A *(term) for, simply stated, a set of rules for manipulating and communicating with _(meta-object)s. In other words, it's a _(metaprogramming) library, or even a language in its own right, which the _(Lisp) family of languages provides rather simply with the language itself. The Mjlner _(Beta language | Beta) system provides another _(metaprogramming) environment that is still maturing. Or you could say that it's the implicit meaning of meta-objects: what the user can't control about meta-objects in systems which do not allow Tunes-level (system-wide) reflection.

Examples:
<ul>
<li>_(CLOS) has its _(CLOS MOP).
<li>list several research MOP's for Java/C++/etc.
<li>The <a href="http://introspector.sf.net">introspector project</a> for a standard attempt to extract meta-data out of software.
</ul>
