Transaction processing is an established technique for the concurrent and fault tolerant access of persistent data. While this technique has been successful in standard database systems, factors such as time-critical applications, emerg ing technologies, and a re-examination of existing systems suggest that the performance, functionality and applicability of transactions may be substan tially enhanced if temporal considerations are taken into account. That is, transactions should not only execute in a "legal" (i.e., logically correct) man ner, but they should meet certain constraints with regard to their invocation and completion times. Typically, these logical and temporal constraints are application-dependent, and we address some fundamental issues for the man agement of transactions in the presence of such constraints. Our model for transaction-processing is based on extensions to established mod els, and we briefly outline how logical and temporal constraints may be ex pressed in it. For scheduling the transactions, we describe how legal schedules differ from one another in terms of meeting the temporal constraints. Exist ing scheduling mechanisms do not differentiate among legal schedules, and are thereby inadequate with regard to meeting temporal constraints. This provides the basis for seeking scheduling strategies that attempt to meet the temporal constraints while continuing to produce legal schedules."

The desire and the necessity for accessing and processing information stored in computer networks anytime and anywhere' has been the impetus for the growing interest in mobile computing research. Wired computing networks and end devices such as PCs and workstations have effectively extended the data-only networking capability of a few years ago to sophisticated multimedia networking. The cost of such transformation to the end user turns out to be very nominal. Undoubtedly the wireless access technology has given a big boost to mobile cellular telephony and data networking. Processing general purpose multimedia information requires, besides higher bandwidth, means for controlling the available bandwidth and caring for quality of service issues. This problem is accentuated by the need for providing such service in the presence of wireless physical layer and host mobility. Thus, tetherless and ubiquitous mobile and wireless computing systems should carefully combine advances in computer networking and wireless communication. While several experimental mobile computing platforms have sprung up, much research is needed to overcome technological obstacles in low power system design, sustainable battery life, unreliability and limited bandwidth of the wireless channel. Mobile Computing addresses some aspects of this new but rapidly growing field of research. A total of eight papers span the areas of protocols, network architecture, and performance issues. All of the papers deal with the complexities of host mobility in a wireless setting. They expose several challenges that affect system design of mobile computing networks at various levels. By addressing these challenges in an efficient and cost-effective manner, it is hoped that user-friendly, seamless and faster networks will emerge to serve the sophisticated and demanding applications of mobile users. Mobile Computing serves as an excellent reference, providing insights into some of the most important issues in mobile and wireless computing.

Transaction processing is an established technique for the concurrent and fault tolerant access of persistent data. While this technique has been successful in standard database systems, factors such as time-critical applications, emerg ing technologies, and a re-examination of existing systems suggest that the performance, functionality and applicability of transactions may be substan tially enhanced if temporal considerations are taken into account. That is, transactions should not only execute in a "legal" (i.e., logically correct) man ner, but they should meet certain constraints with regard to their invocation and completion times. Typically, these logical and temporal constraints are application-dependent, and we address some fundamental issues for the man agement of transactions in the presence of such constraints. Our model for transaction-processing is based on extensions to established mod els, and we briefly outline how logical and temporal constraints may be ex pressed in it. For scheduling the transactions, we describe how legal schedules differ from one another in terms of meeting the temporal constraints. Exist ing scheduling mechanisms do not differentiate among legal schedules, and are thereby inadequate with regard to meeting temporal constraints. This provides the basis for seeking scheduling strategies that attempt to meet the temporal constraints while continuing to produce legal schedules."