System development/Center of excellence

Questions

 * What is a Center of excellence?
 * What should be the scope of a Center of Excellence?
 * Should a Center of Excellence be organised around tools? Probably not. Is it better to organise them around business domains?
 * Is communication and project management the responsibility of a Center of Excellence?
 * Which parties should be involved?
 * Should you involve the business? How? Only via Agile projects?
 * According to Alan Trefler (CEO of Pega) the walls between business and IT should be taken down. Business and IT people should work daily in the same team.