http://data.europa.eu/2sa/elap/reuse-buy-build Existing IT systems are reused, before deciding upon buying or even building them. Rationale Taxpayers' money can only be spent once. Reusing existing systems is a lot cheaper that buying new systems or even building them. In most cases, the requirements of public administrations are not very specific, and existing systems are sufficient to support the processes. It may seem that the costs of building new IT systems can be acceptable, but the costs of the maintenance and support of these systems are often forgotten and are much higher than the cost related to the initial development. Principle Source Reusability Underlying Principle (4) of the European Interoperability Framework (EIF)