DOM Namespace Question

[rchauhan <rc...@micron.com>]

I have a beginners question on using Xerces DOM API to build an XML document that contains namespaces.  Checked the archives and sample and could not find the right answer...


If I want to create a XML document shown below:


<myNS:Root xmlns:myNS="http://www.myNamespace.com">
	<myNS:Child1"/>
	<myNS:Child2/>
</myNS:Root>
   

Is this the right way to implement with Xerces?

DOMImplementation* impl =  DOMImplementationRegistry::getDOMImplementation(X("Core"));
DOMDocument* doc = impl->createDocument(
                    0,                    // root element namespace URI.
                    0,         // root element name
                    0);                   // document type object (DTD).


DOMElement* rootElem = doc->createElementNS(X("http://www.myNamespace.com"), X("myNS:Root"));
doc->appendChild(rootElem);

DOMElement *firstChild = doc->createElementNS(X("http://www.myNamespace.com"), X("myNS:Child1"));
rootElem->appendChild(firstChild);
.................


The questions I have are:

1.  Do I need to provide the Namespace URI for for the Child1 node also?  I assumed the information would be redundant and I don't have to provide it again (can get by with providing an empty namespaceURI).

2.  Has anyone modified DOMPrint to print out the Namespace URI also (output similar to the xml doc shown above)?

3.  What does the setPrefix() method in DOMNode class do?  When would I use it? 

4.  If I want to copy a namespace'd node from one document to another, are there any special considerations I need to look into.



Any help on this questions would be appreciated,

Thanks,

Ravin


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Re: DOM Namespace Question

[Gareth Reakes <ga...@decisionsoft.com>]

Hi,
	namespace attributes affect the uri of elements /attributes at 
parse time only.

> The questions I have are:
> 
> 1.  Do I need to provide the Namespace URI for for the Child1 node also?  I assumed the information would be redundant and I don't have to provide it again (can get by with providing an empty namespaceURI).

Yes, if you set an elements uri it does not cascade.

> 2.  Has anyone modified DOMPrint to print out the Namespace URI also (output similar to the xml doc shown above)?

It does print out the namespace information. The problem is that it does 
not create the appropriate namespace attributes to make the document 
namespace well formed. The normalizeDocument method does this but is not 
implemented as yet. I have the code that does this but I need to implement 
entity replacement and text node consolidation. It may make it into the 
next release.


> 3.  What does the setPrefix() method in DOMNode class do?  When would I use it? 

If it is an element or attribute then it will set the prefix part of the 
QName. ie the bit before the :. This can be used so that the document you 
print out has the desirable prefixes and is namespace well formed.

> 4.  If I want to copy a namespace'd node from one document to another, are there any special considerations I need to look into.

The notion of a namespace node from the infoset does not exist in standard 
DOM (it sort of does in DOM 3 XPath). If you mean the namespace attribute 
then copying it from one document to another will require a standard 
importNode from the document. Bear in mind this will have no effect on the 
uri of any nodes that you place this attribute on.

Gareth


-- 
Gareth Reakes, Head of Product Development  +44-1865-203192
DecisionSoft Limited                        http://www.decisionsoft.com
XML Development and Services





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