Satisfying the OpenClosedPrinciple.

In fact, satisfying it is a matter of playing with whole and parts: the parts are closed but the whole is open (parts may be added). The whole is used to access the parts, offering ReferentialTransparency.

Examples of OpenClosed systems are found in object-orientation (base classes and their specializations) as well as in SoftwareConfigurationManagement (elements and versions; families of derived objects), and even to a lesser extent in news (articles are closed but threads are open).?

[The question mark that was added doesn't tell me how to make the previous text clearer or more convincing.]

Note that this is broken in Wiki, even if one naively attempts to preserve it with ThreadMode. -- MarcGirod