CTX_DBBase - Base class for database contexts

The base class for database contexts provides some basic functionality for data base context classes. In particular, the class provides most of the default event handlers that can be overloaded in specific context classes. Overloaded handlers need not to call the default handlers since nothing is done in the default handlers. Handlers for database events are usually called within internal transactions. Thus, all modifications made by the event handler are reset when the transaction fails.

For a number of database operations Not-events are generated that are called in case of an error. An error could be a database (consistency) error but the process event (before event) could have denied the operation as well.