A logical view of structured files

Structured data stored in files can benefit from standard database technology. In particular, we show here how such data can be queried and updated using declarative database languages. We introduce the notion of structuring schema, which consists of a grammar annotated with database programs. Based on a structuring schema, a file can be viewed as a database structure, queried and updated as such. For queries, we show that almost standard database optimization techniques can be used to answer queries without having to construct the entire database. For updates, we study in depth the propagation to the file of an update specified on the database view of this file. The problem is not feasible in general and we present a number of negative results. The positive results consist of techniques that allow to propagate updates efficiently under some reasonable locality conditions on the structuring schemas. Received November 1, 1995 / Accepted June 20, 1997