public static LinkData copyOf(Application fromApplication, Application toApplication, LinkCallDataMap linkCallDataMap) {
        Objects.requireNonNull(linkCallDataMap, "linkCallDataMap");
        return new LinkData(fromApplication, toApplication, TimeWindowFunction.identity(), linkCallDataMap);
    }
application Out/In relationship stored in DB

@author netspider
@author emeroad
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/rawdata/LinkData.java