org.omoa This is the root package: If you want to USE omoa start here.  
 org.omoa.classification In the classification package you'll find classes that fetch data from a DataModel and turn them into styles, size or color values.  
 org.omoa.datamodel The datamodel package contains everything that is involved with non-spatial data: DataModel, ModelDimension, import filters et cetera.  
 org.omoa.event Contains event classes that are specific to omoa.  
 org.omoa.framework This is the omoa extension package: Read this if you want to EXTEND omoa.  
 org.omoa.layer Contains the layer implementations. The maps in a MapFrame consist of layers.  
 org.omoa.overlay Not unlike layers overlays can visualize spatial data. The are visualized on top of the map view.  
 org.omoa.projection The projection package contains the map projection classes... it's quite empty since omoa does not support real time projection at the moment.  
 org.omoa.spacemodel Contains the classes that are needed to load, store and process spatial data.  
 org.omoa.symbol Contains the symbolization classes that are use, for example, by the symbol layer. Symbols visualize spatial data.