namespace sieve = "urn:ietf:params:xml:ns:sieve"

   start = element sieve:sieve { ( control | action | displayblock |
                                   displaydata | comment | ext )* }

   comment = element sieve:comment { xsd:string }

   ambles =
      (
         ( displaydata | comment | ext )*
      ),
      empty

   preamble = element sieve:preamble { ambles }
   postamble = element sieve:postamble { ambles }

   command =
      (
         attribute name {
           xsd:token {
             pattern = "[A-Za-z_][A-Za-z0-9_]*" } },
         preamble?,
         ( str | num | \list | tag )*,
         test?,
         ( control | action | displayblock)*,
         postamble?
      ),
      empty

   control = element sieve:control { command }
   action = element sieve:action { command }

   test =
      element sieve:test
      {
         attribute name {
           xsd:token {
             pattern = "[A-Za-z_][A-Za-z0-9_]*" } },
         ( str | num | \list | tag | comment | ext )*,
         test*
      }

   \list = element sieve:list { str+ }

   tag = element sieve:tag {
           xsd:token {
             pattern = "[A-Za-z_][A-Za-z0-9_]*" } }

   str = element sieve:str { xsd:string }

   num = element sieve:num { xsd:nonNegativeInteger }

   any = ( element * { any } | attribute * { text } | text )*

   ext = element * - sieve:* { any }*

   displayblock =
      element sieve:displayblock
      {
         ( control | action | displayblock |
           displaydata | comment | ext )*,
         attribute * { text }*
      }

   displaydata = element sieve:displaydata { any* }