Chapter 6: User Interfaces for Mobile Media 259 As the number of objects that needs to be presented is often high, the columns are narrow so as to display as many objects as possible. The currently highlighted object and the two subsequent objects form a so-called lens, which shows the items enlarged in order to reveal more details, while the rest are displayed as lines only. The cell value of a selected attribute and the object is displayed in the message area below the table. In addition to the table view, Matrix Browser provides a more tra- ditional list view for viewing the current object and its associated metadata in detail. Furthermore, the user may select an attribute and edit its value in the list view. The user manipulates the matrix by chang- ing the order of the rows in order to indicate the importance of an attribute (the topmost row is the most important). Furthermore, the user can sort the columns in descending order by using the attributes as a sort key, which makes the leftmost column the best result. Matrix manipulation lets the user explore the data and fi nd dark blue areas in the matrix, in order to discover attributes with mutual dependencies. Row selection may be toggled on and off by using, for instance, a number key on the keypad, associated with a row number. The location of selected row(s) can then be changed with up and down cursor keys. The lens is moved with left and right cursor keys and the columns are sorted to descending order with the “ ” key; fi nally, the * “#” switches between the views. Matrix Browser can also be used for other purposes, for instance, visualizing a result set of a web search query that is based on several search terms. Then the rows will present the search terms and columns result pages. Each cell will then display how many times the search term has been encountered on the page. The darker the colour, the more hits on the page. As Matrix Browser and Media Tray illustrate, it is important to allow the user to interact with the view, for instance, to fi lter out irrelevant content, or to change the sort keys and order. The user should be able to change the presentation technique, for instance, in a map-related application it may be useful to browse all the points of interest (POIs) as an alphabetical list, but it may also be useful to see them overlaid on a map (personal content and location information is discussed in detail in section 7.2). Metadata is often considered additional information that should be hidden from the user, unless they explicitly wish to view it. Neverthe- less, there are occasions when the metadata attribute and its value should be displayed and it can also be available for editing attributes such as date, time, keyword, rating, annotation, and comment. If visible, the metadata is displayed mainly as a text string (such as