* @return a bitset with all specified versions set
     */
    public BitSet convertVersions( String spec )
    {
        BitSet set = new BitSet();
        if ( spec.toLowerCase().equals("all") )
        {
            for ( int i=1;i<=versions.size();i++ )
                set.set(i);
        }
        else
        {
            HashMap<String,Short> map = new HashMap<String,Short>();
            for ( int i=0;i<versions.size();i++ )
            {
                Version v = versions.get( i );
                String vid = v.versionID(groups);
                map.put( vid, (short)(i+1) );
            }
            StringTokenizer st = new StringTokenizer(spec,",");
            while ( st.hasMoreTokens() )
            {
                String token = st.nextToken();
                if ( map.containsKey(token) )
                    set.set( map.get(token).shortValue() );
                else
                    System.out.println("couldn't find version "+token
                        +" (ignored)");
            }
        }
        return set;
    }