Unification grammars and off-line parsability

Efrat Jaeger, Nissim Francez, Shuly Wintner

Research output: Contribution to journalArticlepeer-review


Unification grammars are known to be Turing-equivalent; given a grammar G and a word w, it is undecidable whether w L(G). In order to ensure decidability, several constraints on grammars, commonly known as off-line parsability (OLP), were suggested, such that the recognition problem is decidable for grammars which satisfy OLP. An open question is whether it is decidable if a given grammar satisfies OLP. In this paper we investigate various definitions of OLP and discuss their interrelations, proving that some of the OLP variants are indeed undecidable. We then present a novel, decidable OLP constraint which is more liberal than the existing decidable ones.

Original languageEnglish
Pages (from-to)199-234
Number of pages36
JournalJournal of Logic, Language and Information
Issue number2
StatePublished - Mar 2005

Bibliographical note

Funding Information:
The work of Nissim Francez was partially funded by the Vice-President’s fund for the promotion of research at the Technion. The work of Shuly Wintner was supported by the Israeli Science Foundation (grant no. 136/01).


  • Off-line parsability
  • Parsing termination
  • Unification grammars

ASJC Scopus subject areas

  • Computer Science (miscellaneous)
  • Philosophy
  • Linguistics and Language


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