@XmlAccessorType(XmlAccessType.NONE)
public class Measurement {
@XmlIDREF
@XmlAttribute(required = true)
private final Metric metric;
<BUG>@XmlElement(required = true)

@XmlElementRef
private final Value value;
</BUG>
public Measurement() {

@XmlAccessorType(XmlAccessType.NONE)
public class Measurement {
@XmlIDREF
@XmlAttribute(required = true)
private final Metric metric;
@XmlAttribute(required = true)
private final String value;
