How is MAT data used?

[John T Stein]

By way of introduction (since that seems to be de rigueur for initial 
list postings) I am an electrical engineer dealing primarily with 
analog circuit design.  I can possibly contribute to this list in the areas of 
sensor signal processing and EMI management.  My hands-on involvement
with cars is considerably less intense than  most of you, I'm sort of a
 "'shade-tree mechanic with an oscilloscope" but I AM interested in 
the technology.

In the past I have seen numerous postings to this list that discuss 
how data from throttle position sensor, battery voltage, etc. are 
employed to modify the baseline injector pulse width.  Could someone 
please explain how MAT data is used?   Also, on a "learning" ECM such
 as is used on my 2.5 L GM engine,  are the baseline pulse widths typically
altered based on the long-term readings of MAT??