Reference for “XML Protocol Abstract Model”

@TechReport{Williams:03:XPA,
  author      = "Stuart Williams and Mark Jones",
  title       = "{XML} Protocol Abstract Model",
  month       = feb,
  note        = "http://www.w3.org/TR/2003/WD-xmlp-am-20030220/",
  year        = "2003",
  bibsource   = "http://w2.syronex.com/jmr/w3c-biblio",
  type        = "{W3C} Working Draft",
  institution = "W3C",
}