Last modified: 05-Jul-07.

An *imperative adaptive grammar* model is a grammar model in which
the explicit manipulation of rule sets is accomplished by imperative means
(as opposed to
declarative; see
What is an adaptive grammar? ).
That is, the rule set is varied over time during parsing:
the set of rules available to expand a given instance of a nonterminal
depends necessarily on *when* it is expanded
(not just on *where* that instance occurs in the syntax tree).

Because of this time-dependence, imperative adaptive grammars generally have a global internal state, typically just the set of production rules. Consequently, they have configurations, in the same sense that an automaton has configurations. The derivation relation of an imperative adaptive grammar often bears a striking resemblance to the computation relation of an automaton. See What is a grammar?.

Here is a list of some imperative adaptive grammar models I know about. I've written HTML summaries of the ones I understand, and most of them are discussed at greater length in my Master's thesis. (Some other, more recent models are mentioned in the Wikipedia article "Adaptive grammar".)

- ECFGs (Extensible Context-Free Grammars). Ben Wegbreit, 1970.
- DTTs (Dynamic Template Translators). K. P. Mason, 1984.
- Modifiable Grammars. Boris Burshteyn, 1990.