Developers Introduction

The Case class is the heart of the CIME Case Control system.  All
interactions with a Case take part through this class.  All of the
variables used to create and manipulate a case are defined in xml
files and for every xml file there is a python class to interact
with that file.  

XML files which are part of the CIME distribution and are meant to
be readonly with respect to a case are typically named
config_something.xml and the corresponding python Class is
Something and can be found in file CIME.XML.something.py.  I'll
refer to these as the CIME config classes. 

XML files which are part of a case and thus are read/write to a
case are typically named env_whatever.xml and the cooresponding
python modules are CIME.XML.env_whatever.py and classes are
EnvWhatever.  I'll refer to these as the Case env classes.

The Case Class includes an array of the Case env classes, in the
configure function and it's supporting functions defined below
the case object creates and manipulates the Case env classes
by reading and interpreting the CIME config classes.