Hi,
I think the asn1 list might find the following discussion interesting.
It occurred on XML Common Biometric Format discussion list (xcbf).
XCBF describes its messages in ASN.1, and encodes them in the XML
Encoding Rules of ASN.1 (XER).
Bancroft
---------- Forwarded message ----------
Date: Sun, 28 Jul 2002 12:47:21 +0100
From: John Larmouth <[EMAIL PROTECTED]>
To: Phil Griffin <[EMAIL PROTECTED]>
Cc: xcbf <[EMAIL PROTECTED]>
Subject: [xcbf] Re: Biometrics web service
Phil Griffin wrote:
>
> John,
>
> Looking at a proposed ASN.1 based WSDL web service for
> biometrics for an X9.84 meeting next week in California
> and I have a question. Isn't
>
> <xsd:complexType name="PrivacyHTTPResponseType">
> <xsd:sequence>
> <xsd:element
> name="privacyObjectResponse" type="xsd:string"/>
> </xsd:sequence>
> </xsd:complexType>
>
> the same thing as saying something like
>
> PrivacyHTTPResponseType ::= SEQUENCE {
> privacyObjectResponse UTF8String
> }
>
> Seems that it would be. It's just hard to imagine why
> anyone would want to use the former instead of the
> later. Maybe it's what I'm used to seeing, but the
> later would seem to be arguably easier to read, write,
> and comprehend.
Yup. This is the thrust of most of my ASN.1/XSD comparisons (see my
LineItemPair in the MoU presentation). The bit I like in the XSD is the
word "complexType"!
> Maybe I've overlooked something. I recall your mentioning
> something during a break in Baltimore at the MoU MG meeting
> last week about the ability to carry all of the UTF8
> characters in XML that are allowed in ASN.1 encodings. Do
> you recall this discussion?
This is a very techie issue. XML forbids (if you believe in the letter
of the W3C law) the transmission of control characters except for a very
few such as CR and LF and TAB and SP. You cannot even (legally) use the
&hex; notation to represent them. This is forbidden.
ASN.1 allows you to write, for example, <bel/>, or <stx/>, and can
transfer a pure binary string (such as an authenticator) in this way.
**** XSD is incapable of transmitting full UNICODE | ISO 10646, because
XML is incapable of representing control characters (without additional
specification such as the ASN.1 spec). ****
Alessandro tells me this has been aired in the XML discussion groups,
and will NOT be mended - they think an XML document should be pure
human-readable graphics characters.
Of course, you can always use a BASE64 encoding for pure binary to
represent a character string, but that is a hell of a lot less efficient
than the ASN.1 transfer with straight Unicode and the <bel/> etc tags
for the occasional control character.
John L
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