>(personally, I'd consider "is to:" as being a lot nearer "MUST" than
>"MAY" - so it does make quite a difference to the way I perceive what
>this point is saying (feel free to tell me why I'm wrong though))
No, it must be either a MUST or a MAY or a SHOULD. The whole point
of using this language form is to avoid the ambiguities of constructs like
"is to".
Phill