Schema Evolution and Integration

Abstract. Providing support for schema evolution allows existing databases to be adjusted for varying roles over time. This paper reflects on existing evolution support schemes and introduces a more general and functional mechanism tosupport schema evolution and instance adaptation for centralized and distributed object-oriented database systems. Our evolution support scheme is distinguished from previous mechanisms in that it is primarily concerned with preserving existing database objects and maintaining compatibility for old applications, while permitting a wider range of evolution operations. It achieves this by supporting schema versioning, allowing multiple representations of instances to persist simultaneously, and providing for programmer specification of how to adapt existing instances. The mechanism is general enough to provide much of the support necessarily for heterogeneous schema integration, as well as incorporating much of the features of object migration and replication

Land and water governance on the shores of the Laurentian Great Lakes

© 2014 International Water Resources Association. The Laurentian Great Lakes Basin is large and complex, as is its institutional setting. Given these characteristics, Great Lakes boundaries are both horizontal and fluid, and governance at the Great Lakes water/land interface implicates at least four different frontiers of planning and management. While substantial multinational and sub-national policy regimes have formed over the last century to improve Great Lakes water quantity and water quality management, parallel arrangements have not formed to manage better shoreland boundaries and frontiers