It is common to hear of massive IT failures; projects that are over budget, late, poorly aligned to business needs, or all of the above. Often, the resulting losses are in the hundreds of millions of dollars. The cause is almost always the same: uncontrolled complexity. The solution to complexity is simple — or more specifically, simplicity.  This talk is about the mathematical models of complexity and the methodologies needed to control it. Complexity is the most insidious problem facing IT architects. Control it, or it will bury you! David Solivan interviews Roger Sessions about his book 'Simple Architectures for Complex Enterprises'.