A temporal object-oriented model and query language that supports the modeling and manipulation of complex temporal or versioned objects is developed. The authors show that the approach not only provides a richer model than the relational for capturing the semantics of complex temporal objects, but also requires no special constructs in the query language. Consequently, the retrieval of temporal and non-temporal information is uniformly expressed. By allowing variables and quantifiers to range over time, can be formulated that require special operators in other languages. Temporal aggregation queries, which are not easily expressed in other models, are expressed using the same aggregation operators as for nontemporal data.>

A new indexing technique, time index, for improving the performance of certain classes of temporal queries was previously described by the author (see The 16th Conference on Very Large Databases (1990)). Three variations for implementing the time index efficiently are proposed and the performance of these three variations is compared with the performance of the original time index. Various parameters such as average lifetime of a version, average number of versions per object, block size and block clustering, and query time interval length are discussed. Simulation results show how these parameters affect the performance of the various implementation variations for the time index.>

A temporal extension to an extended ER (entity-relationship) model is proposed. The concept of life span for entities and relationships is incorporated in the ER model. Also specified is a temporal query and update language which is an extension of the GORDAS language. The concepts of temporal Boolean expressions, temporal selection, and temporal projection are introduced, and their use in the query language is illustrated. Temporal constraints are incorporated into the ER model, and the semantics of temporal update operations is defined.>

Detecting a nonexistent deadlock in distributed systems has been referred to as false deadlock detection. This correspondence shows that false deadlock wi1l never occur in a system of two-phase locking transactions. We also describe an algorithm to avoid false deadlock detection when transactions are not two-phase locking.

We propose efficient algorithms to maintain a replicated dictionary using a log in an unreliable network. A non-serializable approach is used to achieve high concurrency. The solutions are resilient to both node and communication failures. Optimizations are developed for networks which are not completely connected.