title: Xml pattern restriction. Pattern for "x.x" like attribute value representing a version number
body: <p>I have an XML attribute representing the version numbering of a file.</p>
  
  <p>The file version is identified internally by two byte fields so that, theoretically the versión could go from: 0.1 to 255.255.</p>
  
  <p>Is there any way to express that as a pattern restriction or any other kind of restriction in an XML Schema?</p>
  
  <p>Note: The problem is not restricting the format to three numbers, a dot and another three numbers. The problem is disallowing values greater than 255...</p>