public void addProperty(String key, Object value) {
            assert(key.indexOf(' ') == -1);
            properties.put(key, value);

            if (value instanceof Item)
                setItemReference((Item)value);
        }
Creates the textual representation for a single Item.
container-search/src/main/java/com/yahoo/prelude/query/textualrepresentation/TextualQueryRepresentation.java