Object model and data flow. The basic classes of the domain model, highlighted in blue, are common to several genomics applications. A genome browser dataset consists of a list of sequences which define the coordinate system and tracks holding feature data to be plotted against those sequences. Data access (in yellow) is handled by loading contiguous blocks of feature data from an in-process database. An index can quickly determine which blocks intersect with the viewing area. Data flow (blue arrows) proceeds from the database through an LRU (least-recently-used) cache and is presented to TrackRenderers (in green) as tracks and features.