public ApplicationTimeHistogram getLinkApplicationTimeSeriesHistogram() {
        if (direction == LinkDirection.IN_LINK) {
            return getSourceApplicationTimeSeriesHistogramData();
        } else {
            return getTargetApplicationTimeSeriesHistogramData();
        }
    }
A class that describes a relationship between apps in application map

@author netspider
@author emeroad
@author HyunGil Jeong
web/src/main/java/com/navercorp/pinpoint/web/applicationmap/link/Link.java