[comp.protocols.iso] ASN.1 question

vera@portia.Stanford.EDU (James Vera) (08/15/89)

Could someone please clear up my confusion on the following ASN.

My compiler tells me that

X ::= SEQUENCE {
	SEQUENCE OF SEQUENCE {INTEGER},
	SEQUENCE OF SEQUENCE {INTEGER}}
is bad.

But,
X ::= SEQUENCE {
	SEQUENCE OF SET {INTEGER},
	SEQUENCE OF SEQUENCE {INTEGER}}
is good.

But,
X ::= SEQUENCE {
	[1] SEQUENCE OF SEQUENCE {INTEGER},
	[2] SEQUENCE OF SEQUENCE {INTEGER}}
is bad.

But,
X ::= SEQUENCE {
	a SEQUENCE OF SEQUENCE {INTEGER},
	b SEQUENCE OF SEQUENCE {INTEGER}}
is good.



Is my compiler confused or does this make sense to someone?
-- 
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khiem@hpindda.HP.COM (Khiem Ho) (08/17/89)

>
>X ::= SEQUENCE {
>	SEQUENCE OF SEQUENCE {INTEGER},
>	SEQUENCE OF SEQUENCE {INTEGER}}
>is bad.
>.........
>But,
>X ::= SEQUENCE {
>	a SEQUENCE OF SEQUENCE {INTEGER},
>	b SEQUENCE OF SEQUENCE {INTEGER}}
>is good.
>

At the first glance, there seems to be something wrong with
your compiler: those two above should be the same. a, b are
just optional identifiers, and it shouldn't make any difference
whether they are present or not.

Khiem
khiem@hpinddm.HP.COM

vera@portia.Stanford.EDU (James Vera) (08/18/89)

In article <5560033@hpindda.HP.COM> khiem@hpindda.HP.COM (Khiem Ho) writes:
>At the first glance, there seems to be something wrong with
>your compiler: those two above should be the same. a, b are
>just optional identifiers, and it shouldn't make any difference
>whether they are present or not.

Well, actually identifiers are sometimes necessary in order to avoid
ambiguity in the value syntax.  For instance, in

X ::= SET {
	a [0] INTEGER,
	b [1] INTEGER}

the identifiers are necessary in order to distinguish {a 5, b 4} from
{b 5, a 4} [I think that's value syntax].

Still, in my case it appears to me that the compiler is alternately
trying to distinguish the value syntax or the presentation syntax
which makes no sense to me.




-- 
James S. Vera      |         Internet	       |Standard Disclaimers
Stanford University| vera@portia.stanford.edu  |Blah Blah Blah Blah
Bellcore           |vera2@rigel.cc.bellcore.com|vvv My Cutesy Quote vvv
"When I was young it seemed that life was so wonderful..." - Supertramp

lubich@ethz.UUCP (Hannes Lubich) (08/18/89)

James, at least the ISODE-5.0 ASN.1 Compiler does not complain about it.
What compiler have you been using anyway?
Regards
	--HaL

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iso@NIC.DDN.MIL (08/20/89)

>Organization: ETH Zuerich, Switzerland
James, at least the ISODE-5.0 ASN.1 Compiler does not complain about it.
What compiler have you been using anyway?
Regards
       --HaL
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