Mobile devices such as smartphones have a number of sensors that can be exploited to solve a number of problems related to health care delivery. In this paper we use accelerometer, gyroscope, and compass sensors on smart-phones to solve a location tracking problem common to many emergency departments. An emergency department typically has unique characteristics including not being friendly to be visually surveyed, since the layout consists of many isolated islands and the workstation layout is not standardized. The spaghetti diagram is a tool to help to identify areas where time can be saved by visualizing unnecessary movement of products, staff or patients. We report the development of an automated tool to create spaghetti diagrams of movements of personnel in a non-intrusive way. A preliminary prototype to produce paths showed very encouraging results. We also identify challenges and our approach to meet them.

One of the government missions identified by the federal enterprise architecture is to use computer and networking technologies to develop infrastructure to support information sharing within government organizations as well as with external stakeholders. Currently, considerable information is being maintained at individual organizations in the form of large repositories/digital libraries with no efficient means of sharing it with other government organizations and with other external user communities, including the general public. A major obstacle to information sharing is the lack of a framework and an infrastructure that allows government organizations to share information selectively with different user groups. Lack of such a framework creates unwillingness among government organizations to share their digital content. A mechanism needs to be in place where policy makers can specify which documents can be moved from one organization to another organization and/or who can access these transferred documents. Furthermore, a system is needed that enforces these policies in realtime when external events dictate a change of policies. In this paper, we propose a framework for specification, management and enforcement of dynamic access policies across multiple geographically distributed organizations. The framework can be instantiated to integrate with individual digital library systems and provide the necessary infrastructure to provide policy controlled access control management

In this paper, we propose a P2P digital library that takes advantage of P2P networks and digital libraries. The key problem with P2P network searches is the low recall value, time to completion and its high use of network bandwidth. In this paper we introduce Freelib a universal client that once installed on a user's machine will connect itself to a P2P network and after a few searches will become aware of the community the user belongs to. The architecture of Freelib is such that a Web of connections is created automatically for people who share common interests, i.e., have similar searches. We report in this paper on the first prototype client the design changes made in the architecture as we actually built the client and the development of an emulator that can validate the working of the client in a real P2P network.

Abstract The paper describes a media access system for satellite network uplinks. The media access protocol is designed to support a range of low‐level protocols using a dual‐framing system, that is, there is a synchronous traffic subframe in which registered station requests are assigned fixed blocks or slots and an asynchronous traffic subframe for unregistered station random access on a contention basis. Slots for the registered stations are assigned through request to the satellite; the remaining frame time is assigned to unregistered stations. Capacity waste through contention resulting in collisions is minimized. The system uses dynamic bandwidth (bit rate) allocation for each channel, that is, the base frequency and bandwidth are changed for each channel at frame boundaries. The total bandwidth for the sum of all uplink channels is fixed. Channels that have low load based upon their request in a prior uplink frame are assigned lower bandwidth, while those with higher loading are provided larger bandwidth. By sharing bandwidth over channels at frame boundaries, overall network efficiency and fairness are significantly enhanced. Bandwidth allocation is decided in the satellite. It allocates sufficient bandwidth for all synchronous traffic and then commits the remaining bandwidth to asynchronous traffic. Here, the allocation for asynchronous traffic provides each channel with sufficient slots so that equal probability of success for stations sharing the channel can be expected. The combination of traffic assignment and bandwidth allocation provides significant improvement in overall network efficiency and fairness for all traffic types. The hardware implementation of media access for variable bandwidth sharing between channels use the concepts of Digital Software Radio. Copyright © 2003 John Wiley & Sons, Ltd.

At Old Dominion University, we have designed and implemented a Java-based distance education system, which we term IRI-h (for Interactive Remote Instruction-heterogeneous). IRI-h is designed to function on a number of heterogeneous platforms, and within heterogeneous network environments. IRI-h builds on the success of its predecessor system IRI, but attempts to avoid a number of identified pitfalls and deficiencies such as platform dependence, poor scalability, and the need for a homogeneous controlled network environment. We present the design and software architecture of IRI-h which continues to offer audio, video, and tool sharing services within a synchronous virtual classroom environment, albeit in a platform independent manner. Furthermore, the proposed architecture accommodates class participants with no multicast capabilities, or limited connectivity bandwidth by offering tunneling, and rate adaptation services.

We used our Original Interactive Remote Instruction (IRI) system to teach scores of university classes over the past years at sites up to 300 km apart. While this system is a prototype, its use in real classes allows us to deal with crucial issues in distributed education instruction systems. We describe our motivation and vision for a reimplementation of IRI that supports synchronous and asynchronous distance education. This new version, called IRI-h (h for hetergeneous), is coded in Java and executes on several different platforms. IRI-h extends IRI both to multiple platforms and heterogeneous network experiences with the developing prototype, including preliminary performance evaluation, and also unresolved issues still to be addressed.

With the increasing complexity of large scale distributed (LSD) systems, an efficient monitoring mechanism has become an essential service for improving the performance and reliability of such complex applications. The paper presents a scalable, dynamic, flexible and nonintrusive monitoring architecture for managing large scale distributed (LSD) systems. This architecture, which is referred to as the HiFi monitoring system, detects and classifies interesting primitive and composite events and performs either a corrective or steering action. When appropriate, information is also disseminated to management applications, such as reactive control tools. The outlined solution offers improvements over related works by supporting new monitoring techniques such as hierarchical filtering based monitoring and filter incarnation that improve the monitoring scalability and dynamism which are required for managing large scale distributed systems. The HiFi monitoring system has been implemented and used at the Old Dominion University for monitoring and steering Interactive Remote Instruction (IRI) which is a large scale distributed multimedia system for distance learning.

Obtaining feedback information regarding the state of receivers in a multicast session is a fundamental problem that often arises in collaborative multimedia systems. In this paper we present a generalized abstraction of the state feedback problem. Then, we present a feedback protocol that addresses some of the special cases that commonly arise. The presented feedback protocol is suitable for application in best-effort unreliable networks such as the Internet. It allows for obtaining the desired state feedback about a group of receivers, where each receiver may be in one of a set of finite states. The efficiency of the proposed protocol in eliminating the reply implosion problem is illustrated by simulation experiments.

Collaborative multimedia systems demand overall session quality control beyond the level of quality of service (QoS) pertaining to individual streams in isolation of others. To this end, the authors have recently introduced the concept of quality of session (QoSess) control. At every instant in time, the quality of the session depends on the actual QoS offered by the system to each of the application streams, as well as on the relative priorities of these streams according to the application semantics. The authors present a framework for achieving QoSess control, and describe the architecture of a distributed QoSess control layer. In addition, they describe a new inter-stream bandwidth adaptation mechanism, which is used by the QoSess control layer to dynamically control the bandwidth shares of the streams belonging to a session.

Controlling the quality of collaborative multimedia sessions, that deploy multiple media streams, is a challenging problem. In this paper we present a framework for achieving quality of session (QoSess) control focusing on two main components of the QoSess control layer. The first component is a scalable and robust feedback mechanism which allows for determining the worst case state among a group of receivers of a stream. This mechanism is used for controlling the transmission rate of multimedia sources in the cases of layered and single-rate streams. The second component is the inter-stream bandwidth adaptation mechanism that dynamically controls the bandwidth shares of the streams belonging to a session. We compare the performance of several adaptation algorithms. Additionally, in order to ensure stability and responsiveness in the inter-stream adaptation process, several measures are taken, including devising a domain rate control protocol. The performance of our mechanisms is analyzed and their advantages are demonstrated by simulation and experimental results.

Collaborative multimedia systems encompass many Internet applications such as desktop conferencing and interactive distance learning. These applications often contain resources, such as audio, video and shared applications, that must be accessed exclusively by one participant at a time. We present a distributed algorithm that manages the access to these exclusive resources. The algorithm is based on the assumption that the transport layer provides reliable multicasting. Resources are classified into two main classes: primitive and composite. Composite resources consist of a set of two or more primitive resources. A token is associated with each resource unit, and a participant must obtain the resource's token before using the resource. To use a resource, certain permissions may be needed from certain entities such as the session coordinator, the current resource holder and, in some cases, the resource itself. The algorithm guarantees that at any given time, the resource is held by exactly one participant and the token of any resource will never be lost under all possible failure conditions.

Reliable multicast protocols are becoming an essential element in distributed applications such as interactive distance learning applications. However, the existing implementations of reliable multicast protocols are not sufficient to satisfy the group communications requirements of some distributed applications. Our experience of using number of multicast protocols in IRI distance learning applications shows the necessity of providing an application-layer reliable multicast server (RMS) to extend the primitive group communication services provided by such multicast protocols. Examples of such services include handling heterogeneous environments (such as LAN vs. WAN networks and different reliable multicast protocols), automatic fault recovery and simple application interface. In this paper, we motivate and describe the design and the implementation of RMS architecture which has been used in IRI learning sessions for two semesters. We also show how RMS improves the reliability, performance and flexibility of IRI sessions via supporting extended group communication services.

In new collaborative multimedia applications, there is a need for overall control, beyond the level of quality of service (QoS) as pertaining to individual streams in isolation of others. At every instant in time, the quality of the session, as perceived by the end user, depends on the priorities of the on-going streams, according to the application semantics, as well as on the actual QoS offered by the system to each of these streams. We introduce the concept of "Quality of Session" control. This is achieved by employing a monitoring mechanism for measuring the perceived QoS of each stream. In addition, in order to react to existing or potential bottlenecks in the network or end-systems, or skewness in the synchronization of views, an inter-stream adaptation mechanism is applied.

Parallel and distributed computing on a cluster of workstations is being increasingly applied to a variety of large size computational problems. Several software systems have been developed that make distributed computing available to an application programmer. However, these systems either are not Web-based or lack a collaborative environment. The increasing use of Web technology for Internet and Intranet applications is making the Web an attractive framework for solving distributed applications, in particular, because the interface can be made platform-independent. In this paper we describe JAVADC, a Web–Java-based framework for the execution of parallel SPMD applications which use PVM, pPVM and MPI. We also discuss the design of a collaborative, distributed computing environment, Arcade, focused on more general programming paradigms for multidisciplinary applications. Arcade is a Web-based integrated environment which provides support in all phases of the development of general multidisciplinary applications including the design, execution, monitoring and control of such applications. © 1997 John Wiley & Sons, Ltd.

We propose a quality of service (QoS) architecture, QUANTA, for an end system protocol suite. We use TCP(UDP)/IP over ATM as a testbed to develop the architecture. We measure the application level QoS in terms of throughput, delay, round trip time, and loss to identify the base line performance an application can expect from such an environment. From the no-load condition we measure the behavior of these protocols at various data rates and user submitted data block sizes. We demonstrate the tradeoffs involved in obtaining high throughput, low delays, low round trip time, and zero losses at different data rates. We use host load condition experiments to understand the interaction between the CPU intensive jobs and the communication intensive jobs. We use network load condition experiments to observe interaction between multiple streams of the above two protocol suites, and its effect on the application QoS. Given these observations we define the missing components in the current protocol architectures to provide tighter control on the QoS guarantees. Components we define in QUANTA include a two level application to network QoS translator protocol tuning components, local feedback component, class based scheduling etc.

Today a plethora of multimedia, hyperlink software and hardware components are available, as well as teleconferencing systems supporting collaborative work. However, few systems are easy for people to use for real applications such as support of remote instruction. Most importantly, none of these tools scale to use by more than a few users simultaneously. We describe our vision for a system which will support interactive remote instruction (IRI) to support college-level education across spatial boundaries in a manner largely transparent to students and faculty. We have implemented a prototype of this system which has been used to evaluate both the user-interface design and performance requirements. The goal is to have a user interface which models most of the interactions which occurs in a regular classroom. A key focus in this paper is the assessment of system requirements necessary to support large classes. That means that multimedia tools must support O(10), rather than O(1), simultaneous users and user-system interaction protocols must be effective and accepted by students and faculty with diverse backgrounds and computer sophistication.

The Distributed Queue Dual Bus (DQDB) system consists of a linear arrangement of N nodes that communicate with each other using two contra-flowing buses. The nodes use an extremely simple protocol to send messages on these buses. This simple, but elegant, system has been found to be very challenging to analyze. We consider a simple and uniform abstraction of this model to highlight the fairness issues in terms of average waiting time. We introduce a new approximation method to analyze the performance of DQDB system in terms of the average waiting time of a node expressed as a function of its position. Our approach abstracts the intimate relationship between the load of the system and its fairness characteristics, and explains all basic behavior profiles of DQDB observed in previous simulation. For the uniform DQDB with equal distance between adjacent nodes, we show that the system operates under three basic behavior profiles and a finite number of their combinations that depend on the load of the network. Consequently, the system is not fair at any load in terms of the average waiting times. We also show that the main theme of the analysis carries over to the general (nonuniform) DQDB. By suitably choosing the inter-node distances, the DQDB can be made fair around some loads, but such system will become unfair as the load changes. In the vicinity of a critical load, the uniform network runs into a state of instability, where its behavior fluctuates from one extreme to the other with small load variations. Our analysis is supported by simulation results.>

Execution time of an application running on a cluster of workstations is critically dependent upon the performance of the underlying communication network, especially when the application demands for large data transfers among workstations. In this research, we use parallel network approach to improve the communication network performance and demonstrate this in a real cluster computing environment using multiple Ethernets. We modified the PVM environment to pPVM to schedule the application data onto multiple networks, the scheduling strategy being either round-robin or adaptive. The adaptive strategy performs well for both equal and unequal distribution of background load on the channels, and also for time-varying background load.

Considers a simple and uniform abstraction of the distributed queue dual bus (DQDB) system of N nodes to highlight the fairness issues in terms of average waiting time. For the uniform DQDB with equal distance between adjacent nodes, the authors show that the system operates under three basic behavior profiles and a finite number of their combinations that depend on the load of the network. Consequently, the system is not fair at any load in terms of the average waiting times. In the vicinity of a critical load of 1-4/N the uniform network runs into a state akin to chaos, where its behavior fluctuates from one extreme to the other with a load variation of 2/N. The analysis is supported by simulation results. The authors also show that the main theme of the analysis carries over to the general (non-uniform) DQDB.>

Four factors in parallel token ring systems which can improve network performance are identified. An analytical model is developed to predict the performance of these systems. The predictions obtained with the analytical model are compared with simulation results. While the current model accurately predicts the performance of networks with 16 or more rings, it is not so accurate at lower numbers of rings. The short/long cycle behavior of the token interarrival times is identified as one cause of the inaccuracies. The benefits and limitations of parallel token ring networks for gigabit speeds are discussed.>

A process model for software maintenance using the decision-based software development (DBSD) paradigm is described. The DBSD paradigm models the process of software development and maintenance as a continuous problem-solving activity where the decision is the focal point. An important aspect of this process is the preparation for perfective and corrective maintenance by identifying conditional decisions whose validation depends on experience with the production system. Validation requires the instrumentation of the production system to collect data which will support or refute the decision. The authors discuss the instrumenting of a prototype DBSD support environment to collect data to validate the proposed process model. Also given are the results of some preliminary data.>

The paper describes the operation and performance of an integrated traffic network using separate media access protocols to support different traffic types on a single unidirectional ring or bus. One protocol, based upon local carrier sensing (CSMA/RN) provides access for asynchronous traffic; the other, a 'train like' protocol called the circulating reservations packets (CRPs), provides access for synchronous voice and video traffic. Other media access protocols like slotted ring or QPSX are equally applicable for use as the asynchronous protocol.>

Abstract Current software development paradigms focus on the products of the development process. Much of the decision‐making process which produces these products is outside the scope of these paradigms. The decision‐based software development (DBSD) paradigm views the design process as a series of interrelated decisions which involve the identification and articulation of problems, alternatives, solutions and justifications. Decisions made by programmers and analysts are recorded in a project database. Unresolved problems are also recorded and resources for their resolution are allocated by management according to the overall development strategy. This decision structure is linked to the products affected by the relevant decisions and provides a process‐oriented view of the resulting system. Software maintenance uses this decision view of the system to understand the rationale behind the decisions affecting the part of the system to be modified. The relationships between decisions help assess the impact of changing one or more decisions. We describe D‐HyperCase, a prototype Decision‐Based Hypermedia System and give results of applying the DBSD approach during its development.

The decision-based software development (DBSD) paradigm is being developed to support the process of developing and maintaining software systems. The DBSD paradigm views the design process as a series of interrelated decisions which involve the identification and articulation of problems, alternatives, solutions, and justifications. Decisions made by programmers and analysts are recorded in a project database. Unresolved problems are also recorded, and resources for their resolution are allocated by management according to the overall development strategy. This decision structure is linked to the products affected by the relevant decisions and provides a process-oriented view of the resulting system. Software maintenance uses this decision view of the system to understand the rationale behind the decisions affecting the part of the system to be modified. The relationships between decisions help assess the impact of changing one or more decisions. The authors describe D-HyperCase, a prototype decision-based hypermedia system and give results of applying the DBSD approach during its development.>

A software maintenance task comprises the activities of understanding, assessment, analysis, realization and verification of the required changes. A decision-based software development methodology in which the various software objects are related by the decisions in which they are involved, is proposed. A decision relates a problem to its solution, gives alternate solutions which were considered and justifies the particular solution chosen. A decision or related set of decisions, provides a view of the software system relevant to that decision and allows the retrieval of source code which resulted from that decision. The design of D-HyperCase, a prototype decision-based software development support system, is described. Since this system is being developed using the decision-based approach, development experiences are discussed.>

Recently protocols have been introduced that enable the integration of synchronous traffic (voice or video) and asynchronous traffic (data) and extend the size of local area networks without loss in speed or capacity. One of these is DRAMA, a multiband protocol based on broadband technology. It provides dynamic allocation of bandwidth among clusters of nodes in the total network. In this paper, we propose and evaluate a number of traffic placement policies for such networks. Metrics used for performance evaluation include average network access delay, degree of fairness of access among the nodes, and network throughput. The feasibility of the DRAMA protocol is established through simulation studies. DRAMA provides effective integration of synchronous and asynchronous traffic due to its ability to separate traffic types. Under the suggested traffic placement policies, the DRAMA protocol is shown to handle diverse loads, mixes of traffic types, and numbers of nodes, as well as modifications to the network structure and momentary traffic overloads.

A file system tailored to the general needs of the office environment is proposed. This system supports large numbers of a wide variety of documents and inexact fuzzy queries on the documents. The file system is based on a multilevel file structure that combines and extends multikey extendible hashing and signature files to create a document-retrieval system that is more time efficient than other previously proposed systems and is also space efficient.>

The authors have designed a software maintenance support environment (SMSE) to assist in the maintenance of existing source code. They model software maintenance as a hybrid distributed problem-solving activity, in which the application-dependent knowledge is provided by the system, and common sense, programming expertise, and problem-solving knowledge are provided by the people on the project team. To define a set of requirements to be satisfied by a SMSE, a series of maintenance tasks were performed on an inventory control application consisting of about 68000 lines of Cobol program. These results of experiments, including lessons learned and requirements for an SMSE, are presented. A key role of the SMSE is to help the software engineer find all information relevant to a particular maintenance task without examining a lot of extraneous material. Access to the decision structure and the ability to assess the impact of decisions constitute the most important issue to be addressed by the SMSE. The experiments indicate that a high degree of reusability could be achieved for certain tasks using the information contained in the closure of that task.>

Recently protocols have been introduced which enable us to integrate periodic traffic (voice or video) and aperiodic traffic (data) and to extend the size of local area networks without any loss in speed and capacity. One of these, the DRAMA protocol, is based on broadband technology and allows for dynamic allocation of bandwidth to clusters of nodes in the total network. In this paper we propose a distributed algorithm to allocate bandwidth in a fair manner, where we have defined fair to mean that every node in the network, regardless of its location, should have the same expected access delay to the net. We show by means of simulation that the algorithm is stable and within a few percentage points of the optimal solution. Stability is measured in terms of the time it takes the system to return to near optimal distribution of the bandwidth after strong disturbances. The algorithm is shown to handle total reallocation of the resources within O(100ms).

A file system tailored to the general needs of the office environment is proposed. This system supports large numbers of a wide variety of documents and inexact ‘fuzzy’ queries on the documents. The file system is based on a multilevel file structure; the structure combines and extends multikey extendible hashing and signature files to create a document retrieval system that is more time efficient than other previously proposed systems, and also space efficient.

A new, fully-distributed protocol for integrated voice/data traffic in a local-area, random-access broadcast network is described. The protocol introduces a movable voice-data boundary to framed TDMA/CSMA and eliminates the requirement of system-wide synchronized clocks. The movable boundary is a major advantage in any system where fluctuations in voice and data loads are expected because assignment of idle capacity from one traffic class to the other increases the utilization of the channel. The protocol provides collision-free virtual circuits for voice and periods of non-persistent CSMA/CD for data traffic and call establishment, and can support multi-party calls as well as two-way conversations. The protocol allows variable-size voice packets that have very low overhead and variable-size data packets that may be much longer than voice packets. This is of significant practical advantage over previous work, which has required fixed-size voice and/or data packets, or voice packets with high overhead. A method of dynamically controlling the movable boundary to balance the voice and data traffic is also proposed.

As a result of the development of microcomputers, the term distributed computing has taken on new meaning. In this paper, we intend it to mean a general purpose computing system whose basic elements are microprocessors, and we are primarily concerned with the development of algorithms and the subsequent specification of software for the systems. We establish first a model for such a parallel asynchronous computing system giving particular attention to communications between microprocessors. Next, we propose a language for programs to execute on this system. Its syntax closely follows Simula, but its semantics are geared to the underlying hardware. The semantics we propose are such that we can use the programs both to investigate performance by simulation and to expound general techniques for algorithm construction for distributed systems.

We feel that for a long time introductory computer science courses have degenerated into courses more appropriately titled “Introduction to the Programming Language X” where X has historically been FORTRAN or BASIC and more recently PL/I or APL. In this paper we propose an introductory course which first, and foremost, teaches problem-solving methodology with the final stage of it being translation of an algorithm into a well-structured program. And, second, it achieves this in conjunction with an introduction to the major areas of computer science.