Semantics of Database Transformations

Database transformations arise in many different settings including database integration, evolution of database systems, and implementing user views and data entry tools. This paper surveys approaches that have been taken to problems in these settings, assesses their strengths and weaknesses, and develops require ments 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 the interactions 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 briefly 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. Comments Postprint version. Published in Lecture Notes in Computer Science, Semantics in Databases, 1998, pages 55-91. Publisher URL: http://dx.doi.org/10.1007/BFb0035005 This conference paper is available at ScholarlyCommons: http://repository.upenn.edu/db_research/20 Semantics of Database Transformations Susan Davidson Peter Buneman and Anthony Kosky Dept of Computer and Information Science University of Pennsylvania Philadelphia PA Lawrence Berkeley National Laboratory Berkeley CA 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 been taken to prob lems in these settings assesses their strengths and weaknesses and develops require ments on a formal model for specifying and implementing database transformationsDatabase 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 been taken to prob lems in these settings assesses their strengths and weaknesses and develops require ments on a formal model for specifying and implementing database transformations We also consider the problem of insuring the correctness of database transforma tions In particular we demonstrate that the usefulness of correctness conditions such as information preservation is hindered by the interactions 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