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Effective when
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user doesn't know the name of the target.
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a user wants to browse --and find things they didn't know about
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topics have hierarchical structure -- not too broad, not too
deep
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not too exclusive so that almost anything might be found in
almost any heading
Weakness: when there is no real hierarchy -- no depth
to any of the headings -- so broad without any depth
Design issue: when you set up a topic list you want to allow
for extendability so you must choose a general topic structure that
allows new items to be added but is not too inclusive to allow anything
to be added.
Consistent: there should be some consistent organizing principle,
so that even if on the surface the collection of topics seems arbitrary
reflection reveals there is a deeper organizing principle. E.g.
in a hierarchy the children are specializations of their parent,
so there are fewer elements that fall under the child category than
under the parent category.
Most hierarchies are really derived from lattice structures.
In a lattice a given node may have more than one parent. That
means that when this is converted to a hierarchy, as in a family
tree, the same node can appear as a sub-topic of more than one high
level topic. I appear in the family tree that starts with my great
grandmother on my mother's side, and I appear in the family tree
that starts with my great grandmother on my father's side.
Exercise: find a few examples of sites with topic structures
that are really based on lattices.
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