I am looking for the formal definition of 'perfect information' in game theory.
Please direct me to a book or preferably an online paper where I can find it.
On a related note:
The Wikipedia page for the term is not very useful. It only offers an informal definition:
In game theory, an extensive-form game has perfect information if each player, when making any decision, is perfectly informed of all the events that have previously occurred
Given this definition the simultaneous move examples seem strange. The games mentioned (e.g. iterated prisoner's dilemma) could easily be altered to have sequential moves where the second mover is simply not aware of the first move. This game would have the same extensive form but would no longer fit the informal definition.