iple inheritance as efficient as classes of the <code>base</code> model.
Other advantage of the cache model is that meta-methods like the <code>__index</code> can be shared across the hierarchy of classes because they are copied to each class (<i>i.e.</i> meta-table).
Currently, Lua ignores the <code>__index</code> when accessging the fields of meta-tables (see the <a href="http://www.lua.org/manual/5.1/manual.html#2.8">Lua manual</a>).</p>

<p>On the other hand, to properly update the cache of inherited fi