Paul,

I didn't mean to trivialize the power of the whole facility. Rather, I am
just interested in the encoding of this one isolated construct.

Paul Long
ipDialog, Inc.

> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On Behalf Of Paul
> Thorpe
> Sent: Monday, June 24, 2002 6:42 PM
> To: [EMAIL PROTECTED]
> Subject: RE: [ASN.1] TYPE-IDENTIFIER.&Type
>
>
> Hi Paul,
>
> I will answer your second question.  No, that is not all there is to
> it.  The real benefit of the all of this "&." comes from using table
> constraints (and component relation constraints) rather than just a type
> constraint as shown in your example.  I suggest you refer the book
> "Communications Between Heterogenus Systems" by Oliver Dubuisson, or
> "ASN.1 Complete" by John Larmouth for good explanations of the real power
> of this notation.  Both of these books are downloadable free of charge
> from www.oss.com, or can be purchased from amazon.com.
>
> ------------------------------------------------------------------
> ----------
> Paul E. Thorpe                                 Toll Free    :
> 1-888-OSS-ASN1
> OSS Nokalva                                    International:
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> http://www.oss.com                             Fax          :
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>
> On Mon, 24 Jun 2002, Paul Long wrote:
>
> > Rajul,
> >
> > Okay, thanks. So I think you're answer to my first question is, yes. :-)
> >
> > Also, given X:
> >
> > X ::= SEQUENCE {
> >     a INTEGER, -- stuff...
> >     b BOOLEAN
> > }
> >
> > I believe that Z1:
> >
> > Z1 ::= SEQUENCE {
> >     y TYPE-IDENTIFIER.&Type (X)
> > }
> >
> > encodes in PER exactly like Z2:
> >
> > Z2 ::= SEQUENCE {
> >     y OCTET STRING  -- contains X
> > }
> >
> > True?
> >
> > Paul Long
> > ipDialog, Inc.
> >
> > > -----Original Message-----
> > > From: Rajul Gupta [mailto:[EMAIL PROTECTED]]
> > > Sent: Monday, June 24, 2002 4:13 PM
> > > To: [EMAIL PROTECTED]
> > > Cc: [EMAIL PROTECTED]
> > > Subject: Re: [ASN.1] TYPE-IDENTIFIER.&Type
> > >
> > >
> > > Hi Paul,
> > >
> > > (X) is a type constraints here, and it says that "y" MUST be
> of type "X"
> > > only. Syntactically, this is equivalent to
> > >
> > > Z ::= SEQUENCE {
> > >        y       X
> > > }
> > >
> > > However, this kind of syntax (your syntax) is useful in case
> of PER. PER
> > > always doesn't have length encoded, but while encoding open
> > > types, PER puts
> > > a length wrapper also. So if you are using PER, then at the
> decoding side
> > > you can easily find out the length of encoded open type value, without
> > > knowing it's type.
> > >
> > > Usually this type of construct is useful for security fields.
> Using length
> > > wrapper you can easily find out the length of security data
> and leave this
> > > data unwrapped and unprocessed in your application, and pass
> it to other
> > > application or function, where this security data is used.
> > >
> > > I hope this answer could be helpful for you.
> > >
> > > Rajul
> > >
> > > > I've put it off too long. Now it's time for me learn this
> ".&" stuff. Is
> > > y,
> > > > below, encoded in PER as an open type that contains an
> encoding of X? Is
> > > > that all there is to it?
> > > > Also, what syntactical role does the "(X)" play? Is
> > > > this a constraint and otherwise y could be encoded as an open
> > > type of any
> > > > type?
> > > > X ::= SEQUENCE {
> > > > a INTEGER, -- stuff...
> > > > b BOOLEAN
> > > > }
> > > >
> > > > Z ::= SEQUENCE {
> > > > y TYPE-IDENTIFIER.&Type (X)
> > > > }
> > > >
> > > > Paul Long
> > > > ipDialog, Inc.

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