A legacy system is an existing application system in operation. While this is an accurate definition, there is a perception that legacy systems is old and antiquated applications operating on mainframe computers. Indeed, Brodie and Stonebraker (Brodie and Stonebreaker Migrating Legacy Systems: Gateway Interfaces and the Incremental Approach, Morgan Kaufmann Publisher Inc., San Francisco, CA, 1995) state that, “a legacy information system is any information system that significantly resists modification and evolution” (p. 3). They define typical legacy systems as: