1.1.4. Push and Pull Services

In general one can distinguish two different kinds of location services considering if information is delivered on user interaction or not:

Pull services deliver information directly requested from the user. This is similar to call a website in the Internet by fill in its address in the web browser-address field. For pull services a further separation can be done into functional services, like ordering a taxi or an ambulance by just pressing a button on the device, or information services, like the search for a close Chinese restaurant (Virrantaus et al. 2001).

Push services deliver information which are either not or indirectly requested from the user. Such push services are activated by an event, which could be triggered if a specific area is entered or triggered by a timer. An example for an indirectly requested service is a news service subscription which contains event information with respect to the actual city. A not requested service could be advertisement messages if a specific area in a shopping mall is entered or warning messages if weather conditions change (e.g. hurricane warnings). Since push services are not bound on previous user interaction with the service, they are more complex to establish. Here, the background information like user needs and preferences have to be sensed by the push system.