Creating legends on fly in Mapserver

Question

I've got a spatial table in Oracle and a WMS-T in Mapserver, defined in a layer that query that table. The table has several columns and I pass the column to select as a parameter in OpenLayers, so the layer definition in mapserver is the following:

LAYER
    NAME "layer_example"
    CONNECTION "oracle/user@oracleservice/oracle"
    CONNECTIONTYPE ORACLESPATIAL
    DATA "geom FROM  (SELECT E.%type% as value, E.YEAR as YEAR, E.SHAPE_60M as geom FROM EMISSIONS E
                      WHERE E.level=%level% ) USING NONE"

    TYPE POLYGON

    STATUS OFF
    TRANSPARENCY 100

    VALIDATION
        'level' '^[0-9]$'
        'type'       '^[a-zA-Z0-9]+$' #column name
    END

    PROJECTION
            "init=epsg:4326"
    END
    UNITS METERS
    SIZEUNITS PIXELS
    TOLERANCE 0
    TOLERANCEUNITS PIXELS
    CLASSITEM value
    ### LEGEND DEFINITION HERE ###

    METADATA
            "ows_title" "emissions"
        "ows_srs" "EPSG:3035 EPSG:4326 EPSG:900913"
        "ows_timeformat" "YYYY"
        "ows_timeextent" "2000/2011"
        "ows_timeitem" "YEAR"
            "ows_timedefault" "2000"
        "wms_enable_request" "*"
        "wms_metadataurl_format" "text/xml"
        "wms_metadataurl_type" "ISO19115:2003"

    END
END

The problem is the legend! Since the columns in the table has got different classes of values for their legends, how can I define the legend on fly? I tried to define legends in different files and then INCLUDE "legend_%type%.map", but the variable substitution doesn't work for INCLUDE. Actually, it would be great if Mapserver had this feature.

Anyway, some ideas and suggestions? Hope the question is clear!

Answer 1

I was able to define legend on fly (i.e. definition of boundaries are made on fly) using the following trick:

DATA "geom FROM  (SELECT E.%type% as value, (select max(%type%)/5 from EMISSIONS) as fifth_of_max_value, E.YEAR as YEAR, E.SHAPE_60M as geomFROM EMISSIONS E
        WHERE e.level=%level% ) USING NONE"

Then, in the classes definition, I use the [fifth_of_max_value] value to define thresholds of five classes:

CLASSITEM value
    CLASS
        NAME 'Absent'
        EXPRESSION ([value]==0)
        STYLE
            ANGLE 360
            OUTLINECOLOR 95 95 95
            COLOR 192 255 255
            SYMBOL 0
        END
    END
    CLASS
        NAME 'Moderate'
        EXPRESSION ([value]>0  AND [value]<=[fifth_of_max_value])
        STYLE
            ANGLE 360
            OUTLINECOLOR 95 95 95
            COLOR 0 255 255
            SYMBOL 0
        END
    END
    CLASS
        NAME 'Medium'
        EXPRESSION ([value]>[fifth_of_max_value]  AND [value]<=[fifth_of_max_value]*2)
        STYLE
            ANGLE 360
            OUTLINECOLOR 95 95 95
            COLOR 0 255 0
            SYMBOL 0
        END
    END
    CLASS
        NAME 'Strong'
        EXPRESSION ([value]>[fifth_of_max_value]*2  AND [value]<=[fifth_of_max_value]*3)
        STYLE
            ANGLE 360
            OUTLINECOLOR 95 95 95
            COLOR 255 176 0
            SYMBOL 0
        END
    END
    CLASS
        NAME 'Very strong'
        EXPRESSION ([value]>[fifth_of_max_value]*3  AND [value]<=[fifth_of_max_value]*4)
        STYLE
            ANGLE 360
            OUTLINECOLOR 95 95 95
            COLOR 255 0 0
            SYMBOL 0
        END
    END
    CLASS
        NAME 'Excessive'
        EXPRESSION ([value]>[fifth_of_max_value]*4 AND [value]<=[fifth_of_max_value]*5)
        STYLE
            ANGLE 360
            OUTLINECOLOR 95 95 95
            COLOR 128 0 0
            SYMBOL 0
        END
    END

Thanks.