Linearly Ordered Plugins through Self-Organization

Nowadays, plugin-based applications are quite common. Eclipse is probably the most popular example of such an application. By means of plugins, end-users can add or remove functionality even at runtime. Besides the kernel, plugin-based applications can be kept very small and nearly everything can be designed as a plugin. However, if plugins are added at runtime, their ordering is difficult to organize. This can be observed for graphical user interface representations of plugins, such as menu or list items for example. In particular, the kernel may not refer to a single concrete plugin, since it has to be independent of concrete plugins-according to the plugin concept. Therefore, self-organization is proposed in the present paper as a solution to structure plugin-based applications. A pattern for linearly ordered plugins is presented. The end-user still retains the possibility to reorder the plugins manually according to his preferences. A sample application of the presented pattern in the context of graphical user interfaces is described.