The effects of station buffer capacity on the performance of token-ring networks are investigated. The network is modeled as a multi-queue system with a single cyclic server, one finite buffer queue and an arbitrary number of infinite buffer queues, a nonexhaustive service discipline, constant station walking time, Poisson arrival processes, and general message service time distributions. For the particular cases of exponentially distributed and constant message service times, approximate average message delays for both the finite and infinite buffer stations and the probability of message blocking at the finite buffer station are given in explicit expressions. Several numerical results are presented. Interesting conclusions are obtained from comparing network performance in the case when the network traffic load is completely balanced with the case when the finite buffer station is much more heavily loaded than the individual infinite buffer stations.>

The performance of token-passing systems with limited service and Poisson arrivals is investigated. For pure Poisson arrivals, a Laplace-Stieltjes transform (LST) of an approximate customer/packet waiting time distribution is derived and expressed as a functional equation, from which the approximate mean and the variance of waiting time are obtained; for batch Poisson arrivals, an approximate mean of waiting time is derived. Mean waiting time approximations are compared against both simulation results and other results presented in the literature, while the variance approximation is evaluated by comparing it to simulation results only since no other results on variance have been reported so far. As application examples of the analytical results, multimedia file transfers over token-passing LANs are modeled and studied.>

Office-by-Example (OBE) is an integrated office information system that has been under development at IBM Research. OBE, an extension of Query-by-Example, supports various office features such as database tables, word processing, electronic mail, graphics, images, and so forth. These seemingly heterogeneous features are integrated through a language feature called example elements . Applications involving example elements are processed by the database manager, an integrated part of the OBE system. In this paper we describe the facilities and architecture of the OBE system and discuss the techniques for integrating heterogeneous objects.