We have a question on size constraint syntax. In the RANAP specification, the following declaration exists:
TransportLayerAddress ::= BIT STRING (SIZE (1..160), ...)
According to X.680, an extensible size should be written as follows:
(SIZE (1..160,...))
We are wondering how the above definition should be treated. X.680 Annex G gives several examples of extensible situations, but this one does not appear to be covered. It would appear to us that in the case above, the ... is indicating that additional constraints can be added in the future and would not apply to the 1..160 range.
You are correct.
> How should this be
interpreted?
Additional subtype constraints (not only size constraints) can be added, but I'd not recommend such a use ;)
FYI rule <4> on page 268 and rule <5> on page 270 of my book (but I know that it is less authoritative than the standard!) state:
<4> When the SIZE constraint is extensible, a definition such
as T ::= IA5String (SIZE (1|2, ..., 3)) is equivalent to T ::=
IA5String (SIZE (1|2), ..., SIZE (1|2|3)).
<5> When the FROM constraint is extensible, a definition like T ::=
IA5String (FROM ("abc", ..., "de")) is equivalent to T ::= IA5String
(FROM ("abc"), ..., FROM ("abcde")).
--
Olivier DUBUISSON
france telecom R&D
DTL/TAL - 22307 Lannion Cedex - France t: +33 2 96 05 38 50 - f: +33 2 96 05 39 45 - http://asn1.elibel.tm.fr/
