Adaptive grammar

An adaptive grammar is a formal grammar that explicitly provides mechanisms within the formalism to allow its own production rules to be manipulated. John N. Shutt defines adaptive grammar as a grammatical formalism that allows rule sets (aka sets of production rules) to be explicitly manipulated within a grammar. Types of manipulation include rule addition, deletion, and modification. The first description of grammar adaptivity (though not under that name) in the literature is generally taken to be in a paper by Alfonso Caracciolo di Forino published in 1963. The next generally accepted reference to an adaptive formalism (extensible context-free grammars) came from Wegbreit in 1970 in the study of extensible programming languages, followed by the dynamic syntax of Hanford and Jones in 1973. Until fairly recently, much of the research into the formal properties of adaptive grammars was uncoordinated between researchers, only first being summarized by Henning Christiansen in 1990 in response to a paper in ACM SIGPLAN Notices by Boris Burshteyn. The Department of Engineering at the University of São Paulo has its Adaptive Languages and Techniques Laboratory, specifically focusing on research and practice in adaptive technologies and theory. The LTA also maintains a page naming researchers in the field. While early efforts made reference to dynamic syntax and extensible, modifiable, dynamic, and adaptable grammars, more recent usage has tended towards the use of the term adaptive (or some variant such as adaptativa, depending on the publication language of the literature). Iwai refers to her formalism as adaptive grammars, but this specific use of simply adaptive grammars is not typically currently used in the literature without name qualification. Moreover, no standardization or categorization efforts have been undertaken between various researchers, although several have made efforts in this direction. Shutt categorizes adaptive grammar models into two main categories: Jackson refines Shutt's taxonomy, referring to changes over time as global and changes over space as local, and adding a hybrid time-space category: