Source: http://www.univ-bejaia.dz/jspui/bitstream/123456789/8657/1/Etude%20et%20Configuration%20d%27un%20entrep%C3%B4t%20de%20donn%C3%A9es%20cas%20h%C3%B4pital%20Khelil%20Amrane.pdf