What does Namespace URI Constant.NamespaceSpecNS mean?

I am porting parts of a Java project to C # and came across this constant Constant.NamespaceSpecNS.

One of its uses is in the following Java context:

_xmlElement.setAttributeNS(Constants.NamespaceSpecNS,"a_qualified_name", "some_value");

      

        
        
        
      

    

where is seAttributesNS

declared in org.w3c.dom Interface Element

.

So, from this call, I know that this is a kind of uri namespace, but that's about all I know. Can anyone point out where this one is Constant.NamespaceSpecNS

defined? What is the meaning?