Abstract. Database transformations arise in many di erent settings including database integration, evolution of database systems, and implementing user views and data-entry tools. This paper surveys approaches that have beentaken to problems in these settings, assesses their strengths and weaknesses, and develops requirements on a formal model for specifying and implementing database transformations. We also consider the problem of insuring the correctness of database transformations. In particular, we demonstrate that the usefulness of correctness conditions such as information preservation is hindered by theinteractions of transformations and database constraints, and the limited expressive power of established database constraint languages. We conclude that more general notions of correctness are required, and that there is a need for a uniform formalism for expressing both database transformations and constraints, and reasoning about their interactions. Finally we introduce WOL, a declarative language for specifying and implementing database transformations and constraints. We brie y describe the WOL language and its semantics, and argue that it addresses many of the requirements on a formalism for dealing with general database transformations. 1

Contents 1 Introduction 4 1.1 Thesis Overview : : : : : : : : : : : : : : : : : : : : : : : : : : : 4 1.2 Object Oriented Databases : : : : : : : : : : : : : : : : : : : : : 6 1.3 Composite Objects : : : : : : : : : : : : : : : : : : : : : : : : : 7 1.4 Historical Information in Databases : : : : : : : : : : : : : : : : 9 2 The LINCKS System 11 2.1 Objects in the LINCKS System : : : : : : : : : : : : : : : : : : 11 2.2 Composite Objects in the LINCKS System : : : : : : : : : : : : 13 2.3 Historical Information of Objects in LINCKS : : : : : : : : : : : 15 2.3.1 Temporal History : : : : : : : : : : : : : : : : : : : : : : 15 2.3.2 Edit History : : : : : : : : : : : : : : : : : : : : : : : : : 17 2.3.3 Use of History : : : : : : : : : : : : : : : : : : : : : : : : 19 3 LITE as Temporal Fr

Query languages and their optimizations have been a very important issue in the database community. Languages for updating databases, however, have not been studied to the same extent, although they are clearly important since databases must change over time. The structure and expressiveness of updates is largely dependent on the data model. In relational databases, for example, the update language typically allows the user to specify changes to individual fields of a subset of a relation that meets some selection criterion. The syntax is terse, specifying only the pieces of the database that are to be altered. Because of its simplicity, most of the optimizations take place in the internal processing of the update rather than at the language level. In complex value databases, the need for a terse and optimizable update language is much greater, due to the deeply nested structures involved. Starting with a query language for complex value databases called the Collection Programming Lang...