 The use of large software systems, such as SCADA, is taking place all around the world and computer systems constitute the core of many infrastructures.The society relies greatly on infrastructure such as water, energy, communication and transportation, which again all rely on fully functionally working computer systems.There are several well known examples of when critical systems fail due to bugs or errors in software, such as "when shortage of computer memory caused LAX computers to crash and hundreds of flights to be delayed" (April 30, 2014).