possible to classify map layer on JOIN attributes?

[e.zegers@…]

(in this description is my enhancement request and some remarks from Attila 
Csipa from email converstation about this subject)

In my map file I have several shapefile map layers with joins to dbf files.

What I'm trying to do is classify and display such a map layer based on 
attributes from the joined dbf.

But when I try I get an error message:

 msDrawMap(): Image handling error. Failed to draw layer named
'aanleiding'... <brmsDBFGetItemIndex(): DBASE file error. Item
'AANLEIDING' not found. <br>
The item 'AANLEIDING' is a field in the external dbf.

>>Attila Csipa
> I see nothing wrong with your example, but I have not used DBF joins 
> extensively so don't take my word for granted. Also, check which version of 
> Mapserver are you using, IIRC it has been worked on joins in the latest 
> releases and some xbase (dbf) functionality was lost and then later 
> reintroduced around 4.0.

Querying the map does show the joined attributes so I suppose on a map
layer with a join you can query the joined attributes but you cannot use
them to classify and display the layer.
Is this correct? If not, what am I missing and if so, wouldn't this be a
nice enhancement?

>>Attila Csipa
> That is correct. I have personally suggested that enhancement as well but at 
> is turns out it is not easy to implement so it will have to wait until 
> somebody invests the time and effort.

Part of the map file and template can be found at the end of this message.


*****


Map file:

LAYER
  NAME "aanleiding"
  METADATA
    wms_title "aanleiding"
  END
  STATUS ON
  TYPE POLYGON
  DATA bis_rapv
  TOLERANCE 8
  LABELITEM rap_code

  CLASS
    NAME "BIS Aanleiding"
    COLOR 0 255 0
    OUTLINECOLOR 255 0 0
    TEMPLATE "C:\websites\dbf_join\bis_aanleiding.htm"
  END

  JOIN
    TABLE "AANLEIDI.DBF"
    TO "RAP_CODE"
    NAME "bis_aanleiding_join"
    FROM "rap_code"
  END

END

Template file:

<p class="red">
rapportcode: [rap_code]
<br>
</p>
<p>
rapportcode: [bis_aanleiding_join_RAP_CODE]
<br>
aanleiding: [bis_aanleiding_join_AANLEIDING]
<br>
</p>
<p class="red">
XCOORD: [XCOORD]
<br>
YCOORD: [YCOORD]
<br>
</p>

[sdlime]

Never seems to be high enough priority to actually do anything about it. Moving forward for posterity... -Steve