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This document defines the notion of independent views to indicate whether the range values of the two views may be achieved independently. The concepts of complementary views indicates when the domain element can be uniquely determined by the range values of the two complementary views. The relationship between independent and complementary views is considered. In unrestricted domains, a view (but not the identify or empty view) can have more than one complementary, independent view. Databases, however, are more restricted domains: They are finite power sets. A view is monotonic if it preserves inclusion. However, in finite power sets when all views are monotonic, if a given view has another view which is independent and complementary, then this view is unique.

We examine methods of implementing queries about relational databases in the case that these queries are expressed in first-order logic as a collection of Horn clauses. Because queries may be defined recursively, straightforward methods of query evaluation do not always work, and a variety of strategies have been proposed to handle subsets of recursive queries. We shall express such query evaluation techniques as 'capture rules' on a graph representing clauses and predicates. The essential property of capture rules is that they can be applied independently, thus providing a clean interface for query-evaluation systems that use several different strategies in different situations. We show how rules suggested previously can be fit into this framework, and we propose some new capture rules and generalizations of old ones. (Author)

The investigators suggest a new approach to database updates, in which a database is treated as a collection of theories. They investigate two issues: 1) equivalence of databases under update operations, b) simultaneous multiple update operations. (Author)

The query facility for their universal relation database system is now working. The fundamental paper unifying ideas on what a UR system can and should be has been published. A paper surveying developments in the field of universal relation systems was invited for the triennial IFIP Congress and was delivered in September. Some initial results on logical theories applied to the problem of updating views have been obtained. There have been a number of developments concerning inference of inclusion dependencies and on the complexity of deciding certain properties of data base schemes. Some interesting results on the difficulty of obtaining hash functions that work well for particular sets of data have been obtained and won an award. (Author)