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

From: <paul.downey@bt.com>
Date: Mon, 30 Jan 2006 13:55:04 -0000
Message-ID: <2A7793353757DB4392DF4DFBBC9522550276F2A3@I2KM11-UKBR.domain1.systemhost.net>
To: <public-xsd-databinding@w3.org>, <edday@obj-sys.com>

Hi Ed,

> But this reminds me of another binding issue.  There is (apparently) no
> equivalent in XSD to the ASN.1 NULL type.  The result is that users have to
> make up their own and the results are often inconsistent.  For example, in
> the CSTA specs, we see the following type definition:

>  <xsd:annotation>
>    <xsd:documentation>replacement for ASN.1 NULL type and helper type for
>    representation of the ASN.1 BIT STRING type</xsd:documentation>
>  </xsd:annotation>
>  <xsd:complexType name="Empty"/>

I notice that ITU-T Rec. X.694 (01/2004) suggests this pattern:
http://www.itu.int/ITU-T/studygroups/com17/languages/X694pdf

> In XMPP, there is:
>
>  <xs:simpleType name='empty'>
>    <xs:restriction base='xs:string'>
>      <xs:enumeration value=''/>
>    </xs:restriction>
>  </xs:simpleType>


> It would be nice if a best practice schema pattern for representing empty
> data could be published.


I suggest we add 'Null datatype" to our roadmap and offer both 
of these as possible Schema patterns currently in the wild.


Paul
Received on Monday, 30 January 2006 13:55:23 GMT

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