DEDUCTIVE DATABASES FOR TRANSPORT ENGINEERING

Transport data are typical of many application areas in that they aris e from a variety of sources and are used in various ways. Furthermore, important information that is required in practical applications of t ransport databases is often not stored explicitly, but rather has to b e deduced from some that is. It is therefore natural to consider the a pplication in this field of deductive database management systems (DBM Ss). These extend traditional DBMSs by permitting the definition of in ference rules, default rules, complex data structures and integrity co nstraints, each of which can be used to provide facilities of substant ial practical value. The work described here arose from the applicatio n of a novel deductive DBMS called PFL (Persistent Functional Language ) to the storage and manipulation of road accident data. Although the primary entity type in such a database is that of an accident, queries are typically based upon the concept of a site. Because site informat ion is not stored explicitly in the database, it must be deduced from auxiliary information that provides some indication of location. The c ombination of large amounts of data and computationally intensive quer ies presents extraordinary demands for the database system and has led to the development of new software techniques of high efficiency in b oth computation and data manipulation.