VSRP, ECMA Standard 367, section 8.3.10, page 32

   Root Procedure rule

   It is valid to specify a name pn as root procedure
   name for a system `S' if and only if it satisfies the
   following conditions:

      1 `pn' is the name of a creation procedure `p' of 
        `S's root type.

      2 `p' has no formal argument.

      3 `p' is precondition-free.