NUL: a Navigational User's Language for a network structured data base
SIGMOD '76 Proceedings of the 1976 ACM SIGMOD international conference on Management of data
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A generalized high level query language has been developed for use with a network data base, as defined by the CODASYL DBTG report. Of particular interest is the capability of manipulating graphical entities with this language. The system was developed to supportan offshore oil lease information project where one must formulate queries pertaining to proximity of graphical entities. To facilitate such requests new relational operators were defined and implemented. Thus compound Boolean expressions can be formed which involve graphical as well as non-graphical criteria. Since one goal of the information system is to produce selectively colored maps via an FR80 microfilm recorder, the query language syntax provides the user with a comprehensive thematic cartography capability. The query language is designed to isolate the user from the underlying network structure of the data base. In order to accomplish this generalized pathfinding and accessing algorithms had to be developed. Pathfinding is facilitated through an adjacency matrix involving all record types in the data base, while accession is controlled by examining the local owner-member relation for current record types. Besides querying, the system provides the usual complement of data base management system functions, i.e. deletion, updating, reporting, etc.