Let us assume you have a friend and are aware that he is a passionate collector of first editions. Let us further assume one day you spot a rare book in the window of an antique store being offered for sale at a sensational price. What would you do? Presumably, you would let your friend know about it. The functions of Big Data are similar to this situation.
Every transaction with a credit card leaves traces. Up to 200,000 times a day, people whip out a Viseca card and a data record is generated. This record indicates who used the card and where, when and for what amount. These data items are something all customers can examine on their monthly statement.