DynamicGRanges-class: DynamicGRanges objects
Description
A DynamicGRanges is a virtual subclass of
  MutableGRanges that is implemented against some
  other data source. It implements an optional caching mechanism, under
  the assumption that the data access will generally be expensive.Subclassing
DynamicGRanges is a virtual class. Subclasses implement the
  actual data access layer by overriding the fetchFromSource
  method, which takes a RangeQuery as its only argument. The
  method is only invoked for regions missing from the cache.