Scalability support for multiparty multimedia communications

In this paper, we propose a new communication abstraction known as the group channel which facilitates and supports the implementation of multiparty interactive multimedia (MIM) applications such as video conferencing. The group channel is a high-level abstraction for group communication. The credit scheme and the dynamic bandwidth calibration scheme are provided as an integral part of the group channel service for allocating network bandwidth dynamically as participants join and leave the group channel. The multimedia transport protocol (MTP) is proposed as a realization of the group channel service in the ATM network. Its prototype implementation and a simple multiparty video-conferencing application built on top of the MTP prototype are described in this paper. Our results show that the group channel is capable of guaranteeing the performance of MIM applications irrespective of the group size and differences in workstation speeds.     

Using Personal Traces in Context Space: Towards Context Trace Technology

Wearables are often described with a focus on providing the user with wearable information access and communication means. The contextual information retrieval aspect is, however, an essential feature of such systems, as in, for example, the Remembrance Agent [1] where manually entered search-terms are used for presenting relevant situational information, or as in different location-based systems [2]. In this position paper we outline a general framework of contextually aware wearable systems, and suggest how such mechanisms, collecting massive traces of the user context, may lead to several other interesting uses in what we will call context trace technology.     

The Well Mannered Wearable Computer

In this paper we describe continuing work being carried out as part of the Bristol Wearable Computing Initiative. We are interested in the use of context sensors to improve the usefulness of wearable computers. A CyberJacket incorporating a Tourist Guide application has been built, and we have experimented with location and movement sensing devices to improve its performance. In particular, we have researched processing techniques for data from accelerometers which enable the wearable computer to determine the user’s activity. We have experimented with, and review, techniques already employed by others; and then propose new methods for analysing the data delivered by these devices. We try to minimise the number of devices needed, and use a single X-Y accelerometer device. Using our techniques we have adapted our CyberJacket and Tourist Guide to include a multimedia presentation which gives the user information using different media depending on the user’s activity as well as location.     

TRIP: A Low-Cost Vision-Based Location System for Ubiquitous Computing

Sentient Computing provides computers with perception so that they can react and provide assistance to user activities. Physical spaces are made sentient when they are wired with networks of sensors capturing context data, which is communicated to computing devices spread through the environment. These devices interpret the information provided and react by performing the actions expected by the user. Among the types of context information provided by sensors, location has proven to be especially useful. Since location is an important context that changes whenever the user moves, a reliable location-tracking system is critical to many sentient applications. However, the sensor technologies used in indoor location tracking are expensive and complex to deploy, configure and maintain. These factors have prevented a wider adoption of Sentient Computing in our living and working spaces. This paper presents TRIP, a low-cost and easily deployable vision-based sensor technology addressing these issues. TRIP employs off-the-shelf hardware (low-cost CCD cameras and PCs) and printable 2-D circular markers for entity identification and location. The usability of TRIP is illustrated through the implementation of several sentient applications.     

Location Models from the Perspective of Context-Aware Applications and Mobile Ad Hoc Networks

Location models are crucial for providing location-dependent data to context-aware applications. In this paper, we present two approaches for modeling location information taken from an infrastructure-based and an ad hoc network-based application scenario. From these approaches we derive requirements for a general location modeling language for ubiquitous computing. Correspondence to: M. Bauer, Fakult?t Informatik, Universit?t Stuttgart, Breitwiesenstr. 20-22, D-70565 Stuttgart, Germany. Email: mabauer@informatik.uni-stuttgart.de     

A tool for model-checking Markov chains

Markov chains are widely used in the context of the performance and reliability modeling of various systems. Model checking of such chains with respect to a given (branching) temporal logic formula has been proposed for both discrete [34, 10] and continuous time settings [7, 12]. In this paper, we describe a prototype model checker for discrete and continuous-time Markov chains, the Erlangen–Twente Markov Chain Checker E⊢MC², where properties are expressed in appropriate extensions of CTL. We illustrate the general benefits of this approach and discuss the structure of the tool. Furthermore, we report on successful applications of the tool to some examples, highlighting lessons learned during the development and application of E⊢MC². Published online: 19 November 2002 Correspondence to: Holger Hermanns     

Aware Community Portals: Shared Information Appliances for Transitional Spaces

People wish to maintain a level of awareness of timely information, including presence of others in the workplace and other social settings. We believe this provides better exchange, coordination and contact within a community, especially as people work in asynchronous times and distributed locations. The challenge is to develop lightweight techniques for awareness, interaction and communication using shared information appliances. In this paper, we describe the design of an exploratory responsive display projected within a shared workspace at the MIT Media Lab. The system uses visual sensing to provide relevant information and constructs traces of people’s activity over time. Such aware portals may be deployed in casual workplace domains, distributed workgroups, and everyday public spaces.     

Progressive evaluation of nested aggregate queries

In many decision-making scenarios, decision makers require rapid feedback to their queries, which typically involve aggregates. The traditional blocking execution model can no longer meet the demands of these users. One promising approach in the literature, called online aggregation, evaluates an aggregation query progressively as follows: as soon as certain data have been evaluated, approximate answers are produced with their respective running confidence intervals; as more data are examined, the answers and their corresponding running confidence intervals are refined. In this paper, we extend this approach to handle nested queries with aggregates (i.e., at least one inner query block is an aggregate query) by providing users with (approximate) answers progressively as the inner aggregation query blocks are evaluated. We address the new issues pose by nested queries. In particular, the answer space begins with a superset of the final answers and is refined as the aggregates from the inner query blocks are refined. For the intermediary answers to be meaningful, they have to be interpreted with the aggregates from the inner queries. We also propose a multi-threaded model in evaluating such queries: each query block is assigned to a thread, and the threads can be evaluated concurrently and independently. The time slice across the threads is nondeterministic in the sense that the user controls the relative rate at which these subqueries are being evaluated. For enumerative nested queries, we propose a priority-based evaluation strategy to present answers that are certainly in the final answer space first, before presenting those whose validity may be affected as the inner query aggregates are refined. We implemented a prototype system using Java and evaluated our system. Results for nested queries with a level and multiple levels of nesting are reported. Our results show the effectiveness of the proposed mechanisms in providing progressive feedback that reduces the initial waiting time of users significantly without sacrificing the quality of the answers. Received April 25, 2000 / Accepted June 27, 2000     

AudioGPS: Spatial Audio Navigation with a Minimal Attention Interface

In this paper we describe a prototype spatial audio user interface for a Global Positioning System (GPS). The interface is designed to allow mobile users to carry out location tasks while their eyes, hands or attention are otherwise engaged. Audio user interfaces for GPS have typically been designed to meet the needs of visually impaired users, and generally, though not exclusively, employ speech-audio. In contrast, our prototype system uses a simple form of non-speech, spatial audio. This paper analyses various candidate audio mappings for location and distance information. A variety of tasks, design considerations, design trade-offs and opportunities are considered. The findings from pilot empirical testing are reported. Finally, opportunities for improvements to the system and for future evaluation are explored.     

Content-based navigation of music using melodic pitch contours

We describe a system which supports dynamic user interaction with multimedia information using content-based hypermedia navigation techniques, specialising in a technique for navigation of musical content. The model combines the principles of open hypermedia, whereby hypermedia link information is maintained by a link service, with content-based retrieval techniques in which a database is queried based on a feature of the multimedia content; our approach could be described as ‘content-based retrieval of hypermedia links’. The experimental system focuses on temporal media and consists of a set of component-based navigational hypermedia tools. We propose the use of melodic pitch contours in this context and we present techniques for storing and querying contours, together with experimental results. Techniques for integrating the contour database with open hypermedia systems are also discussed.     

Infopipes: An abstraction for multimedia streaming

To simplify the task of building distributed streaming applications, we propose a new abstraction for information flow – Infopipes. Infopipes make information flow primary, not an auxiliary mechanism that is hidden away. Systems are built by connecting predefined component Infopipes such as sources, sinks, buffers, filters, broadcasting pipes, and multiplexing pipes. The goal of Infopipes is not to hide communication, like an RPC system, but to reify it: to represent communication explicitly as objects that the program can interrogate and manipulate. Moreover, these objects represent communication in application-level terms, not in terms of network or process implementation.     

A User-Centered Location Model

This paper discusses the user-centered location model used in comMotion. In this context, the location model refers to a set of learned places (destinations), which coincide to a latitude and a longitude, that the user has categorized. It also includes knowledge of the routes between the destinations and the time it takes to travel them. The model is based on user experience, i.e. his patterns of mobility, so no two models are the same. We also discuss the pattern recognition models implemented for route learning, route prediction and estimation of time to arrival. Correspondence to: Ms N. Marmasse, MIT Media Laboratory, 20 Ames Street, Cambridge, MA 02139, USA. Email: nmarmas@media.mit.edu     

Citywide: Supporting Interactive Digital Experiences Across Physical Space

The Citywide project is exploring ways in which technology can provide people with rich and engaging digital experiences as they move through physical space, including historical experiences, performances and games. This paper describes some initial results and experiences with this project based upon two prototype demonstrators. In the first, we describe an application in which a search party explores an archaeological site, uncovering enacted scenes within the virtual world that are of a historical relevance to their particular physical location. In the second, we describe a museum experience where participants explore an outdoors location, hunting for buried virtual artifacts that they then bring back to a museum for a more detailed study. Our demonstrators employ a varied set of devices, including mobile wireless interfaces for locating hotspots of virtual activity when outdoors, to give different experiences of the virtual world depending upon location, task, available equipment and accuracy of tracking. We conclude by discussing some of the potential advantages of using an underlying shared virtual world to support interactive experiences across extended physical settings.     

Expressing Location Information for Applications in the Internet

As part of the Spatial Location Protocol activity in the Internet Engineering Task Force (IETF), we have been working on how to express location information in an interoperable way in the Internet. The objective of this paper is to share our ideas on concepts for enabling interoperability and reuse of location information. These concepts can also be used in the area of ubiquitous computing. Correspondence to: Ms M. Korkea-aho, Department of Computer Science & Engineering, Helsinki University of Technology, Apollokatu 10 A 49, FIN-00100 Helsinki, Finland. Email: mari.korkea-aho@iki.fi     

Contextual Virtual Interaction as Part of Ubiquitous Game Design and Development

This paper relates to the problems of designing rich interaction, in the context of multi-player games, that would adequately support communication, control and co-ordination. The aspects of fun and rich experiences, usually required within the entertainment context, are easily overlooked in technologically driven system design. The concepts of a future ubiquitous game can be difficult to comprehend and evaluate in cases where a fully functioning physical prototype is not an option. One solution for the problem is Contextual Virtual Reality Prototyping that adds the missing context to the design simulations. The product can be designed and demonstrated in the corresponding environment, thus making it easier to understand the use-cases of, for example, a mobile device that has various location-dependent features. The main contribution of this research is the design and development approach that supports the creation of rich interaction. The primary emphasis of the approach is to avoid purely technologically driven design and development, but rather to provide a supporting, or even a guiding, approach that focuses on the creative process and conceptual understanding of rich interaction. This conceptually grounded content production-oriented approach to interactive system design is described and evaluated. Correspondence to: T. Manninen, Department of Information Processing Science, University of Oulu, PO Box 3000, 90014 Oulun Yliopisto, Finland. Email: tony.manninen@oulu.fi     

Beyond Position Awareness

Location models are merely based on positional information. Using wireless sensor networks, however, allows us to extract information which can be related to different levels of semantic proximity of different devices. Based on this observation, the paper proposes a semantic proximity hierarchy based on a wireless sensor network. In this paper, we argue that the proposed proximity hierarchy adds a new and complementary dimension to pure positional location information. The paper discusses the proposed hierarchy, gives application examples and some preliminary experimental results. Correspondence to: Mr S Antifakos, Perceptual Computing and Computer Vision Group, ETH Zentrum, CH08092 Zurich, Switzerland. Email: antifakos@inf.ethz.ch     

A hybrid system approach for supporting digital libraries

A digital library (DL) consists of a database which contains library information and a user interface which provides a visual window for users to search relevant information stored in the database. Thus, an abstract structure of a digital library can be defined as a combination of a special purpose database and a user-friendly interface. This paper addresses one of the fundamental aspects of such a combination. This is the formal data structure for linking an object oriented database with hypermedia to support digital libraries. It is important to establish a formal structure for a digital library in order to efficiently maintain different types of library information. This article discusses how to build an object oriented hybrid system to support digital libraries. In particular, we focus on the discussion of a general purpose data model for digital libraries and the design of the corresponding hypermedia interface. The significant features of this research are, first, a formalized data model to define a digital library system structure; second, a practical approach to manage the global schema of a library system; and finally, a design strategy to integrate hypermedia with databases to support a wide range of application areas. Received: 15 December 1997 / Revised: June 1999     

2PSM: an efficient framework for searching video information in a limited-bandwidth environment

We present a novel technique, called 2-Phase Service Model, for streaming videos to home users in a limited-bandwidth environment. This scheme first delivers some number of non-adjacent data fragments to the client in Phase 1. The missing fragments are then transmitted in Phase 2 as the client is playing back the video. This approach offers many benefits. The isochronous bandwidth required for Phase 2 can be controlled within the capability of the transport medium. The data fragments received during Phase 1 can be used to provide an excellent preview of the video. They can also be used to facilitate VCR-style operations such as fast-forward and fast-reverse. Systems designed based on this method are less expensive because the fast-forward and fast-reverse versions of the video files are no longer needed. Eliminating these files also improves system performance because mapping between the regular files and their fast-forward and fast-reverse versions is no longer part of the VCR operations. Furthermore, since each client machine handles its own VCR-style interaction, this technique is very scalable. We provide simulation results to show that 2-Phase Service Model is able to handle VCR functions efficiently. We also implement a video player called {\em FRVplayer}. With this prototype, we are able to judge that the visual quality of the previews and VCR-style operations is excellent. These features are essential to many important applications. We discuss the application of FRVplayer in the design of a video management system, called VideoCenter. This system is intended for Internet applications such as digital video libraries.     

Problem-Driven Approach to the Design of Information Technology Systems Supporting Complex Cognitive Tasks

The present paper proposes a methodological framework for the design and evaluation of information technology systems supporting complex cognitive tasks. The aim of the methodological framework is to permit the design of systems which: (1) address the cognitive difficulties met by potential users in performing complex problem-solving tasks; (2) improve their potential users’ problem-solving performance; and (3) achieve compatibility with potential users’ competences and working environment. After a short review of the weaknesses of existing systems supposed to support complex cognitive tasks, the theoretical foundations of the proposed methodology are presented. These are the ergonomic work analysis of French ergonomists, cognitive engineering, cognitive anthropology–ethnomethodology and activity theory. The third section of the paper describes the generic ergonomic model, which constitutes a frame of reference useful for the analyst of the work situation to which the information technology system is addressed. In the fourth section, the proposed methodology is outlined, and in the fifth a case study demonstrating an application of the methodology is summarised. In the epilogue, the differences between the proposed methodological framework and other more conventional approaches are discussed. Finally, directions for future developments of the problem-driven approach are proposed.     

Exploring Context-aware Information Push

Despite much interest over recent years in the area of context-aware computing, there are still a number of significant gaps in our understanding of the HCI issues associated with such systems. One particular issue that remains relatively unexplored is how to design around the apparently conflicting goals of adapting to changes in context while at the same time adhering to the principle of predictability. In this paper, we describe our exploration into this issue through two alternative designs of an interactive context-aware tourist guide. One original design was based around information pull, i.e. the emphasis is on the user to decide when context-aware information is presented. Our second design incorporates the notion of information push whereby the actual presentation of context-aware information is triggered by contextual events, e.g. changes in the user’s location or changes to the opening times of attractions. Through the evaluation of these alternative designs we hope to gain a better understanding of the usability implications relating to push vs. pull in both this specific domain and in interactive context-aware systems in general.