Schema Evolution publication categorizer

A general technique for merging database schemas is developed that
has a number
of advantages over existing techniques, the most important of which
is that schemas are
placed in a partial order that has bounded joins. This means that the
merging operation,
when it succeeds, is both associative and commutative, i.e., that the
merge of schemas
is independent of the order in which they are considered --- a
property not possessed by
existing methods. The operation is appropriate for the design of
interactive programs as it
allows user assertions about relationships between nodes in the
schemas to be considered
as elementary schemas. These can be combined with existing schemas
using precisely the
same merging operation.
The technique is general and can be applied to a variety of data
models. It can also
deal with certain cardinality constraints that arise through the
imposition of keys. A
prototype implementation, together with a graphical interface, has
been developed.