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   Re: [xml-dev] ASN.1 is an XML Schema Language (Fix those lists!) andBina

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Amelia A. Lewis wrote:

>On Sat, 1 Nov 2003 23:16:03 -0500
>"Alessandro Triglia" <sandro@mclink.it> wrote:
>>Rich Salz ha scritto:
>>>I think you misunderstand Simon.  Does ASN.1/X.694 have the 
>>>equivalent of a "text node"?  For example:
>>>	<foo>this is <item>1<item> line of text with
>>>        <item>2</item> numbers in it.</foo>
>>>What about
>>>	<foo>A second line with <item>1<item>, <item>2</item>, no,
>>>        <item>3</item> numbers.</foo>
>>>In XML Schema, those match the same definition of foo.  How 
>>>do you write the equivalent in ASN.1/X.694?
>Please note the question.  The answer doesn't address it.
If you want to write a schema for the above using ASN.1 and X.694, you 
can simply write an XML schema for the element foo and use it with an 
implementation of X.694.

<xs:schema xml:ns="http://www.w3.org/2001/XMLSchema";>
  <xs:element name="foo">
    <xs:complexType mixed="true">
        <xs:element name="item" type="xsd:string" minOccurs="0" 

X.694 implementations will produce an ASN.1 Schema "equivalent" to the 
W3C XML Schema:

  embed-values SEQUENCE OF UTF8String,
  item-list [UNTAGGED] SEQUENCE OF elem UTF8String

EXTENDED-XER encodings of this type will look like the one of the example:

<foo> text  <item> 1234 </item> more

>>ASN.1 supports mixed content in the "Extended XML encoding rules"
>>You can write a type definition such as the following:
>>MyElementTypeWithMixedContent ::= [EMBED-VALUES] SEQUENCE {
>>	embed-values SEQUENCE OF UTF8String,
>>	an-attribute [ATTRIBUTE] INTEGER,
>>	another-attribute [ATTRIBUTE] UTF8String,
>>	a-child-element AnotherElementType,
>>	another-child-element INTEGER
>>[EMBED-VALUES] and [ATTRIBUTE] are examples of "XER encoding
>>The [EMBED-VALUES] encoding instruction assigned to the SEQUENCE type
>>causes the multiple strings of the "embed-values" component (the first
>>component of the SEQUENCE) to provide the text that is interleaved
>>with the child elements (before the first one, between each pair, and
>>after the last one). In this example, there are two (mandatory) child
>>elements ("a-child-element" and "another-child-element"), so there
>>must be exactly three strings(possibly empty) in the SEQUENCE OF
>But that isn't mixed content.  Not in the XML sense.  If I *must* write
><p>String <b>emphasized</b> the end.</p>  But I *want* to write
><p>String <b>some <i>real nonsense</i>, no?</b> Or perhaps
You can write an ASN.1 type for this kind of document:

  embed-values SEQUENCE OF UTF8String,
    p Inline,
    b Inline,
    i Inline } }

Foo ::= Inline

The following XML document is an EXTENDED-XER encoding of Foo:


>Classic document-style mixed content.  Very useful stuff if, for
>instance, you're embedding documentation into a product description. 
>The example provided, if I understand it correctly, cannot support that.
As shown above, you can have EXTENDED-XER encodings with mixed contents.

Michael Marchegay

>ASN.1 as a non-mixed-content schema language for XML that has the
>ability to generate [unparsable, disastrously fragile*] compact binary
>structures has interesting use cases.  An inability to support mixed
>content means it isn't a replacement for DTDs, WXS, or RNG, all of which
>do have that capability.
>* she didn't really say that, did she?


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