private boolean canAddComponent(XSObject component, XSDDescription desc) {
        desc.setNamespace(component.getNamespace());

        final SchemaGrammar sg = findGrammar(desc, false);
        if (sg == null) {
            return true;
        }
        else if (sg.isImmutable()) {
            return false;
        }

        short componentType = component.getType();
        final String name = component.getName();

        switch (componentType) {
        case XSConstants.TYPE_DEFINITION :
            if (sg.getGlobalTypeDecl(name) == component) {
                return true;
            }
            break;
        case XSConstants.ATTRIBUTE_DECLARATION :
            if (sg.getGlobalAttributeDecl(name) == component) {
                return true;
            }
            break;
        case XSConstants.ATTRIBUTE_GROUP :
            if (sg.getGlobalAttributeDecl(name) == component) {
                return true;
            }
            break;
        case XSConstants.ELEMENT_DECLARATION :
            if (sg.getGlobalElementDecl(name) == component) {
                return true;
            }
            break;
        case XSConstants.MODEL_GROUP_DEFINITION :
            if (sg.getGlobalGroupDecl(name) == component) {
                return true;
            }
            break;
        case XSConstants.NOTATION_DECLARATION :
            if (sg.getGlobalNotationDecl(name) == component) {
                return true;
            }
            break;
        case XSConstants.IDENTITY_CONSTRAINT :
        case XSConstants.ATTRIBUTE_USE :
        default :
            return true;
        }
        return false;
    }