What is a presidential library, and will Trump build his own ?

After years of construction, almost a billion dollars in costs and controversy over the design, the Obama Presidential Library is set to open in just a few weeks’ time in Chicago. Never to be outdone by his longtime Democratic rival, Donald Trump is also currently pushing ahead with his own library in Miami, setting up a battle of architectural vanity, legacy and fundraising capacity. But how has the Presidential Library System evolved over the years? Reporter Simon Tierney joined Pat to Explain.