Upcoming major overhaul for LISA

Greetings. LISA's most recent bug report, involving a subtle problem in the
Rete network, has sparked some serious thinking on my part. When I first
started the project I 1) read Forgy's paper for an introduction; 2) closely
studied two existing Rete implementations (Jess, CLIPS); then 3) borrowed
heavily aspects from both and put together a CLOS implementation. The plan
was to use this initial version as a testbed of sorts until I thoroughly
understood the algorithm, but LISA acquired some early users and I
concentrated on feature work instead. Now I find myself with a bug in an
area of LISA that falls into the "why was this particular design path
chosen", and I can't answer that question and can't immediately solve the
problem.

So, I have decided it's time to overhaul the project. I'm going to do
several things:

1. Branch the development tree and create a LISA 4.0 path.

2. Reorganize the code base such that it will support multiple matching
algorithms (much work here).

3. Return to Forgy's original paper and write, from scratch, a "reference
implementation" in CLOS that represents the essence of Rete without some of
the later optimisations used by Jess/CLIPS (node sharing, etc.). I'll
maintain the fast join node memories, but that's it for optimisation in the
RI.

4. By this time I should completely grok Rete and be able to enhance and fix
LISA's current algorithm.

Once these things have been done LISA will be in a position to support other
algorithms; experimental versions of Rete, TREAT (maybe), whatever. They
will simply "plug in" to the engine framework and "just run" ;-)

Now, what is the impact here? I intend to suspend all work on 1.x; there
simply is no time to do the overhaul plus add new features to that trunk.
This probably means no more bug fixes to 1.x unless someone is *really*
desperate. Since that's not likely I don't anticipate a problem here.

How long? Dunno. I've less time now than I used to, but this upcoming work
is interesting, fall and winter are coming, etc. So, that's it. Feel free to
comment, if you like.

Regards,
--
------------------------------------------
David E. Young
[email protected]
http://lisa.sourceforge.net

"Those who expect to reap the blessings of liberty
 must undergo the fatigues of supporting it."
  -- Thomas Paine

"But all the world understands my language."
  -- Franz Joseph Haydn (1732-1809)




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