For a general purpose awareness environment it is important to provide its services application independent. It is not sufficient to present awareness information just within an application. Consequently relevant events about user activities should be externalized from one application and promoted to other applications. Thus users can stay aware about important events and activities even if they are not actually using or running a particular groupware system. This should include events from real world and electronic settings.
The conceptual model of NESSIE is based on the approach that information about cooperative actions that are relevant for the awareness of the state of a cooperative setting can be captured through the generation of events. Events are generated by sensors that are associated with actors, shared material, or any other objects that constitute or influence a cooperative environment. Sensors are not restricted to electronic environments, physical sensors to capture activities in rooms through movement and noise sensors can also be integrated.
After creation, an event is transmitted to an awareness server. An important task of this server is the propagation, transformation, and notification of events. The presentation of awareness information to users is performed by configurable indicators. Figure 1 illustrates the architecture of the NESSIE awareness environment. Central components are the NESSIE server in combination with the event database and the NESSIE client. The server supports two methods for the submission and notification of events: asynchronous (pull) server interaction by a cgi-interface or synchronous (push) notifications based on registered interest profiles by the NESSIE client.
A very simple technique is provided for the interacting with the server using cgi scripts (left hand side of Fig.1). This interface allows the submission of events via http-calls of a cgi script. The script interprets the call parameters that consists of attribute-name/value pairs, as a event descriptions. With the cgi- interface for event submission and retrieval the NESSIE environment can be easily integrated as an application independent awareness bridge into legacy infrastructures. Dynamic event types are a key factor for scalability and enable the application of NESSIE in different organisational boundaries. However, the http solution embodies the disadvantage that applications must explicitly pull the NESSIE server for new events. Accordingly, this mode of operation can not be used for settings where events must be immediately processed or indicated, but provides appropriate means when loosely coupled interactions are sufficient. Therefore we have introduced the NESSIE-client.