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Re: ISSUE-15: Null datatype pattern as used by ASN.1 and others

From: Ed Day <edday@obj-sys.com>
Date: Thu, 2 Feb 2006 17:37:30 -0500
Message-ID: <05de01c62849$4564b7b0$4800000a@objsys1>
To: <public-xsd-databinding@w3.org>, <Paul.V.Biron@kp.org>

A NULL is just an empty data type.  It has all kinds of uses.  One trick
that ASN.1 developers do to save a couple of bytes on transmission is to
declare something as NULL OPTIONAL in a sequence instead of BOOLEAN.  That
way, presense (TRUE) costs 2 bytes and absense (FALSE) costs 0, versus 3
bytes either way with a boolean.

As I mentioned in my previous post, it seems there are uses for this in XSD
because many of the schemas I have encountered have an EmptyType of some
sort declared and they do it in different ways.

Regards,

Ed Day


----- Original Message -----
From: <Paul.V.Biron@kp.org>
To: <public-xsd-databinding@w3.org>
Sent: Thursday, February 02, 2006 3:49 PM
Subject: Re: ISSUE-15: Null datatype pattern as used by ASN.1 and others


>
> > There is (apparently) no
> > equivalent in XSD to the ASN.1 NULL type.
>
> Can someone explain ASN.1's NULL type to those of us who haven't done
> ASN.1 for 9 or 10 years?
>
> pvb
>
>
>
Received on Thursday, 2 February 2006 22:36:31 GMT

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