Skip to main content

two-level grammars

two-level grammars (VW-grammars, van Wijngaarden grammars) A generalization of context-free grammars that enables non-context-free aspects of a language to be specified. They were developed by A. van Wijngaarden and used in the formal definition of Algol 68. The productions of a two-level grammar are split into two parts: those in the first part are called hyperrules and act as templates for context-free productions; those in the second part are called metaproductions. The metaproductions are context-free productions and they define the set of nonterminals to be used in the hyperrules. The power of two-level grammars comes from the fact that the hyperrules can be templates for an infinite set of productions. It is in this way that they are used to define non-context-free aspects of a language.

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"two-level grammars." A Dictionary of Computing. . 24 Mar. 2019 <>.

"two-level grammars." A Dictionary of Computing. . (March 24, 2019).

"two-level grammars." A Dictionary of Computing. . Retrieved March 24, 2019 from

Learn more about citation styles

Citation styles gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, cannot guarantee each citation it generates. Therefore, it’s best to use citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

The Chicago Manual of Style

American Psychological Association

  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.