  Whenever a large group of people are engaged in an activity, communities will
form. The nature of these communities depends on the relationship considered.
In the group of people who regularly use scholarly literature, a relationship
like ``person i and person j have cited the same paper'' might reveal
communities of people working in a particular field. On this poster, we will
investigate the relationship ``person i and person j have read the same
paper''. Using the data logs of the NASA/Smithsonian Astrophysics Data System
(ADS), we first determine the population that will participate by requiring
that a user queries the ADS at a certain rate. Next, we apply the relationship
to this population. The result of this will be an abstract ``relationship
space'', which we will describe in terms of various ``representations''.
Examples of such ``representations'' are the projection of co-read vectors onto
Principal Components and the spectral density of the co-read network. We will
show that the co-read relationship results in structure, we will describe this
structure and we will provide a first attempt in the classification of this
structure in terms of astronomical communities.
  The ADS is funded by NASA Grant NNG06GG68G.
