The very first time a user uses this system, the user can either create an
agent from scratch, or use off-the-shelf agents created by someone else. The
way to do this is explained in Section 
.
For the purposes of this section, assume that the user already has a set of
agents.
At start-up, the Main Window consisting of a number of filtering agents appears
on the screen (see figure ).
Each agent is visually represented by a graphical icon (the Agent Icon). Each
agent is responsible for retrieving interesting news articles from some particular
news domain. Below each of the Agent Icons is a set of 3 small icons, bearing
the signs ``+'', ``-'' and ``?'' respectively. These are for providing positive/negative
feedback and to ask the agent to explain its actions (see Section ).
Each agent is assigned a particular color, which is used to visually identify
the graphical elements belonging to the agent. The background color of the three
icons (``+'', ``-'', ``?'') is the color code of the agent.
A menubar is provided to enable manual browsing and for manipulating agents (see following Sections on Manual Browsing and New Agents).