Open Babel uses a plugin architecture for file formats, ‘operations’, charge models, forcefields, fingerprints and descriptors. The general idea behind plugins is described on Wikipedia. When you start an application that uses the Open Babel library, it searches for available plugins and loads them. This means, for example, that plugins could be distributed separately to the Open Babel distribution.
In fact, even the plugin types are themselves plugins; this makes it easy to add new categories of plugin. The different types of plugins can be listed using:
C:\>babel -L charges descriptors fingerprints forcefields formats loaders ops
To list the plugins of a particular type, for example, charge models, just specify the plugin type:
C:\>babel -L charges gasteiger Assign Gasteiger-Marsili sigma partial charges mmff94 Assign MMFF94 partial charges qeq Assign QEq (charge equilibration) partial charges (Rappe and Goddard, 199 1) qtpie Assign QTPIE (charge transfer, polarization and equilibration) partial charges (Chen and Martinez, 2007)
To add a new plugin of any type, the general method is very simple:
The following sections describe in depth how to add support for a new file format or operation to Open Babel. Remember that if you do add a new plugin, please contribute the code back to the Open Babel project.