Although missing (or null) values are found in most data bases they are not formally recognized by existing DBMS. The correct manipulation of those values is then left to the applications programs. This paper extends and formalizes a model suggested by Codd (4) for the explicit recognition of missing values by the relational algebra. It also explores the implications of the model and discusses ...

We review the applications of structured expert judgment uncertainty quantification using the "classical model" developed at the Delft University of Technology over the last 17 years (Cooke, 1991). These involve 45 expert panels, performed under contract with problem owners who reviewed and approved the results. With a few exceptions, all these applications involved the use of seed variables; t...

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We develop an algorithm for inverting gravity data to construct estimates of the base of salt and investigate the sensitivity of the recovered model to four different sources of errors. The inversion algorithm is based on the approach of Tikhonov regularization.The prior information is typically shape and depth of the top salt and of a known part of base salt from seismic image. The error in su...

The structure of data to be stored by a Data Base Management System (DBMS) is usually decided by a database administrator. Individual users and applications are generally interested in only a subset of the data stored in the database. Often, they wish to see this subset structured in a way which reflects their particular needs. Since it is not generally possible to structure a database so as to...

Data b a s e s a c c e s s i s t y p i c a l l y approached as a prog~anmi n g problem r a t h e r t han a u s e r i n t e r f a c e problem. Wez. conseq e n t l y see s i t u a t i o n s where on ly programmers can a c c e s s i n f o r m a t i o n i n d a t a b a s e s , i n s p i t e o f the f a c t t h a t t h e peop le who need t h i s i n f o r m a t i o n a re t y p i c a l l y n o n p r...

In this paper we discuss how we see the capabilities of DBMSs evolving over the next several years to meet the needs of expert data base applications. We also present some of the research thrusts which we see as important that appear to be receiving insufficient attention in the research community.

In this thesis we introduce and solve three privacy problems in Secure Database Access protocols: Database Privacy, the Data Replication Problem, and the Secure user Identity problem. Database Privacy is concerned with keeping the databases information secure from the user. The Data Replication problem (DRP) deals with a new security concern for databases that emanates from the need to replicat...

This paper proposes extensions to a relational database system to support the selection and execution of algorithms for shortest path search problems. An expert system can employ this extended DBMS to provide unified management of data and part of the knowledge base. Several search algorithms have been prototyped using the database extensions. Their performance characteristics are described and...