What are clusters?
==================
* a set of connected documents 
* held together by a spanning tree
* clusters have a minimum size (absolute? relative? relative to what?)
* clusters do not break when removing a single bridge (or maybe
  a small amount of bridges)
* ???

What are bridges?
=================
* bridges connect 2 clusters
* of any type except before, sameDate, after, equivalent

What are hubs?
==============
* Hubs have a lot of outbound associations of directed type
  (except temporal associations - in most cases cites will occure)

What are authorities?
=====================
* Authorities have a lot of inbound associations of directed type
  (except temporal associations - in most cases cites will occure)


What are collapsing trees?
==========================
* Leafs represent documents.
* Inner nodes represent topics.
* (Deeper nodes represent more specific topics - maybe?)
* Siblings are all connected to each other (transitive?)
* Bigger transitive clusters always collapse first.
(* The topics stop collapsing when collapsing gets ambigous?)
(* The roots of these trees remain connected as networks?)

What are clustertrees?
======================
* Clusters are nodes in these trees.
* The level of the tree corresponds to the amount of removed bridges.
* The sum of the siblings (and their erased bridges) correspond to 
  their father.
* The number of child nodes is always selected to producethe maximum of 
  ( cnt(child) 
  x ( NrOfParentDocs/cnt(child) 
    - ( MaxNrOfChildDocs-MinNrOfChildDocs ) 
    )
  ).


Comparing collapsing trees and clustertrees
===========================================
* Leafs of collapsing trees are contained in nodes near root  of 
  clustertrees.
* Leafs of clustertrees are contained in nodes near root  of 
  collapsing trees.
* How big is the beak even point?
* 