Abstract: A method, system and data structures for software development and execution includes a Run Time Event Manager and a set of Models. A Model is a type of data structure that contains no code but an ordered set of references to other Models, to Methods, or other Objects. Models are made accessible to the Run Time Event Manager by registering them upon satisfaction of a set of conditions. In one embodiment of the invention, the Run Time Events Manager is a fetch-execute loop implemented in code that, upon each loop, operates upon one of a set of Models, checks external I/O conditions and, subject to such conditions, may process different or Variant Models, rather than standard or Paradigm Models associated with default conditions. Also, an Elastic Database may be implemented according to the invention that permits dynamically extensible database functionality.