# the current implementation also changes the username, i.e. it would need an additional parameter,
# I can't support it and I would forbid it anyway.
changeAttributes(ident uid, ident username, string firstName, string lastName) {
  assume exists /account[uid]/admin || uid = username;
 
  assume exists /account[username]; # implicitly true in OO implementations
 
  update /account[username]/firstName firstName;
  update /account[username]/lastName lastName;
}