Relations And Attributes - A Symbiotic Basis For Editing Environments

The ability to generate language-based editors depends on the existence of a powerful, language-independent model of editing. A model is proposed in which programs are represented as attributed abstract-syntax trees with an associated relational database. Relations can depend on the state of the attributed tree, and attributes can depend on the values in relations, provided there are no circular dependencies. The power and the limitations of relational operations are demonstrated with respect to the support of static-semantic checking, anomaly detection, an interrogation facility, and the ability to define alternate views of a program. The advantages of the hybrid system over both the purely relational and purely attribute-based systems are presented, and a prototype implementation of an editor generator is discussed. New algorithms are given for query evaluation and incremental view updating motivated by the efficiency requirements of interactive editing under the defined model.