Aggregation in Federated Databases: The DOK Approach

This paper addresses the design of the DOK security service allowing the enforcement of both local and federated policies. The former are those policies which relate to local databases, whereas the latter speci es the aggregation rules that govern the access to data aggregates which reside in di erent databases. In this paper we describe the component of the DOK security service which enforces the federated security policies. These security policies are de ned as aggregation constraints and are expressed as static or dynamic expressions of the FELL logic language. Static and dynamic constraints describe the combinations of transactions that must be checked against single and multiple states of a federation respectively. To enforce such constraints, transitional graphs are built to model all their sub-computations. To monitor aggregation constraints, a marking technique (called Linear Marking Technique) is designed to check the nodes and transitions of transitional graphs.