Cory Horner wrote:
> ClassificationFunction.evaluate(featureCollection) --> Classification
> (actually i'd rather call this a classifier)
> + parameter specifying things like number of classes, attribute name
>
Expression like: "discrete( SPEED, 5)"
> SlotFunction evaluate(feature) --> slot #
> + parameters like Classification
>
Expression like: "slot( SPEED, {0} )", where {0} is a literal evaluated
above
- slot function needs an Expression (so it can suck out a value to classify)
- with Justin's change the slot in a String context could be the slot
name, in an Interger context the bin number etc...
> In line with the change from org.geotools.filter.Expression to
> org.opengis.filter.expression.Expression
> and org.geotools.filter.FunctionExpression to
> org.opengis.filter.expression.Function
>
> I will do a quick scour of the net to see if there are any standard
> naming for such classification functions, for the day that we support an
> expression like "Slot(EqualInterval(5, SPEED, ROADS))".
>
Correction: "slot( SPEED, EqualInterval( ../*/SPEED, 5 ));
- changed to be evaluated in a pure feature context, ../* used to
indicate feature collection
- two passes needed to process an SLD constructed in this manner (once
pass for feature collection and a second for feature)
> Ian: GeoVista is likely the only other project with a vested interest in
> this... what are you currently using/expect to see?
>
They tend to have functions that use a classification to index out a
color; often using two classifications from different attributes for
interesting visualizations. You change would allow them to be more
explicit and perhaps clean up there code?
> If anyone has any comments or would like to freak out, please do so now.
>
Thanks Cory, this is exactly the kind of trouble that prevented the FM
branch from being a success. Feature.getParent() was a mistake from the
moment it was made (for a feature can be in more then one feature
collection).
Jody
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