active updating

In computer programming, suppose we have a data item A whose value depends on data item B, i.e., the value of A must be changed after the value of B changes and before the value of A becomes necessary. Active updating is updating A immediately after B changes, while passive updating or lazy updating (lazy evaluation) is updating A immediately before its value is fetched. And example of this distinction is, e.g., in the implementation of GUI applications: the list of submenu items may depend on the state of the application; this list may be updated either as soon as the state of the application changes ("active") or only when the menu is invoked ("passive").[http://www.drdobbs.com/active-scripting-newsletter-issue-58-/184405884 Active Scripting Newsletter - Issue #58 - November 2004], Dr. Dobb's

Another example is update a visual display as soon as the underlying data change as opposed to clicking the "redraw" button. In this situation active update may create a problem to deal with: an abrupt change of some part of the display may coincide in time with the saccadic movement of the eye, and the change may go unnoticed by a human observer.in: Human Aspects of Visualization: Second IFIP WG 13.7 Workshop on Human-Computer Interaction and Visualization, HCIV (INTERACT) 2009, Uppsala, Sweden, August 24, 2009, [https://books.google.com/books?id=ZuZ5drqoLGgC&pg=PA49 p. 49]

See also direct updating vs. deferred updating in transaction processing.[http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.466.1411&rep=rep1&type=pdf C++ Move Semantics for Exception Safety and Optimization in Software Transactional Memory Libraries], In book: Proceedings of the Third International Workshop on Implementation, Compilation, Optimization of Object-Oriented Languages, Programs and Systems (ICOOOLPS), 2008