Sandra A. Mamrak

Gaining efficiency in transport services by appropriate design and implementation choices

End-to-end transport protocols continue to be an active area of research and development involving (1) design and implementation of special-purpose protocols, and (2) reexamination of the design and implementation of general-purpose protocols. This work is motivated by the perceived low bandwidth and high delay, CPU, memory, and other costs of many current general-purpose transport protocol designs and implementations. This paper examines transport protocol mechanisms and implementation issues and argues that general-purpose transport protocols can be effective in a wide range of distributed applications because (1) many of the mechanisms used in the special-purpose protocols can also be used in general-purpose protocol designs and implementations, (2) special-purpose designs have hidden costs, and (3) very special operating system environments, overall system loads, application response times, and interaction patterns are required before general-purpose protocols are the main system performance bottlenecks.

The Distributed Double-Loop Computer Network (DDLCN)

This paper presents the design of the Distributed Double-Loop Computer Network (DDLCN), which is a local-area distributed computing system that interconnects midi, mini and micro computers using a fault-tolerant double-loop network. Several new features and novel concepts have been incorporated into the design of its subsystems, viz., the reliable communication network, the programming/operating system (P/OS), and the distributed loop data base system (DLDBS). The interface design is unique in that it employs tri-state control logic and bit-sliced processing, thereby enabling the network to become dynamically reconfigurable and fault tolerant with respect to communication link failure as well as component failure in the interface. Three classes of multi-destination communication protocols, each providing a different degree of reliability, have been incorporated into the network to facilitate efficient and reliable exchanges of messages. The P/OS is distinguished from other similar research efforts in that its ultimate goal is to support not only communication and cooperation among autonomous, distributed processes running at various nodes, but also to support convenient and correct resource sharing through program generation (semi-automatic programming) for application and systems programmers. A new concurrency control mechanism for DLDBS has been developed, which uses distributed control without global locking and is deadlock free. In addition to being simple to implement and having good performance (high throughput and low delay), the mechanism is also robust with respect to failure of both communication links and hosts.

Chameleon: a system for solving the data-translation problem

A comprehensive data translation system is described with the following characteristics: (1) it is derived from a formal model of the translation task; (2) it supports the building of translation tools; (3) it supports the use of translation tools; and (4) it is accessible to its targeted end users. A software architecture to achieve the translation capability is fully implemented. Translators have been generated using the architecture, both by the original software developers and by industrial associates who have installed the architecture at their own sites. >

Presurgical serum albumin levels predict survival time from glioblastoma multiforme.

To determine whether serum albumin levels, before first surgery, predict time until death, 24 glioblastoma multiforme patients newly diagnosed at Ohio State University and Cleveland Clinic Foundation Hospitals between 1993 and 1995 were followed until 1996. Patients with presurgical serum albumin levels below 3.4 mg/dL survived an average (median) of 62 days (95% confidence interval (CI): 34, 135 days) after surgery. Those with serum albumin levels of at least 3.4 mg/dL survived an average of 494 days (95% CI: 241, 624 days). The association between serum albumin level and time until death persists when adjusted for demographic and treatment variables using Cox proportional hazards regression. Adjusted hazard ratios, by quartile of presurgical serum albumin level, are: 1.0, 1.2, 0.1, 0.1 (P-value for trend test=0.007). In addition to providing a prognostic indicator, presurgical serum albumin levels can be used to evaluate the success of randomization of clinical trials for glioblastoma multiforme therapies. Our findings are consistent with results seen for tumors at other sites. We speculate that our results may be attributable to an association between low serum albumin levels and physiological events associated with angiogenesis.

A software architecture for supporting the exchange of electronic manuscripts

As electronic-manuscript exchange becomes more prevalent, problems arise in translating among the wide variety of electronic representations. The optimum solution is a system that can support both the use and the creation of translation tools.

A case study: productivity and quality gains using an object-oriented framework

The Neuro-Oncology Information System (NOIS) supports researchers and other personnel throughout the United States engaged in brain tumor research. Graphical user interfaces that allow data input into the NOIS have been evolving over several years. This paper describes the design and implementation of the NOIS Input Forms as they migrated from a procedural approach to a static object-oriented approach, and finally to a framework approach in which not only static components were reused, but also the patterns of interaction among the components. The paper documents a significant gain in productivity and quality that was realized when using the framework design paradigm. Copyright

Estimating confidence intervals for simulations of computer systems

In simulation studies, means, percentiles, or pro portions are often used to summarize measurements of system performance. We describe procedures for estimating confidence intervals for each of these three statistics. We conclude that proportions are generally best suited to computer simulation studies. We present empirical data that clarifies the proce dures and justifies the recommendation of proportions.

Statistical Methods for Comparing Computer Services

The advent of remote terminal access to computer systems, especially as provided by computer networks, has created a marketplace in which computer services rather than computer systems are being sold. And along with that marketplace has come the need for a way to compare and evaluate computer services. This paper presents a methodology for designing and analyzing computer service comparison experiments with the objective of selecting the best system.

Software support for distributed resource sharing

Abstract The Desperanto Research project has been investigating the design and development of software to support distributed computing environments consisting of networks of autonomous, heterogeneous computer systems. The design goals which distinguish this project from other related efforts are (1) finding universally applicable solutions to problems (i.e. solutions which are not specific to one system or application domain), and (2) finding solutions which do not require changing existing software.

Automatic form generation

The Acuity project, in support of a collaborative brain‐tumor research effort, provides WWW‐based input forms implemented as Java applets for updating a WWW‐accessible database. The continuing need to develop new, but closely related, input forms motivated the design and implementation of the Acuity Form Generator (AFG), an automatic form‐generation tool. This paper documents the AFG technology. Copyright