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Re: AW: XML Schema -> DTD?

From: <Noah_Mendelsohn@lotus.com>
Date: Wed, 20 Sep 2000 14:51:10 -0400
To: Michael Hübner <Michael.Huebner@gft-systems.de>
Cc: www-xml-schema-comments@w3.org
Message-ID: <OF669A72AE.AFB44389-ON85256960.0066CFA9@lotus.com>
Sorry, I didn't read your example carefully enough.  Indeed, your original 
challenge includes two differing "locally scoped" definitions for element 
"mytag";  local scoping is a new feature added to schemas.  As mentioned 
in my original response, schemas has many such enhancements which cannot 
in general be modeled in DTDs.    FYI:  local scoping is added because it 
is particularly natural for mapping XML to programming languages and 
databases, and for many simple xml applications.  Consider:

        <BOOK xmlns="somebookvocaburi">
                <TITLE>Moby Dick</TITLE>
                <AUTHOR>
                        <TITLE>Mr.</TITLE>
                        <NAME>Herman Melville</NAME>
                </AUTHOR>
        </BOOK>

The natural type for book title is a string;  author title is probably an 
enumeration {Mr., Ms., Mrs.  ... to use the English language forms}. Local 
scoping captures this sort of idiom.

Infosets refer to the XML Information Set recommendation  [1]. These are a 
key foundation for all future XML specifications, and are the abstraction 
that the schemas design uses to represent all XML documents used by the 
design.  Specifically, the document to be validated and the schema 
documents used to represent schemas are both formally treated as infosets. 
 Similarly, the output of the validation is a so-called Post Schema 
Validation infoset, which is an augmented version of the input.  All of 
this is specified quite clearly and formally in the structures 
specification.

------------------------------------------------------------------------
Noah Mendelsohn                                    Voice: 1-617-693-4036
Lotus Development Corp.                            Fax: 1-617-693-8676
One Rogers Street
Cambridge, MA 02142
------------------------------------------------------------------------







Michael Hübner <Michael.Huebner@gft-systems.de>
Sent by: www-xml-schema-comments-request@w3.org
09/20/00 11:39 AM

 
        To:     "'www-xml-schema-comments@w3.org'" <www-xml-schema-comments@w3.org>
        cc:     (bcc: Noah Mendelsohn/CAM/Lotus)
        Subject:        AW: XML Schema -> DTD?

<quotation from="[1]">
Conformance
The XML schema language must:
...
4.define the relationship between schemas and XML DTDs, and their
information sets;
</quotation>

What is the meaning of "information set"? 

> Unless I'm missing something, it so happens that the
> particular schema you give does correspond to a simple DTD, 

The problem in this DTD is the definition of element "myTag":

<!ELEMENT myTag EMPTY>
<!ATTLIST myTag key (IDREF|ID) #REQUIRED>                 <!-- (IDREF|ID) 
not
valid! -->
Received on Wednesday, 20 September 2000 14:54:38 UTC

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