[XML-DEV Mailing List Archive Home] [By Thread] [By Date] [Recent Entries] [Reply To This Message]

Re: Question on Allowing null values iin DTD


dtd empty

> But I want to allow null values for element?

XML does not have null values. It just has character content (#PCDATA)
and nested element content (and attributes). If you are wanting to model
a database entry that may be null, there are several ways that you may
do this, by allowing the element to be empty, or by having an explict
child element, say <null/>, or having an explict attribute, it is your
choice how to model this in teh XML, and you must then code your
application to understand this model. However you chose to model the
null value, the DTD declaration will reflect that model, you can't
declare "null" in a DTD.

> I know that EMPTY element does not allow values. Then what is the purpose of 
> having EMPTY element in DTD? 

To declare elements that do not take eleemnt or character content, such
as the XHTML img or br elements, both <img/> and <br/> are decared
EMPTY. Br often has no attributes either, img should have a src
attribute of course but it is still an empty element.

David

________________________________________________________________________
This e-mail has been scanned for all viruses by Star. The
service is powered by MessageLabs. For more information on a proactive
anti-virus service working around the clock, around the globe, visit:
http://www.star.net.uk
________________________________________________________________________

PURCHASE STYLUS STUDIO ONLINE TODAY!

Purchasing Stylus Studio from our online shop is Easy, Secure and Value Priced!

Buy Stylus Studio Now

Download The World's Best XML IDE!

Accelerate XML development with our award-winning XML IDE - Download a free trial today!

Don't miss another message! Subscribe to this list today.
Email
First Name
Last Name
Company
Subscribe in XML format
RSS 2.0
Atom 0.3
 

Stylus Studio has published XML-DEV in RSS and ATOM formats, enabling users to easily subcribe to the list from their preferred news reader application.


Stylus Studio Sponsored Links are added links designed to provide related and additional information to the visitors of this website. they were not included by the author in the initial post. To view the content without the Sponsor Links please click here.

Site Map | Privacy Policy | Terms of Use | Trademarks
Free Stylus Studio XML Training:
W3C Member
Stylus Studio® and DataDirect XQuery ™are products from DataDirect Technologies, is a registered trademark of Progress Software Corporation, in the U.S. and other countries. © 2004-2013 All Rights Reserved.