dap4/d4core/src/main/java/dap4/core/util/DapUtil.java
static public String fqnPrefix(String fqn)
    {
        int structindex = fqn.lastIndexOf('.');
        int groupindex = fqn.lastIndexOf('/');
        if(structindex >= 0)
            return fqn.substring(0, structindex);
        else
            return fqn.substring(0, groupindex);
    }
static public String fqnPrefix(String fqn)
    {
        int structindex = fqn.lastIndexOf('.');
        int groupindex = fqn.lastIndexOf('/');
        if(structindex >= 0)
            return fqn.substring(0, structindex);
        else
            return fqn.substring(0, groupindex);
    }
return prefix name part of an fqn; result will be escaped.