RE: [xml-dev] What is the difference between XSD and DTD

["Michael Kay" <mike@saxonica.com>]

In fact this is another big advantage of XML Schema over DTD. With DTDs, a document is valid if it conforms to any DTD chosen by the document author, which might have been arbitrarily modified to make the document valid. The recipient knows it's valid against some DTD, but they have no idea if it's the right DTD. With XML Schema, the document recipient can specify which schema should be used for validation.

 

Michael Kay

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From: Saha Rabindra N [mailto:saha.rn@mellon.com]
Sent: 27 April 2005 22:39
To: Michael Kay; xml-dev@lists.xml.org
Subject: RE: [xml-dev] What is the difference between XSD and DTD

Hi,

  By "cross validate" I mean :

Lets say Party1 provides an XML document to party2 and before that party1 sends the corresponding XSD document to party2.

Then how does party2 validate the given XML document ? There may be many goofing things, Manual validation does not work for an XML document containing 1000s of records.

Where as, had it been in DTD, the parser would have validated the XML document[say IE browser]. Because DTD is defined in same XML document itself and DTD itself is not a separate doc as opposed to XSD.

 

That's what my understanding is. Can you please correct me ?

 

 

Regards,

RNS

-----Original Message-----
From: Michael Kay [mailto:mike@saxonica.com]
Sent: Wednesday, April 27, 2005 5:27 PM
To: Saha Rabindra N; xml-dev@lists.xml.org
Subject: RE: [xml-dev] What is the difference between XSD and DTD

In terms of validation functionality, XSD can define all the constraints that a DTD can define, and many more. To take a simple example, XSD can say that a particular attribute must be a valid date, or a number, or a list of URIs, or a string that is exactly 8 characters long. To take another example, XSD can define much richer constraints on uniqueness of values within a document.

 

I've no idea what you mean by "cross validate". I believe the only things you can do with a DTD that you can't do with an XML Schema are things that have nothing to do with validation: notably, defining entities.

 

Michael Kay

http://www.saxonica.com/

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From: Saha Rabindra N [mailto:saha.rn@mellon.com]
Sent: 27 April 2005 22:10
To: xml-dev@lists.xml.org
Subject: [xml-dev] What is the difference between XSD and DTD
Importance: High

Hello,

  Can anybody please explain me the real difference between XSD and DTD. Because both are used to define the schema of an XML document.

Whereas DTD is more powerful in the sense that XML parser can cross validate an XML document based on its DTD, and this is really useful in business world as XML is mostly used to exchange the data between parties.

On the other hand XSD defines the schema in XML syntax only which is more readable, but XML parser CAN NOT cross validate one XML document based on a given XSD.

 

Then I am not understanding why people go for XSD ?

 

Can some body correct me please !

Thanks in advance,

 

Regards,

Rabindra Nath Saha

 

 

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