Often known as Branching Time Temporal Logic, CTL allows us to state properties which may be true
on all paths or on some paths in a rooted tree where each branch is a copy of the natural numbers.
For an introduction to temporal logics, see
http://plato.stanford.edu/entries/logic-temporal/
When you enter a formula A, then "closed" means that A is a
theorem because the tableau for ~ A is closed, and "open" means
that it is not a theorem because the tableau for ~ A is open.
When you enter a formula A, then "closed" means that A is a
theorem because the tableau for ~ A is closed, and "open" means
that it is not a theorem because the tableau for ~ A is open.