private void setNotation(String nname, ExternalIdentifiers ids)
            throws SAXException {
        if (skippedPE) {
            return;
        }

        handler.notationDecl(nname, ids.publicId, ids.systemId, ids.baseUri);
        if (notationInfo.get(nname) == null) {
            notationInfo.put(nname, nname);
        } else {
            // VC: Unique Notation Name
            handler.verror("Duplicate notation name decl: " + nname);
        }
    }
Report a notation declaration, checking for duplicates.
src/nu/validator/gnu/xml/aelfred2/XmlParser.java