Abstract
Internet applications nowadays are part of our everyday life. Gathering information from any networked site in the world, exchanging documents, transferring information via e-mail, telephone and video conferencing, e-learning or Web shopping are well known examples for Internet collaboration. The common characteristic of all these activities is the elimination of the spatial distance between involved partners. Furthermore, the information can be accessed with different devices, from hardwired PCs via WLAN-capable notebooks and PDAs (Watters, 2003) to mobile phones. The introduction of wireless communication in recent years opened new opportunities for collaboration based on so called location-based services (Schiller, 2004; Jagoe, 2003). These benefit from the fact that the most wireless devices need a dedicated access point to connect to the network. This access point registers all users in the neighborhood, and thus adds new information relevant for communication: the current spatial position of the device and its user. All registered users/devices create a local neighborhood for ad-hoc communication. This scenario is very common in our everyday life: People contact other people at different locations and start a conversation. Furthermore, they often share documents to learn (e.g., lecture slides), for entertainment (e.g., holiday photos) or¾most common¾to collaborate and to develop products in a team. All this is possible in the Internet, too, and countless applications were developed in recent years. However, each user has to know the persons to be contacted a-priori and have the access information available¾for example, e-mail address or ICQ number¾before the first contact. In opposite, users in the local neighborhood can approach other members without knowing each other a-priori. The partners must declare their willingness for communication; for example, by installing a client program and setting the security parameters accordingly. In summary, the restriction to a local neighborhood or the consideration of the current location is opposite to the main design idea of the internet to bridge the gap between spatially divided users and resources. However, this approach aims to satisfy human needs to learn more about their current local environment, the infrastructure and the people in the near neighborhood. Therefore, peer-to-peer-based collaboration platforms allow a location-based selection of relevant information and ad-hoc communication with users in the range of the current access point.