In Elastic Windows, windows are rectangular with a content area surrounded by borders on each edge. Hierarchy is indicated by the nesting of window borders where lower-level windows are surrounded by the borders of higher-level windows.
Within a group, windows at the same level can be organized in
alternating horizontal and vertical tilings (Figure 
).
Windows within a group are considered at the same level even when
there is a mixed order of horizontal and vertical tilings unless they
are surrounded by a higher-level window. This gives users flexibility
in the organization of windows to some degree, avoiding strict
stacking of windows within a group.
Any feasible layout in Elastic Windows can be described by a sequence
of cuts such as 
,
where each cut 
partitions window 
into two
rectangular windows 
and 
horizontally or vertically
and is created by a cut 
. Thus, there are
layouts that can not be designed in Elastic Windows
(Figure .c).
In Elastic Windows, tiled window organization is chosen primarily in order to maximize the visibility of windows. According to my observations, people typically try to organize related windows of a task non-overlapping, even when overlapping windows are allowed. As Cohen et al. [70] stated, overlapping window layouts are difficult to handle when large numbers of windows must all be visible at once, and they come and go rapidly. On the other hand, in space-filling tiled approaches, window contents may not always conform to different window sizes and small window sizes may not provide sufficient view of window contents.
However, for tasks dealing with only a single window, overlapping
windows approach is beneficial. Thus, the Elastic Windows approach has
been applied to overlapping and non-spacefilling non-overlapping
window organizations (Figure ).
