This function returns 1 (True) if the attribute attr for the element specified by tagname is declared as a #CONREF attribute in the DTD for the specified document. If the document type definition for your document instance includes the NAMECASE GENERAL NO setting, then the tagname parameter will be case sensitive. (If you have applied an alias map to the document, tagname and attr can be either aliases or real names.)

The doc argument specifies the identifier of the document tree. If omitted or 0, the current document is used.