A browser maintains a position within a hierarchy and
moves that position by handling picks on lists of 
choices.  

''Therefore:''  Be clear about what hierarchy is being
navigated. Avoid the temptation to navigate more than
one hierarchy or to maintain more than one position in
a single hierarchy.

Use LeftSelectsRight to visualize the path taken to
a specific point in the hierarchy.

The browser is not a good model for operations that
take place between two hierarchies or two points within
a single hierarchy.  CutAndPaste or DragAndDrop between
two independent browsers provides a better model for 
organizational operations like ''move''.

-- WardCunningham

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On the other hand, a control that allows the browser to switch 
to another hierarchy, discarding information about the current
hierarchy, still fits the pattern and can be useful in some
circumstances.    I built a Cross Reference Cards browser that
handled a stack of cards with links.  Only one stack could be
browsed at a time, but one could switch to a different stack.

-- JoeDavison

see MultipleCategorizationPattern