Re: protocol: placement of initial/final substrings

[Steven Legg <steven.legg@adacel.com.au>]

Kurt,

Kurt D. Zeilenga wrote:
> At 03:28 PM 12/18/2003, Steven Legg wrote:
>
> > SubstringFilter in [Protocol] is a different ASN.1 type and values of
> > this ASN.1 type are always encoded in BER in the protocol. The BER encoding
> > distinguishes the initial, any and final components with different context
> > specific tags, so the order doesn't matter, and no order is imposed. 
>
>
> I'd argue that there is an ordering has been implicitly imposed
> upon the substrings.  Otherwise *a*b* would be equivalent to *b*a*
> when encoded as BER.

Yes, the ordering of the "any"s matters. I just had a look what X.511 says
about the substrings in a FilterItem. It defers to X.520 and the
SubstringAssertion type (flakey, since it's a different type).
X.520 says:

    "There shall be at most one *initial*, and at most one *final* in *strings*.
     If *initial* is present, it shall be the first element of *strings*. If
     *final* is present, it shall be the last element of *strings*."

Exactly what is meant by *strings* isn't actually defined, but the probable
intent of all this is that the substrings in filter items are meant to be
ordered the same way. A statement to that effect in the protocols draft
would be appropriate.

Regards,
Steven

> Kurt