Semantics--based Multilevel Transaction Management in Federated Systems

A federated database management system (FDBMS) is a special type of distributed database system that enables existing local databases, in a heterogeneous environment, to maintain a high degree of autonomy. One of the key problems in this setting is the coexistence of local transactions and global transactions, where the latter access and manipulate data of multiple local databases. In modeling FDBMS transaction executions we propose a more realistic model than the traditional read/write model; in our model a local database exports high--level operations which are the only operations distributed global transactions can execute to access data in the shared local databases. Such restrictions are not unusual in practice as, for example, no airline or bank would ever permit foreign users to execute ad hoc queries against their databases for fear of compromising autonomy. The proposed architecture can be elegantly modeled using the multilevel nested transaction model for which a sound theore..