Specification and management of interdependent data in operational systems and data warehouses

(Inter)Dependent objects include data replicated or cached in multiple database systems, data collected and summarized in data warehouses for analysis, planning, and decision support, as well as any other category of objects whose states are related and they are maintained in different information systems. In this paper we discuss dependencies between objects in an environment consisting of operational systems and a data warehouse, and describe their specification and enforcement. To specify object dependencies we introduce Object Dependency Descriptors (ObjectDDs). These describe the relationships between dependent objects, and define how much inconsistency between original objects and their replicas/collections/summaries can be tolerated before it is necessary to restore their consistency. Object dependencies are enforced by extended transactions designed specifically for evaluating if dependent objects satisfy their specified relationships, evaluating whether possible inconsistencies can be tolerated, and (if not) restoring consistency. To describe the transactional behavior of such consistency evaluation and restoration transactions we use Transaction Dependency Descriptors (TransactionDDs). TransactionDDs define the transactional relationships between consistency evaluation and restoration (asynchronous) transactions, as well as the relationships between such asynchronous transactions and regular (synchronous) transactions executed directly by applications. To automatically maintain the consistency of dependent objects, we propose the concept of a Dependency Management System (DMS). A DMS monitors dependent objects, evaluates object consistency, and schedules and controls consistency restoration transactions to keep dependent objects within acceptable consistency levels. We describe key components in the DMS architecture, and a relatively simple implementation involving straightforward extensions in a relational DBMS.