IntroductionSocial Functions of Post-Its, Graffiti and PostersA More Social Location-Based Information System?Interaction RequirementsImplementationRequirementsClientServerConclusionsAcknowledgmentsReferencesG. D. Abowd, B. Brumitt, S. A. N. Shafer (Eds.): Ubicomp 2001, LNCS 2201, pp. 2-17, 2001. Springer-Verlag Berlin Heidelberg 2001GeoNotes: Social and Navigational Aspects of Location-Based Information SystemsFredrik Espinoza, Per Persson, Anna Sandin, Hanna Nyström,Elenor Cacciatore, and Markus BylundHUMLE Lab, Swedish Institute of Computer Science (SICS)Box 1263, 164 29 Kista, Sweden{espinoza,perp,sandin,hannan,elenor,bylund}@sics.seAbstract. Location-based information systems allow the user to accessinformation in relation to the user’s position in geographical space. Thispaper outlines navigational and social aspects of such systems. It isargued that location-based systems must allow users to participate ascontent providers in order to achieve a social and dynamic informationspace. Moreover, as these systems allow commercial and private usersto annotate space with information on a mass-scale, informationfiltering techniques will become essential in order to preventinformation overload and user disturbance. We present a number ofcontent-based and social filtering techniques to support this. We discussimplications for implementation and we describe a system (GeoNotes),which takes some of these aspects into account.1 IntroductionSome location-based systems are centered on the notion of positioning people inrelation to each other (e.g., [12]). Location-based information systems, on the otherhand, position information. The basic idea is to connect pieces of digital informationto a specific latitude-longitude coordinate via some mobile device, thereby ‘attaching’them to a specific place in space. Later, users, again via some mobile client, canaccess that information. In this way, users will get the impression that the digitalinformation is actually attached to a place in a way similar to post-its, graffiti andpublic signs and posters.Quite a few systems have been working with this basic concept over the last fiveyears within the fields of augmented reality, wearables and ubiquitous computing [8;3;1;16;20;7,18,4]. Some have used goggles as access medium [21]. Most, however,work with handheld devices, that may not provide the same stunning and spectacularvisual effects, but still preserve the basic functionality.It is our intention not to repeat the results of these projects, but rather to discuss thecommunicatory, social and navigational implications of the mass usage of a location-based information system of this kind. We believe that the space of location-basedinformation needs to be free for all users – not only professional content providers.GeoNotes: Social and Navigational Aspects of Location-Based Information Systems 3Moreover, once we allow for mass-annotations, this will impose serious designchallenges in terms of navigation and filtering. In the same way as the World WideWeb user eventually needed a wide range of navigation support (e.g. search engines,collaborative filters, news-groups, link lists, index views, navigation bars, and “web-tips” in the press), so will users of location-based information systems.First we discuss the communicatory and social functions of ‘traditional location-based information systems’, such as post-its, graffiti and posters. In the light of this,we then analyze some features and social shortcomings of digital location-basedinformation systems, and present a more social emphasis for location-basedinformation systems. Next, we address the design implications/requirements for sucha social location-based information system in relation to the user’s interaction withand experience of the system. Finally, we present an implementation – the GeoNotessystem – that tries to address these design challenges.Thus, the purpose of the paper is twofold. On a theoretical level, it seeks to analyzethe social aspects of location-based information systems, and propose design solutionsto support those aspects (both on a user-oriented and a technical level). On the otherhand, we also present a system that goes some steps in the direction of the design wesuggest.2 Social Functions of Post-Its, Graffiti and PostersAlthough location-based information systems need not slavishly replicate the featuresof paper post-it notes, graffiti, signs and posters, such technologies may providedesign inspirations for their digital counterpart. In particular, their communicatoryand social functions may provide insights.Although they do not adhere to all surfaces, post-it notes stick to almost everythingin an indoor environment. Other than primitive sketches, multimedia content is notpossible. However, they are dispensable, cheap and easily accessible. Since creatorand reader share the same spatial context, the message can rely on short deicticexpressions such as ‘Make 10 copies of this!’ without loss of understanding. Suchreferencing can be quite exact since the note can be placed on rather small objects(e.g., pieces of paper, computer screens, mugs). Post-its are mostly used betweenpeers and colleagues who know each other’s habits, preferences, sense of humor andpersonality quite well. By exploiting and alluding to this shared context, messagesneed not be that long to contain much valuable information. Moreover, post-its needno greetings or wrapping up phrases as e-mails do.At work, post-its are used to coordinate and plan tasks in order to make work moreefficient. Reminding oneself and others is a central communicatory function of post-its. In domestic environments they can have additional expressive and social bondingfunctions (e.g., ‘Good morning! I love you very much!’). Such communication maybe less ‘serious’ and task oriented, but may in fact constitute the most common usageof post-it technology.While post-its are oftentimes directed to individuals and peers, graffiti - which canbe both textual and graphical in nature - is mostly anonymous and intended for amass-audience (‘Stop the deforestation! Stop eating at McDonalds!’). Because of this,graffiti is annotating public rather than domestic places, for instance public restrooms,4 Fredrik Espinoza et al.walls, buildings, and public transportation. Often it has a strong expressive function interms of emotional reactions, social and ethnic identity, politics, prejudices,