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## 4.1.1  A  Clarifying  Example

et us now informally see the intended meaning of the terms of the language TL-F  for the formal details see ection . . oncept expressions are interpreted over pairs of temporal intervals and individuals maning that the individual is in the extension of the concpt at the interval . If a concept is intended to describe an action, then its interpretation can be seen as the set of individual actions of that type occurring at some interval.

ithin a concept expression, the special " variable denotes the current interval of evaluation in the case of actions, it is thought that it refers to the temporal interval at which the action itself occurs. The temporal existential  uantifier introduces interval variables, related to each other and possibly to the variable in a way defined by the set of t emporal constraints.  To evaluate a concept at an interval    , di  erent from the current one, it is necessary to temporally ualify it at written in this way, every occurrence of 