Dynamics in the use of metasystems in the development of information systems is discussed. An axiomatic level of specification is used to allow dynamic specification of"median" level metasystems which are, in turn, used in information systems specification, analysis and design. Existing metasystems are reviewed and principles for metasystem evaluation are considered The implementation and use of dynamic metasystems in the Plexsys system is overviewed The Plexsys system implements generalized integrity analysis at all levels of logic and mechanisms to insure the mutual integrity of these levels over time.