RE: [xml-dev] Re: Designing Schemas for Backward and Forward Compatibil

["Costello, Roger L." <costello@mitre.org>]

Hello Niklas,

I realized yesterday while I was summarizing the discussions that my
initial email was incorrect.  The document I posted yesterday contains
tested and correct examples. 

The approach I was taking in my initial email would create this Relax
NG document (version #3):

<?xml version="1.0" encoding="UTF-8"?>
<element name="BookStore" xmlns="http://relaxng.org/ns/structure/1.0";
         datatypeLibrary="http://www.w3.org/2001/XMLSchema-datatypes";>
    <oneOrMore>
        <element name="Book">
            <element name="Title">
                <text/>
            </element>
            <element name="Author">
                <text/>
            </element>
            <element name="Date">
                <text/>
            </element>
            <element name="ISBN">
                <text/>
            </element>
            <element name="Publisher">
                <text/>
            </element>
            <element name="NumPages"> 
                <data type="nonNegativeInteger"/>
            </element>
            <element name="Hardcover"> 
                <data type="boolean"/>
            </element>
            <zeroOrMore>
                <element>     
                    <anyName/>
                    <text/>
                </element>
            </zeroOrMore>
        </element>
    </oneOrMore>
</element>

Notice that in this schema <NumPages> and <Hardcover> are required
elements.

Now consider a version #1 XML instance document (I'll show only one
<Book> element for brevity):

<BookStore>
    <Book> 
        <Title>My Life and Times</Title>
        <Author>Paul McCartney</Author>
        <Date>1998</Date>
        <ISBN>1-56592-235-2</ISBN>
        <Publisher>McMillin Publishing</Publisher>
    </Book>
</BookStore>

Notice that the <Book> element does not contain <NumPages> or
<Hardcover>

Thus, the version #1 XML instance does not validate against the version
#3 schema, i.e. no backward and forward compatibility.

/Roger

-----Original Message-----
From: news [mailto:news@sea.gmane.org] On Behalf Of Niklas Gustavsson
Sent: Tuesday, August 28, 2007 9:06 AM
To: xml-dev@lists.xml.org
Subject: [xml-dev] Re: Designing Schemas for Backward and Forward
Compatibility - XML Schema, Relax NG, Schematron

Excellent document. I noticed that the RNG example changed from your 
initial email [1] compared to the document below. Specifically, the 
original example used the follow construct for the version 2 schema:

             <element name="Publisher">
                 <text/>
             </element>
             <optional>
                 <element name="Reviewer">
                     <text/>
                 </element>
             </optional>
             <zeroOrMore>
                 <element>
                     <anyName/>
                     <text/>
                 </element>
             </zeroOrMore>

While the example in the document below uses:
     <element name="Publisher">
         <text/>
     </element>
     <optional>
         <element name="NumPages">
             <data type="nonNegativeInteger"/>
         </element>
         <optional>
             <element>
                 <anyName/>
                 <text/>
             </element>
             <zeroOrMore>
                 <element>
                     <anyName/>
                     <text/>
                 </element>
             </zeroOrMore>
         </optional>
     </optional>

I'm assuming there is a reason for this change, but I can't figure out 
what it could be?

[1] http://permalink.gmane.org/gmane.text.xml.devel/36575

/niklas

Costello, Roger L. wrote:
> Hi Folks,
>  
>       I have written a summary of our discussions:
>  
>       http://www.xfront.com/backward-forward-compatibility/
>  
>       Comments welcome.
>  
> /Roger


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