What is Public History?

What are some considerations when viewing public history exhibits? What Prof. Jordanova's essay said to me was that first you have to think about what is public history.  Museums and such, obviously qualify, but I never thought of historical fiction as public history.  But it's true, and actually, a little worrisome.  Tying back to the Alamo exhibit, The Alamo with John Wayne would be many people's only knowledge of the Alamo.  These people now believe in a history taught to them through a for-profit, highly glamorized, if not fictionalized movie.  Beyond that, even museums or other things that one would think of as actual history, have some motive behind their production.  The problem arises when that motive interferes with a non-biased portrayal of the issue in question.  As Jordanova pointed out, a major drive with public history is to both place blame, and to educate so that mistakes are not repeated.  An admirable goal.  In every class I have ever taken that dealt with World War 1, I have been told a similar, but still different reason for it beginning.  Historians do not agree.  If they did, there would be far fewer, because no one could publish a new book.  So how are exhibits to keep the past from being repeated, if we can't agree on what the past is?