The European Union has published excellent, very practical guidelines to support government agencies purchase software. While it is specifically targeted at purchasing Open Source Software, by its own admission, most of the discussion is valid for purchasing Proprietary Software too. The key message that it describes in business terms, is the importance of using Open Standards in order to adhere to EU purchasing criteria of fair competition, transparency, and long term value for money. The full guide is available here: http://www.osor.eu/studies/expert-guidance/guideline-for-public-administrations-on-procurement-and-open-source-software-2010
