This paper presents visualization and layout schemes for a multi-person conversational setting.

Organizations, families, institutions evolve a shared culture and history. In this work, we describe a system to facilitate conversation and storytelling about this collective past. Users explore digital archives of shared materials such as photographs, video, and text documents on a tabletop interface. Both the software and the interface encourage natural conversation and reflection. This work is an application of our ongoing research on systems for multiple, co-present users to explore digital collections. In this paper, we present a case study of our own group history along with the software extensions developed for this scenario. These extensions include methods for easily branching off from and returning to previous threads of the exploration, incorporating background contexts that support a variety of view points and flexible story sharing, and supporting the active and passive discovery of relevant information.

In this paper, we present visualization and layout algorithms that can enhance informal storytelling using personal digital data such as photos in a face-to-face social setting. In order to build a more intuitive browser for retrieval, navigation and story-telling, we introduce a novel optimized layout technique for large image sets which respects (context sensitive) mutual similarities as visualized on a shared 2-D display (a table-top). The experimental results show a more perceptually intuitive and informative visualization of traditional CBIR-based retrievals, providing not only a better understanding of the query context but also aiding the user in forming new queries. A framework for user-modeling is also introduced and tested. This allows the system to adapt to the user's preferences and relevance feedback.

Desktop computers are not designed for multi-person face-to-face conversation in a social setting. We describe the design of a novel user interface for multi-user interactive informal storytelling. Our design is guided by principles of experience sharing, the disappearing computer, visual navigation, and implicit query formulation.

This paper presents a new scheduling scheme to support premium service in the Differentiated Service (DiffServ) architecture. It is based on weighted packet scheduling policies such as weighted round robin or fair queuing. The key feature of the new scheduling scheme is to change the scheduling weights of Behavior Aggregates adaptively. By adaptively adjusting the weights according to the dynamics of the average queue size of premium service, the proposed scheme can achieve low loss rate, low delay and delay jitter for the premium service. Moreover, it requires neither rigid admission control nor accurate traffic conditioning to support premium service in the DiffServ architecture. This adaptive packet scheduling is shown to absorb the transient burstiness of the Expedited Forwarding (EF) aggregate — which is caused by the traffic distortion inside the network —without incurring packet loss or increasing the queuing delay.

We present CReMeS, a CORBA-compliant design and implementation of a new real-time communication service. It provides for efficient, predictable, and scalable communication between information producers and consumers. The CReMeS architecture is based on MidART’s Real-Time Channel-based Reflective Memory (RT-CRM) abstraction. This architecture supports the separation of QoS specification between producer and consumer of data and employs a userlevel scheduling scheme for communicating real-time tasks. These help us achieve end-to-end predictability and allows our service to scale. The CReMeS architecture provides a CORBA interface to applications and demands no changes to the ORB layer and the language mapping layer. Thus, it can run on non real-time Off-The-Shelf ORBs and enables applications on these ORBs to have scalable and end-to-end predictable asynchronous communication facility. In addition, an application designer can select whether to use an out-of-band channel or the ORB GIOP/IIOP for data communication. This permits a trade-off between performance, predictability and reliability. Experimental results demonstrate that our architecture can achieve better performance and predictability than a real-time implementation of the CORBA Event Service when the out-of-band channel is employed for data communication; it delivers better predictability with comparable performance when the ORB GIOP/IIOP is used.

In this paper, we propose and present Real-Time Channel-based Reflective Memory (RT-CRM) – a new programming model and middleware communication service for constructing distributed real-time applications on commercially available open systems. RT-CRM provides remote realtime data reflection abstraction using a simple writer-push model. This writer-push approach enables us to easily decouple the QoS characteristics of the writers from that of the readers. This decoupling is crucial in supporting different kinds of remote data transfer and access needs that one often finds in distributed real-time systems. We will describe the design of RT-CRM, along with a set of easy-to-use API to access the RT-CRM service. We have implemented RT-CRM as part of a larger real-time middleware project, MidART.We address many of the important implementation issues including buffer management and QoS support. We demonstrate the feasibility of RT-CRM through a discussion of our application programming support and performance data.

Unique challenges are present when one tries to build distributed real-time applications using standard o-the-shelf systems which are in common use but are not necessarily designed specifically for real-time systems. In particular, to realize end-to-end predictability when, say, a process on one node sends data to a process on another node, several issues must be addressed: (1) mapping application real-time requirements into requirements imposed on the system schedulable entities (tasks), (2) ensuring predictable execution of the tasks in the face of possible priority inversions, limited OS level real-time scheduling support, and limited number of priorities, and (3) integrating real-time and non-real-time tasks in the same platform. In this paper, we propose solutions to these challenges. In particular, we present user-level scheduling schemes for communicating tasks. These solutions are practical and are based on simple primitives that can be found in most of today's commonly used operating systems. To validate our design and to examine the feasibility of user-level scheduling in actual systems, we have implemented our solutions in MidART running on PCs with Windows NT operating system over UDP/IP and Fast Ethernet LANs. This paper contributes to further our understanding of how to build real-time systems using commercially available o-the-shelf components.

Medical advances make it increasingly possible for children with previously fatal illness to live and thrive. However, a significant number still experience repeated operations, hospitalizations, and invasive procedures, or need special care at home. Many do so with little or no intervention to help them and their families cope with the emotional stresses involved. One significant source of emotional and cognitive support is the community of patients and families who have experienced similar medical procedures. However, in spite of a general willingness to share experiences, communication among patients and families is usually limited. To facilitate this process, we are investigating the use of computer technology to record, organize, and display stories about the experiences of families with children who have been treated for cardiac and neurological illness at Children’s Hospital, Boston. We are asking children and their families to record text and multimedia vignettes describing some aspect of their illness, coping strategies, or care that might be useful to others. These contributions will be available for browsing at a secure World-Wide-Web site. However, economic realities preclude reliance on a professional site administrator to organize and monitor what we hope to be a rapidly growing Web site with a large, distributed authorship. The need to make the Web site fully accessible to users who have varying familiarity with computers and Web browsing imposes further constraints. We are therefore developing software to automate the process of managing and organizing an easily accessed Web site that contains an “Experience Journal.” We describe this software, the rationale for its development, and our plans for its use in the coming year.

Windows NT was not designed as a real-time operating system, but market forces and the acceptance of NT in industrial applications have generated a need for achieving real-time functionality with NT. As its use for real-time applications proliferates, based on an experimental evaluation of NT, we quantitatively characterize the obstacles placed by NT. As a result of these observations, we provide a set of recommendations for users to consider while building real-time applications on NT. These are validated by the use of NT for a prototype application involving real-time control that includes multimedia information processing. The results of the above study should provide system designers with guidelines, as well as insight, into the design of an architecture based on NT for supporting applications with components having real-time constraints.

This paper describes our current work on scheduling communicating real-time tasks in a distributed environment. Unique challenges are presented when one tries to build distributed realtime applications using standard off-the-shelf systems which are in common use but are not necessarily designed for real-time systems. In particular, one must deal with (1) mapping application real-time requirements into system schedulable entities, (2) end-to-end scheduling in the face of possible priority inversion, (3) limited real-time scheduling support and limited number of priorities, and (4) integrating real-time and non-real-time tasks in the same platform. Due to space limitations, this paper focuses on solving the first two challenges. The complete solution will be presented in a forthcoming paper. We have implemented these solutions in our network middleware MidART running on PCs with Windows NT operating system over Ethernet LANs.

In this paper, we describe our experience in the implementation of MidART – Middleware and network Architecture for distributed Real-Time systems. Our MidART project addresses the problem of middleware design to support high speed network based distributed real-time applications. The uniqueness of MidART lies in the simplicity of services provided and the flexibility of data reflection models, compared with more general purpose but much more complicated middleware such as CORBA implementations. This simplicity leads to ease of understanding and ease of use by application builders, while its flexibility sufficiently serves the needs of the class of real-time applications MidART is designed for.

In this paper, we propose and present Real-Time Channel-based Reflective Memory (RT-CRM) – a useful programming model and middleware communication service for constructing distributed real-time industrial monitoring and control applications on commercially available open systems. RT-CRM provides remote real-time data reflection abstraction using a simple writer-push model. This writer-push approach enables us to easily decouple the QoS characteristics of the writers from that of the readers. This decoupling is crucial in supporting different kinds of remote data transfer and access needs that one often finds in distributed industrial systems. We will describe the design of RT-CRM, along with a set of easy-to-use API to access the RT-CRM service. We have implemented RT-CRM as part of a larger real-time middleware project, MidART. We address many of the important implementation issues including buffer management and QoS support. We demonstrate the feasiblity of RT-CRM through a discussion of our application programming support and preliminary performance data.

We present an adaptive network layer protocol for VBR video transport. It: (1) minimizes the buffer requirement in the network while guaranteeing that packets of VBR encoded video flows will not be lost, and (2) minimizes the end-to-end delay and jitter of frames. To achieve the former objective, we utilize a receiver-oriented adaptive credit-based flow control algorithm, and derive the necessary and sufficient number of buffers that should be reserved for ensuring its reliability. To minimize the end-to-end delay and jitter for VBR encoded video streams, we: (1) present bandwidth estimation techniques which exploit the structure of the video traffic, and (2) define a new fairness criteria for buffer allocation and then present a fair buffer/bandwidth allocation algorithm. We experimentally evaluate this protocol for a wide range of parameters and many network configurations, and demonstrate its adaptability. We also compare the performance of the protocol with numerous other schemes and demonstrate its suitability for video transport.

In this paper we address the problem of middleware design for constructing ATM LAN based distributed industrial plant monitoring and control systems. In particular, we present a real-time client-server programming model based on a uniform ATM network. This model is being realized in our middleware called MidART. The middleware provides a set of industrial application specic but network transparent programming abstractions and application programming interface (API) that support individual application QoS requirements. In order to achieve on-demand transmission of plant data, we have developed a concept called selective real-time channels to be supported by MidART. We present the design and protocols of selective real-time channels and describe how QoS requirements of applications are guaranteed.

This is a position paper discussing the requirements of networks in industrial environments, especially with respect to digital audio and video. Topics include resource allocation, issues surrounding switching, scheduling, and priorities, end system interface requirements, and traffic characteristics and their implications on flow control.

Building multi-user interactive multimedia environments at Mitsubishi Electric Research Laboratories (MERL) is a highly interdisciplinary activity, which involves the efforts of more than a dozen members of the laboratory. This report describes this research at three levels. At the bottom, supporting everything, are high-speed networks. On top of networks, we have built a piece of middleware called Spline. Finally, Diamond Park is an experimental environment we are building using Spline.

Most real-time scheduling algorithms schedule tasks with regard to their worst case computation times. Resources reclaiming refers to the problem of utilizing the resources left unused by a task when it executes in less than its worst case computation time, or when a task is deleted from the current schedule. Dynamic resource reclaiming algorithms that are effective, avoid any run time anomalies, and have bounded overhead costs that are independent of the number of tasks in the schedule are presented. Each task is assumed to have a worst case computation time, a deadline, and a set of resource requirements. The algorithms utilize the information given in a multiprocessor task schedule and perform online local optimization. The effectiveness of the algorithms is demonstrated through simulation studies.