Grammars++ for Modelling Information in Text

Grammars provide a convenient means to describe the set of valid strings in a language, and thus they seem natural for describing the set of valid instances in a text database. It is well-known that a given language can be described by many grammars, and similarly text database designers have a choice of grammar for specifying valid documents. This flexibility can be exploited to provide information modelling capability by designing productions in the grammar to represent entities and relationships of interest to the database applications. Additional constraints can be specified by attaching predicates to selected non-terminals in the grammar. In this paper, we formalize and illustrate the use of extended grammars for text databases. When used for database definition, grammars can provide the functionality that users have come to expect of database schemas. Extended grammars can also be used to specify database manipulation, including query, update, view definition, and index specification.