This directory contains the classes that form the data model of Kyua.

The classes in this directory are intended to be pure data types without
any complex logic.  As such, they are simple containers and support the
common operations you would expect from them: in particular, comparisons
and formatting for debugging purposes.

All the classes in the data model have to have an on-disk representation
provided by the store module; if they don't, they don't belong in the
model.  Some of these classes may also have special behavior at run-time,
and this is provided by the engine module.
