Ambient i,ledia for Peripherat Information Disptau

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1 Ambient i,ledia for Peripherat Information Disptau Hans-W. Gellersen, Albrecht Schmidt and Michael Beigl Telecooperation Office, University of KarIsruhe, Karlsruhe, Germany Abstract: In our everyday lives, we use surrounding living and working environments to arrange physical information artefacts such as books, pictures and calendars. However, when it comes to consumption of computer-based information, this is almost entirely based on attending to screens that separate us from our surroundings. In this paper, we explore the augmentative use of non-computer artefacts in our surroundings for peripheral display of digital information. We discuss system integration of such ambient media, the mapping of information to ambient media, and issues of flexibility and user control. Ambient media have been in everyday use in our work environment, and we report observations from which we conclude their utility as extensions to our digital information spaces. Keywords: Ambient media; Augmented reality; Calm technology; Linking virtual and physical worlds; Peripheral awareness; Ubiquitous computing 1. Introduction Our living and working environments constitute rich information spaces in which we arrange physical information objects - for instance tags, notes, books, files, photos, calendars - according to our needs. However, more and more of the information that we deal with is now digital, to take advantage of the versatility of computers and global networks. As a consequence, our interactions with information are increasingly based on keyboard, rnouse and monitor, not utilising the affordances inherent in our surrounding environments. New developments in computing address this issue, and promote the concept of interfacing digital information ("the virtual world") through our everyday environments ("the real world"). One of these developments is ubiquitous computing, based on small networked computing devices embedded everywhere in our physical environment. In the vision of ubiquitous computing, computers will become a calm technology at the periphery of our attention, and user interfaces will be replaced by "places to get things done" [1,2]. Another development toward interaction with digital information in the real world is augmented reality. Research in this area is concerned with computational augmentation of our perception and interaction in our physical environment. This includes work on subtle augmentation of environments similar to ubiquitous computing ideas, as well as work on situating virtual realities in the context of local environments [3]. A more specific aspect of interfacing digital information through physical environments is the use of our surroundings for information display. The rooms and buildings we live and work in contain rich resources for the display of information, in particular, for subtle displays at the periphery of our attention. For example, information may be displayed in changes in the lighting or in the ventilation, in which case lamps and fans are used as ambient media. There have been a range of examples of ambient media, for instance in arts installations, and their more general use for the expression of digital information has been investigated in the ambientroom project. The ambientroom is an experimental office space equipped with a range of ambient displays, for instance light patches on the wall, natural soundscapes in the background, and water ripples projected on the ceiling, to extend humancomputer-interaction beyond computer screens [4]. The ambientroom and other demonstrations of ambient media indicate their suitability to support peripheral awareness of information and, as such, to augment traditional human-computer interaction. However, if we assume general usability of the concept, fundamental questions arise, including: How can we integrate ambient media with digital information spaces in more general ways than used in the existing one-of-a-kind demonstrators? How can we approach design of ambient media spaces and map digital information to ambient media suited for their display? And how can we give people flexibility in use of ambient media in their personal information spaces? Springer-Verlag London Ltd Personal Technologies (1999) 3:

2 r 200 In this paper, we report on research into ambient media that is concerned with these questions. After a brief discussion of work related to our research, we will first discuss integration of ambient media in information spaces. We present design and implementation of the ambient media system, an open architecture for integration of ambient media with web-based information, based on standard WWW protocols for ease of deployment. Based on this system, we have integrated a variety of ambient media in our everyday work environment for further investigation. The second issue we address is the design problem of mapping digital information to ambient media. In this context we introduce the concept of ambient counterparts, which is based on the assumption that much of the information we handle in our digital worlds has a natural counterpart in our physical environment to which it can be related intuitively. We argue that identification of such counterparts will help to design ambient media that support visions of smoother transition between the digital world and the real world, and we demonstrate the concept with an application for web awareness. An interesting aspect of the application is the use of ambient counterparts for subtle comparison of different digital information sources. As a third issue, we discuss issues of user control and flexible use of ambient media. Our argument is that people often have changing information needs over time, and that they should be provided with the means to flexibly link digital information with ambient media. To this end we introduce ambient links, which users can embed in web pages to link web-based information with media in their physical surroundings. Explicit control somewhat contrasts with the view of ambient media being a calm technology of which users should not be consciously aware. To address this concern, we present a tool that makes the handling of ambient links in web spaces effectively as simple as the handling of bookmarks. As part of our research, ambient media have been used as an integral part in our everyday work environment, and we have also begun to install ambient media systems in other labs and work groups. We will relate the usage experience gained in our everyday use of ambient media in a discussion of the concepts we introduce. 2. Related Work The research we present in this paper is closely related to the investigation of ambient displays in the ambientroom project, and of abstract representations in the AROMA project. The ambientroom is a mini-office installation equipped with a range of ambient media to explore how these can support the expression of digital information. The installation included water ripples projected to the ceiling, active wallpaper with light patches, and natural soundscapes with modulated density, to display information such as number of unread s or amount of human activity in the workplace. The displays were partly based on standard media but the project also introduced new ambient media devices, e.g. the Water Lamp, whose light shines upward through a pan of water which is activated by changing information, producing changing light patterns on the ceiling [4,5]. Similar to the ambientroom work, the European project AROMA explored new display possibilities, focussing on abstract representations suited for the display of awareness information in the background of our attention. Their prototypes included armrests displaying information in terms of changes in temperature, and background animations of clouds drifting by at varying speeds [6,7]. Our own research is inspired by these developments but less focussed on exploration of new display possibilities; instead our prime concern is the next step: integration of ambient media in information spaces on a larger scale, concepts for identification of ambient media as display for specific information, and support for the flexible use of ambient media. There have been other studies and installations of specific ambient media objects that serve as further sources of inspiration. For example, the artist Natalie Jeremijenko installed the "dangling string" at Xerox PARC, a piece of string hanging from the ceiling and vibrating relative to the traffic load on the local computer network [2]. Another inspiring example is the augmentation of windows with transparent display technology for peripheral display of short-term weather forecasts, based on people's association of exterior windows with the weather [8]. Other examples have been investigated for computer-mediated awareness of remote people, for instance by Kuzuoka and Greenberg who have designed a number of Digital but Physical Surrogates which are tangible representations indicating activity and availability of remote people. Their peek-a-boo surrogate, for example, is a figurine that rotates to face away if the represented person becomes unavailable [9]. Our research relates to the more general theme of moving the interface to information from the H-W. Gellersen, A. Schmi& and M. Beig[

3 desktop into the surrounding environment. This theme is explored, for example, in early ubiquitous computing work at PARC [1], in the ubiquitous media research at the University of Toronto [10] and currently in the design of Roomware at GMD in Darmstadt [11]. Display and interaction media developed in these projects comprise, for instance, electronic whiteboards (Liveboard [1], DynaWalls [11]), situated video units (active hydra units [10]), and interactive table surfaces (InteracTables [11]). In contrast, our work is concerned with the use of non-computer media in our environments for information display, rather than with the use of generic computer and video displays built into the environment. Another theme that our work relates to is the integration of digital world and real world, as expressed for example in the "Tangible Bits" vision of the Tangible Media Group [12]. This theme is explored in early augmented reality projects such as the Digital Desk [13], and in work toward cooperative buildings that integrate information, organisations and architecture [14,15]. We contribute to advance this theme with work on general mechanisms for integration of ambient non-computer media into information spaces, and specifically with the concept of ambient counterparts, designed to build links between digital information and related physically expressed information. 3. Integrating Ambient Media with Information Spaces Earlier work on ambient media has mostly yielded one-of-a-kind installations. One of our goals was to advance this situation and to work toward general mechanisms for integration of ambient media with digital information. To this end, we have developed and implemented the ambient media system, an open architecture for integration of non-computer artefacts as ambient displays of web-based activity. Based on this system, we have integrated various ambient media that support web awareness in our everyday work environments Architecture of the ambient media system The ambient media system we built maximises the use of standard web technology as a commonly available platform. The components of the system are: 9 Standard web server defining a digital information space; 9 Standard web server with common gateway interface (CGI) to serve requests for ambient display. The use of a standard web server and CGI facilitates universal access to ambient media; 9 Web browser for access to documents in the digital information space which in turn triggers requests for ambient display; 9 Non-computer artefacts integrated as ambient media devices, supporting information display through changes in their state and appearance; 9 Media controller for each ambient media device integrated in the system. Media controllers have a software part implemented as CGI program which deals with display requests and keeps track of display state, and a hardware part for the actual device control. The system architecture is shown in Fig. 1. Based on this architecture, web awareness is realised as follows: web pages are related to ambient media by embedding a link to the controlling CGI program in the HTML code. The link to the CGI program is embedded using the image tag, for instance: <IMG SRC=" cgi-bin/light.cgi?increment" width="l" height="l"> Web pages with such embedded links are accessed via the standard HTTP protocol (step 1 in Fig. 1). The server replies by delivering the document to the browser (2). The browser interprets the HTML code, and automatically triggers HTTP GET requests for the embedded images. By this means, the link to the CGI program is followed (3), and the CGI program executed. The CGI program determines the ambient display through control of the connected ambient media device. It does not return any data to the browser. Based on our architecture, new ambient media can be added flexibly, just requiring a CGI program for their control. In our architecture, CGI programs support abstraction from the actual ambient media devices. The CGI programs encapsulate how the devices are controlled. With this mechanism, any ambient media device can be integrated, provided it can be controlled through a defined interface. In the simplest case, very basic devices may be controlled by switching power on and off; more advanced gadgets may be controlled by the power supply (e.g. motor, lights), and rather sophisticated 201 Ambient Media for Peripheral Information Display

4 Fig. 1. Architecture of the ambient media system. 202 appliances may actually be computer controlled, for instance via serial line or home automation buses Implementation of an ambient media environment For further exploration of ambient media in our everyday work environment, we have integrated three types of device in our ambient media system: lamps, a table fountain, and an ultrasonic humidifier as shown in Fig. 2. The lamps used as ambient media are closely associated with artefacts they illuminate, in particular pictures and posters on our office walls and in the hallway. They support ambient display of information by changes in light level, with media controllers for individual lamps as well as for arrays of lamps controlled collectively. The table fountain and the humidifier are positioned in the immediate work space of the authors. The table fountain provides control over four pumps that can be switched on and off independently, supporting variations in ambient display. In our Fig. 2. In our office environment, non-computer devices such as lamps, atabie fountain and a humidifier are integrated as ambient media for display of web-based activity. H-W. Gellersen, A. Schmidt and M. BeigI

5 implementation, the fountain media controller is connected to the device via a parallel interface board, and supports seven different display patterns with different degrees of transience. The humidifier in principle supports continuous change of its state but we use it primarily with a media controller that provides control over three states: off, pulse, and overflowing. With the third one being a particular intuitive display for unusually high levels of activity, according to our experience Discussion The described architecture supports web-based integration of ambient media. CGI programs are utilised as the common interface between the digital system and the physical devices controlled for ambient display. The architecture is clearly geared toward peripheral display of activity in the web, in particular, monitoring and display of page hits and page hit rates. However, it is extensible for awareness of other information beyond web activity, such as awareness of incoming or file system events. The extension can be achieved by integration of event handlers that explicitly call CGI-programs to request ambient display. For instance, in our ambient media environment we utilised the elm mail filter system to trigger calls to CGI media controller depending on evaluation of sender and subject fields. The particular ambient media environment that we installed in our office space proved to be well suited for further investigation. Our usage experience will be related in discussion of further research below. Generally, however it is noteworthy that the chosen ambient media exhibited different characteristics that suggested different uses. Ambient lighting was found to be useful for display of information volume or levels of activity on a continuous scale. The table fountain and humidifier were rather used for notification of events. For events related to unusual high level of activity, users found the overflowing humidifier a particular intuitive display. 4. Relating Information to Ambient Counterparts Given that we have digital information that we would like to monitor in the background of our attention utilising the ambient media concept, the issue is how to identify a suitable ambient medium. Previous work mostly approached this the other way round, first creating a new ambient medium and then considering for what sort of information it might provide a useful display. Some researchers have concluded that matching digital information and ambient media is not straightforward and depends on many factors [4]. In this section we propose one particular approach for relating information to ambient media, not designed to be generally applicable but nonetheless a contribution to move beyond plain intuition in the design of ambient media environments Ambient counterparts According to our experience, much of the digital information we deal with has an intuitive and strong relationship to artefacts that surround us in our physical spaces. For example, we often keep physical versions of digital information such as paper copies of documents, or physical calendar entries. But there are also more abstract matches between digital information and physical objects; for instance, digital product information may relate to products in a showroom, and incoming from family may relate to photos kept on the physical desktop. We suggest that physical objects in such relationships lend themselves to ambient display of the related digital information, and refer to them as ambient counterpart. The relation between digital information and such counterparts may in some cases be obvious, and in other cases be based on individual associations. For example, a postcard from Munich stuck to a pinboard may well be a useful counterpart for digital information on home, vacation, or a friend living there. Multiple instances of digital events can be related to multiple counterparts, in which case a collection of counterparts can be used to display class-based information. In the example, notification of an individual through, say, brief illumination of a related photo would constitute instance-based information display. Alternatively, photos could be illuminated to show who was in touch via over the last week, which collectively would constitute a display of classbased information, expressed as density of light in the personal photo gallery. Class-based information in this case would support an overview of how well family have kept in touch. Class-based information may also support other presentation goals such as comparison or order of events. How media characteristics can be matched with information characterisations such as instance-based vs. class- 203 Arabient Media for Peripheral Information Display

6 204 based is discussed for instance in literature on intelligent multiraedia interfaces (e.g. [16]). To study ambient counterparts, we implemented an application for web site awareness based on our ambient media system. Our particular interest was in ambient display of class-based information to support comparative views of web activity Comparative web awareness based on ambient counterparts In previous work on web awareness it is pointed out that the Web itself is a space where social activity is taking place with people coming and going [17]. This view motivates research into seamless ways of staying aware of activity in our web spaces while being engaged in real world activities. Based on our concept of ambient counterparts, we have developed a contribution to web awareness that provides whole work groups rather than individuals with awareness of web visitors. When we have people visiting our office space we usually get an impression of the projects that interest them in our work environment as they have a look around. For example, they spend different amounts of time looking at the prototypes in our lab, they show different levels of interest in posters and announcements on our office walls, and they selectively pick brochures and papers from our handout material. This inspired us to build an application that similarly would provide us with cues on the interests of our virtual visitors, i.e. people who visit our web site. We use our web site primarily to promote our projects, and found that the related web pages have natural counterparts in the posters in our hallway, which we use likewise for promotion of projects. This led us to the implementation of the web awareness system illustrated in Fig Implementation of comparative web awareness As illustrated in Fig. 3, we installed spotlights in the hallway for control over illumination of project posters. For integration in our ambient media system we built media controller hardware and software. The software part is a CGI program that is executed when a project page in our web site is accessed, based on the use of image tags as described in Section 3. The CGI program communicates the event via serial line to the media controller hardware which is based on a PIC microcontroller. The hardware controls the illumination of each project poster in a way that gives an impression of the number of project page hits over a longer period. This is achieved by increasing the light level a fraction with each hit while slowly fading out the light over time. The rates of increment per hit, and decrement over time can be adapted to the access profile and the desired degree of awareness. For example, relatively fast decrements can be chosen to make changes in web activity over the course of a day or even shorter periods noticeable. Of course, other display strategies are possible. The web awareness system is designed and implemented to convey information not just on individual popularity of project pages in the web, but also on relative popularity. The individual Browser Fig, 3. Comparative web awareness based on ambient counterparts: posters in our office hallway are illuminated to reflect activity in the related parts of our web site. H-W. Gellersen, A. Schmidt and M. Beigl

7 popularity is displayed in terms of how brightly the related poster is lit. Relative popularity can be inferred from the distribution of light over the collection of posters Discussion The described web awareness system has a number of interesting properties. It is accessible to the whole work group, and it is an interesting aspect to also consider the effect on group behaviour beyond individual interaction with ambient media. Members of our work group frequently walk past the illuminated posters in their daily routines, which means that no explicit effort is required to stay in touch with the web awareness information. The awareness information can be perceived literally as we walk by and, in particular, comparative information on web access to different parts of our web site is available at a glance. Effortless access and perception means that the display has the potential to remain in the background of our attention. According to our usage experience, the ambient display is indeed mostly experienced as a background technology that we do not attend to intentionally. When we are busy we walk past the illuminated posters without paying attention. When we have more time we glance at the display. We tend to pay more attention when we expect changes in web access, for example, after announcement of project URLs in newsgroups or press releases. However, with frequent exposure to the display in our daily routine we never walk up to the display intentionally to check its state. Visitors, though, often stop in front of the posters, which frequently prompts casual interaction on matters of web access and relative popularity of projects. This is the case both with first-time visitors who wonder about the different light levels, and with returning visitors with whom the novelty has not worn off as quickly as with us. The display has an interesting effect on the work group as a whole. Similar to the findings in Liechti's personal web awareness system [17], members of our work group experience feedback on access to their web pages generally as rewarding and motivating. However, in our system motivation is not so much drawn from notification of individual page visits but from viewing how popular pages are in comparison to others. In our work group this created a sense of competition to keep project web pages more up to date, to announce them more widely, and to register them with search engines. Our experience, however anecdotal, suggests that comparative web awareness is a useful tool for work groups to draw motivation from feedback on web access. Beyond general motivation, we see a range of applications which can benefit from ambient access to comparative views of web popularity. For example, in electronic journalism, editors could use the approach to stay in touch with how well individual features or columns do. Another example is web marketing, where comparative views of web activity may support competition, and decision making for example on URL announcements. 5. Ambient Links for User Control and Flexibility Overall awareness of virtual visitors in our web spaces as described above is an example of information that continues to be of interest, and that lends itself to permanent ambient display. Generally however we would argue that it depends on the context which information is of interest. At different times people may like to be aware of different kinds of activity in their digital systems, depending on their tasks or changing priorities. For example, with respect to the web awareness application, web site engineers might prefer to use ambient awareness for those parts of their web most recently added or modified. We infer from these considerations that users should be provided with a mechanism empowering them to flexibly link digital information to ambient media available in their physical workplace. We introduce such a mechanism - ambient links - and a tool supporting simple creation and deletion of such links Ambient links Ambient links define a relationship between an event in the digital world and a display operation of an ambient medium in the real world. The same digital event may be linked to different ambient displays, and the same ambient display may be linked to different events. The notion of such links is implicit in integration of ambient media with information spaces as discussed in Section 3. However, with consideration of user control over their ambient media environment, we think of ambient links as the mechanism to connect the user's personal information space with their personal work environment. Control over creation 205 Ambient Media for Peripheral Information Display

8 and deletion of ambient links empowers the user to adapt and to individualise their ambient media environment. Ambient links generally introduce flexibility in the sense that decisions on choice of media can be taken at run time rather than only at design time. This flexibility is important, as we agree with other researchers claiming that design choices on ambient media are far from understood but clearly depend on users' tasks and preferences [4]. Explicit control potentially burdens the user, and is somewhat in conflict with the goal of providing ambient media as a calm technology at the periphery of our attention. Therefore, creation and deletion of ambient links should be simplified as far as possible through provision of tools. For instance, in the shown screenshot, a conference web page has been selected to get notification on virtual visits. The fountain is selected as ambient medium, and five seconds of bubbling is selecting as display operation. After selection of the web page, ambient medium and display effect, an ambient link is established by pushing the create button. This actually leads to insertion of a piece of HTML code into the selected web page, using the image tag as already described above: <IMG SRC=" karlsruhe.de/ cgi-bin/fountain.cgi?bubbles" width="l" height="l"> An editor for ambient links In our work environment we use ambient media mostly in conjunction with the web, and in analogy to simple interaction with web pages we wanted to make ambient linking as simple as bookmarking. With this analogy in mind we impleraented the ambient link editor shown in Fig. 4. With the editor, users can browse through web sites to select web pages they wish to monitor in their ambient media environment. From the Ambient Media menu, they can select one of the available devices, and from the Action menu they can choose among the supported display operations. Note that insertion of this code in any web page in the World Wide Web would result in our table fountain bubbling for a moment whenever that page is accessed. The effect is not restricted to local web pages but, of course, the creation of ambient links is restricted to pages for which the user has modification rights Discussion In our work group, ambient links have been used in the context of personal information management, and for flexible awareness of activity in a conference web site that we had set up for the Fig. 4. An editor for user-controlled creation and deletion of ambient links between events in the digital world and display effects in the physical work environment. H-W. Gellersen, A. Schmidt and M. Beigl

9 First International Symposium on Handheld and Ubiquitous Computing (HUC'99). We found that the user control and flexibility provided by ambient linking was mainly utilised for two kinds of application: short-term assignment of ambient media for notification of expected events, and monitoring of processes that involve different information in successive phases. Short-term assignment of ambient media was frequently used for notification of expected events. For example, one of the authors always used ambient media, more specifically his table fountain, to monitor access to documents he made available to project partners via the web. His fountain would bubble for a certain period after document access and, depending on his situation, he might notice and check who accessed, might notice and ignore, or might not even notice at all. This means the importance and concentration assigned to a foreground task would control the level of attention for the peripheral display. Flexible ambient linking was also found to be useful for monitoring processes that involved different activities at different stages. For example, we used ambient media to monitor activity on our HUC'99 conference web site. In the process of conference preparation, different pages were of interest and monitored with ambient media (light for impression of access rate, and fountain to notify each access). First the general announcement, at a later stage access to submission details, then access to the submission form, and so on through the review process and finally through registration which were all web-based. At all stages, the ambient feedback was found extremely useful. In the earlier stages, it provided feedback on success of announcements, and influenced timing of follow-up calls which we posted whenever access rates subsided. At later stages, it was helpful, e.g. to keep track of whether reviewers picked up the papers they been assigned and, finally, ambient notification was particularly motivating when delegates registered through the web. At this stage, each time the table fountain bubbled in our office we did feel a tremendous sense of reward. Compared to our experience with permanent ambient displays described in the previous section, we found - not surprisingly - that users pay more attention to ambient media they themselves select. Nonetheless, as soon as users deal with other tasks, their ambient media move into the background of their attention. The described experience backs up our case for flexible and user controlled ambient linking, however it will have to be investigated whether and how less involved users than ourselves would use ambient linking. Another interesting issue to be studied is user control over ambient media in shared work environments. For example, ambient displays perceived as calm by one user may be experienced as obtrusive by another. 6. Summary Previous work has considered the use of our physical work environments for peripheral display of digital information. The term ambient media has been introduced for media in our surroundings that display information as changes in physical state and appearance. In this paper, we have further explored ambient media to address the integration of ambient media in information spaces, the mapping of information to ambient media, and the flexible creation and deletion of ambient links. We have introduced the ambient media system as an extensible integration platform, the notion of ambient counterparts, and a mechanism for flexible use of ambient media. The introduced concepts have been implemented, applied and extensively used in our own work environment. Ambient counterparts have been studied in a web-awareness application, demonstrating their collective use for the display of class-based rather than instance-based information, facilitating a comparative view of web activity. The application led to interesting observations of how the group and visitors interact with peripheral displays, and of effects on group motivation. The group greatly valued the information that was made available via peripheral display. This is interesting, as in principle they could have accessed the same information from log files but had rarely done so. Obviously, it required the subtle presence of the information in their work environment to stimulate their own awareness. Once this awareness was established, the ambient comparative view of web activity even stimulated a sense of competition within the group to keep their web pages interesting and accessible. In other applications - personal information management and a conference web service - we studied the use of ambient links to flexibly connect digital information to ambient displays. In this context we found that flexibly-assigned ambient media are well suited for notification of expected events, and for monitoring of processes that involve different information. With the more intentional 207 Ambient Media for Peripheral Information Display

10 208 use of ambient media in these applications, they were sometimes rather perceived as tools than as part of the environment. Nonetheless, they remained in the background of our attention, and we observed that the ambient display was simply ignored if foreground activity required our undivided concentration. From our experience in the daily use of ambient media, we conclude that they can be a very valuable extension to our digital information spaces. They are particularly useful to display information that is not critical but motivating. It is also evident from our experience that ambient media improve accessibility and help promote awareness of information. However, it will have to be studied how other user groups would interact with ambient media environments, and whether ambient media would be accepted as useful augmentation of our work environments rather than as cool technology. We also see need to further develop a general understanding of how information can be mapped to presentation media. Finally, based on our experience with ambient web awareness, we would also propose research into codesign of web information spaces and office spaces, to create novel work environments for interaction with information. References 1. Weiser M. The computer for the 2P t century. Scientific American 1991; 265(3): Weiser M. Brown JS. Designing calm technology. Powergrid Journal 1.01, /calmtech.html 3. Wellner P, Mackey W, Gold R (Eds). Computer-augmented environments: back to the real world. Communications of the ACM, July i993; 36(7) 4. Wisneski G, Ishii H, Dahley A, Gorbet M, Brave S, Ullmer B, Yarin P. Ambient display: turning architectural space into an interface between people and digital information. In: Streitz NA, Konomi, S, Burkhardt H-J. (eds). Cooperative buildings. Proceedings of the First International Workshop on Cooperative Buildings (CoBuild '98), Darmstadt, Germany, February 1998; Lecture Notes in Computer Science 1370; Springer-Verlag, Heidelberg; Ishii H, Wisneski C, Brave S, Dahley A, Gorbet M, Ulhner B, Yarin E ambientroom: integrating ambient media with architectural space. CHI'98 Video Program; ACM Press, New York, Pedersen ER, Sokoler T. Awareness technology: experiments with abstract representation. Proceedings of HCI International '97, San Francisco, August 1997; Elsevier 7. Pedersen ER, Sokoler T. AROMA - abstract representation of presence for the purpose of mutual awareness. Proceedings of CHI '97, Atlanta, 1997; ACM Press, New York: Rodenstein R. Employing the periphery: the window as interface. CHI '99 Extended Abstracts, Pittsburgh, May 1999; ACM Press, New York: Kuzuoka H, Greenberg S. Mediating awareness and communication through digital but physical surrogates. CHI'99 Extended Abstracts, Pittsburgh, May 1999; ACM Press, New York: Buxton W. Living in augmented reality: ubiquitous media and reactive environments. In Finn A, Sellen A, Wilber S (eds) Video mediated communication. Lawrence Erlbaum Associates Inc., Hillsdale NJ, Streitz NA, Geigler J, Holmer T. Roomware for cooperative buildings: integrated design of architectural spaces and reformation spaces. In Lecture Notes in Computer Science 1370; Springer-Verlag, Heidelberg 12. Ishii, H, Ullmer, B. Tangible bits: towards seamless interfaces between people, bits and atoms. In: Proceedings of CHI '97, Atlanta GA, March ACM Press, 1997; Wellner R Interacting with paper on the digital desk. Communications of the ACM, July 1993; 36(7): i4. Streitz N A, Konomi, S, Burkhardt H.J. ( eds ). Cooperative buildings. Proceedings of the First International Workshop on Cooperative Buildings (CoBuild'98), Darmstadt, Germany, February 1998; Lecture Notes in Computer Science 1370; Springer-Verlag, Heidelberg 15. Streitz NA, Siegel J, HartkopfV, Konomi, S. (eds). Cooperative buildings. Proceedings of the Second International Workshop on Cooperative Buildings (CoBuild '99), Pittsburgh PA, USA, October 1999; Lecture Notes in Computer Science 1670; Springer-Verlag, Heidelberg 16. Maybury M. (ed). Intelligent multimedia interfaces. AAAI Press, Menlo Park, Liechti O, Sider N. Ichikawa T. A. Non-obtrusive user interface for increasing social awareness on the World Wide Web. Personal Technologies 11999; 3 (l&2): Correspondence to: Hans-W. Gellersen, Albrecht Schmidt and Michael Beigl, Telecooperation Office, University of Karlsruhe, Vincenz-Priegnitz-Str. 1, Karlsruhe, Germany. hwg@teco.edu; H-W. Gellersen, A. Schmidt and M. Beigl