TABLE OF CONTENTS This chapter describes how location information is produced, transported, and consumed on the Internet. This includes the presence model and the GEOPRIV abstract model for location services and privacy.
A presence service provides a way of accessing information about an individual's status. This is possible because an individual publishes information about themselves to the service so others can acquire that information.
Presence evolved from instant messaging services, providing users with a way of finding where their friends were on the Internet. Presence information for instant messaging includes details on how to contact a user that is, whether they are online and what their current network location is. Since this initial form, a range of presence applications have been defined and presence is now used to convey a wide range of user data.
The presence model is defined in Reference 1 (at the end of the chapter) by three roles: a presentity, a presence service, and a watcher. Figure 2.1 shows this very simple model.
The presence and GEOPRIV models are abstract concepts, which means that the ideas they define do not always directly relate to real-world concepts. Instead, they define a set of roles and the interactions between those roles. Each role is defined by a set of tasks that it performs. When an abstract model is applied to a real situation, each participant assumes one or more roles.
The presence service is a...
