||Environment of time consuming read-only methods - methods, which don't modify data,
but it is expected that they will take more time to perform.
||An extension of
DFEnvironmentRO class which provides environment for read-only
||Provides call backs for displaying progress and information as processes run in the DIF
||A lock that can be used to restrict access to a DIF object.
||Most of DIF write method (methods which modifies data or model somehow) use locking.
||Any extension module can install own version of DFEnvironmentRX factory.