Class Summary  9/4/95

        Group 2:
                Lauren Barton
                Martin Falck
                Nelson Kile,Jr.
                Carolyn O'Hare
                Robert Ryan

  We spent a challenging 40 minutes or so trying to get the
videoconference
system to work, then spent more time on administrative details.
Fortunately,
we finally found time for the lecture.
     Todays lecture was on inverted file systems.  After an overview of
the binary document term matrix , along with the problem of space
requirements, the discussion led to the inverted file systems
used in most IR systems. The FAST-INV algorithm was used as an
example
of an actual IF system, taking into account memory considerations and
efficiency.
   The next topic was the use of bite vectors versus hash tables,
and the average and worst-case scenarios for each.  Hashing
algorithms along with methods of handling collisions was also discussed.

The Ziff distribution was used to demonstrate where some methods
would be most efficient.
   We then discussed the construction of Boolean queries, using the
Disjunctive and Conjunctive forms.  These can be converted back and
forth
using algebraic manipulation.
   At this point the video system froze and we assumed class was over.