dap4/d4core/src/main/java/dap4/core/dmr/DapGroup.java
public DapNode
    findByFQN(String fqn, DapSort... sortset)
            throws DapException
    {
        fqn = fqn.trim();
        if(fqn == null)
            return null;
        if(fqn.charAt(0) != '/') {
            String prefix = this.getFQN();
            fqn = prefix + '/' + fqn;
        }
        return getDataset().lookup(fqn, sortset);
    }
public DapNode
    findByFQN(String fqn, DapSort... sortset)
            throws DapException
    {
        fqn = fqn.trim();
        if(fqn == null)
            return null;
        if(fqn.charAt(0) != '/') {
            String prefix = this.getFQN();
            fqn = prefix + '/' + fqn;
        }
        return getDataset().lookup(fqn, sortset);
    }
Parse an FQN and use it to trace to a specific
object in a dataset. Absolute FQN paths are passed
to DapDataset.findByFQN(). Relative FQNs are assumed
to be WRT to the FQN of this node

@param fqn     the fully qualified name
@param sortset the kinds of object we are looking for
@return the matching Dap Node or null if not found