LR-PARSING DERIVED

AbstractThe LR(k)-parsing algorithm is derived, i.e., presented and proved as an interplay between program development and parsing theory. The program development uses invariants and the new concept of weakest angelic precondition. The parsing theory involved relates rightmost derivability to three other transitive relations on strings. The usual stack of item sets and the finite automaton appear in an optimisation of the abstract algorithm

A Short Description of a Translator-Writing System (BOBS-System)

The paper itself is an abstract describing a translator-writing-system called the BOBS-System, which is an implementation of some of the ideas in the Ph. D. thesis of De Remer. This thesis describes closely the parsing techniques for the hierarchy of LR(k)-grammars. The main parts of the BOBS-System is described without many details

Probabilistic parsing strategies.

Abstract. We present new results on the relation between purely symbolic context-free parsing strategies and their probabilistic counterparts. Such parsing strategies are seen as constructions of pushdown devices from grammars. We show that preservation of probability distribution is possible under two conditions, viz. the correct-prefix property and the property of strong predictiveness. These results generalize existing results in the literature that were obtained by considering parsing strategies in isolation. From our general results, we also derive negative results on so-called generalized LR parsing

Simple chain grammars

A subclass of the LR(0)-grammars, the class of simple chain grammars is introduced. Although there exist simple chain grammars which are not LL(k) for any k, this new class of grammars is very close related to the class of LL(1) and simple LL(1) grammars. In fact it can be proved (not in this paper) that each simple chain grammar has an equivalent simple LL(1) grammar. A very simple (bottom-up) parsing method is provided. This method follows directly from the definition of a simple chain grammar and can easily be given in terms of the well-known LR(0) parsing method

Probabilistic Parsing Strategies

We present new results on the relation between purely symbolic context-free parsing strategies and their probabilistic counter-parts. Such parsing strategies are seen as constructions of push-down devices from grammars. We show that preservation of probability distribution is possible under two conditions, viz. the correct-prefix property and the property of strong predictiveness. These results generalize existing results in the literature that were obtained by considering parsing strategies in isolation. From our general results we also derive negative results on so-called generalized LR parsing.Comment: 36 pages, 1 figur