xmlxerces-c

How to get xerces-c to write namespaces with minimum size overhead?

I write an xml file with xerces-c 3.2.1 which looks like

<?xml version="1.0" encoding="UTF-16" standalone="yes" ?>
<Test xmlns="my_namespace" 
      xmlns:xml="http://www.w3.org/XML/1998/namespace" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xsi:schemaLocation="my_namespace myschema.xsd">
        <Elem />
</Test>

with my own default namespace and the xml and xsi namespaces declared.

In my namespace, I have an attribute called dim which needs a namespace declaration, otherwise it would get mixed up with pre-existing xml:dim.

When I set this attribute with elem->setAttributeNS("my_namespace", "myprefix:dim", data); then my xml file looks like

<?xml version="1.0" encoding="UTF-16" standalone="yes" ?>
<Test xmlns="my_namespace" 
      xmlns:xml="http://www.w3.org/XML/1998/namespace" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xsi:schemaLocation="my_namespace myschema.xsd">
         <Elem xmlns:myprefix="my_namespace" myprefix:dim="..."/>
</Test>

with the namespace declaration at each and every element that uses dim attribute I write, which is bad, because for filesize reasons, I would like to have xerces-c writing files like

(the golden one)

<Test xmlns="my_namespace" 
      xmlns:myprefix="my_namespace" 
      xmlns:xml="http://www.w3.org/XML/1998/namespace" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xsi:schemaLocation="my_namespace myschema.xsd">
         <Elem myprefix:dim="..."/>
</Test>

with the namespace prefix declaration just at the root node. But if I add such an entry to the root node using root->setAttributeNS("http://www.w3.org/2000/xmlns/", "xmlns:myprefix", "my_namespace");

then xerces-c produces xml files like

    <Test xmlns="my_namespace" 
      xmlns:myprefix="my_namespace" 
      xmlns:xml="http://www.w3.org/XML/1998/namespace" 
      xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
      xsi:schemaLocation="my_namespace myschema.xsd">
         <myprefix:Elem1 ../>
         <myprefix:Elem2 ../>
         <Elem myprefix:dim="..."/>
</Test>

prefixing all other elements myprefix:elem1, myprefix:elem2, except the one with my dim, which is a pain in the neck...

How can I force xerces-c to my will to write a minimum amount of namespace declarations and prefixes like in the golden one ??

Solution

  • Finally the trick to get the golden one is:

    to add the prefix to the element name (or attribute name) e.g. L"my_prefix:Elem" (additionally to the namespace)

    DOMElement * e4 = doc->createElementNS(defaultNS, (const XMLCh*)L"my_prefix:Elem");
root->appendChild(e4);

    This saves the space in the resulting XML file, but requires more space in the code producing the XML :( and requires even more code as the prefix should not be hardcoded..