algorithm for learning these representations in the framework of learning by making queries to a teacher modeled on Angluin's approach to learning k -bounded context-free grammars. Our algorithm may be viewed as a natural and powerful extension of Angluin's algorithm.

7 citations


Journal ArticleDOI
TL;DR: The right-longer (left- longer) linear grammars with the property for every production rule as natural variants of even linear gramMars defined are defined.
Abstract: This paper defines the right-longer (left-longer) linear grammars with the property for every production rule as natural variants of even linear grammars defined The relation is investigated among the language classes generated by those grammars, regular grammars, and linear context-free grammars. Also investigated are the closure properties under some basic set operations. Finally, new homomorphic characterizations are given as follows. For every recursively enumerable language L, we can find two languages L1, L2 from each pair of those language classes except a pair of even linear languages and a homomorphism h such that L=h(L1L2). For the remainder pair, a result that h(L1L2) is linear context-free is obtained.

4 citations