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An extensible system is one that enables extensibility. Enabling extensibility means providing non-privileged mechanisms to extend existing objects and to introduce new objects. [[UNIX]] is generally not an extensible system as it does not generally facilitate the hooking of [[system call]]s. For instance, there is no way to hook into the virtual file system. This has motivated the introduction of separate, parallel interfaces by both the GNOME and KDE projects to provide users a more integrated view of their objects.