A picture of the user interface presented by the modified
xrn is shown in figure 
. When users start up
the program, two windows appear on their screen: the main window
(shown on the right of the figure) and the filtering control panel
(shown at the upper left of the figure). The main window appears as
it does in the unmodified version of xrn. All the controls
for the collaborative filtering system appear in the control panel
window. This allows users who do not want to bother with the
filtering system an easy way to dismiss the filtering controls, while
still reminding them that the system is there.
Consistent
with the rest of the xrn interface, as the user moves the
cursor over the buttons and toggles of the control panel, they are
shown short help messages explaining what the button or toggle does.
More detailed information on the collaborative system is available by
selecting the ``Info'' button.
Figure: Portion of xrn main window showing a list of
available articles sorted by order of popularity. The numbers in `()'
represent the number of positive and negative votes received by the
articles.
Figure: Interface for the xrn news reader client. Main
window on right, filtering controls on left.
When the user enters a newsgroup to read the articles
available in it, the current filtering mode is used to determine how
the available articles are presented to the user. In the ``normal''
filtering mode, articles are presented to the user without any
changes by the filtering system. In the ``Only popular'' filtering
mode, only articles that have been judged to be popular by the system
are displayed to the user. In the ``Popular first'' mode, the
articles are sorted by order of popularity. Articles receiving the
most votes are placed at the top of the list of available articles,
and articles receiving no votes are placed at the bottom of the list.
Articles receiving mostly negative votes are placed together in a
block after the articles which received positive votes, but before the
articles that have received no votes. In both the ``Popular first''
and ``Only popular'' modes, articles are presented to the user along
with numbers indicating how many people have voted for and against the
article. These rating numbers are to help the user gauge the importance or
relevance of the articles (see figure ).
Users can vote on an article at any time while they are reading it by clicking on the ``Great,'' ``Good,'' or ``Bad'' buttons. If the user has set the ``Auto advance'' feature, they will be automatically taken to the next screen or next article when they vote on an article. This means that reading and voting for an article takes no more mouse-clicks than just reading it would - a feature which we believe substantially streamlines the interface.
As people first begin to use the collaborative filtering
system, very few of the available newsgroups will contain any articles
that have been voted on. To help users find newsgroups which have
collaborative filtering information available, we created the `group
list' menu shown on the bottom left of figure . This
menu is opened from the filtering control panel and shows all the
groups for which some filtering information is available. If a user
clicks on a listed group, the user is immediately taken to that group
and shown the available articles in the group. The goal is that by
helping users find the groups in which some votes have already been
cast, we can help those groups quickly achieve a critical mass of
users.