[UMN_MA PSERVER-USERS] Mutiple "DATA " lines in a single l ayer?

[Jeff Dege]

> -----Original Message-----
> From: Stephen Woodbridge [mailto:woodbri at swoodbridge.com] 
> Sent: Friday, May 18, 2007 4:07 PM
> To: Jeff Dege
> Cc: MAPSERVER-USERS at LISTS.UMN.EDU
> Subject: Re: [UMN_MAPSERVER-USERS] RE : [UMN_MA 
> PSERVER-USERS] Mutiple "DATA " lines in a single l ayer?
> 
> Jeff Dege wrote:
> > 
> >  
> > I've never looked at the  MapServer source, but I'm wondering if 
> > allowing DATA statements to be placed in CLASS sections would be a 
> > reasonable enhancement.
> 
> LAYERs are inherently designed to define data sources and as a
container 
> for processing that data source.

Right.  And in this case, the various data statements refer to the same
data source, simply with resolution-specific on-the-fly processing
during data retrieval.
 
> CLASSes allow you to render features of the data source in different 
> ways. Think of a CLASS as like a case statement, Only the first one
that 
> is executed is processed for any given feature.

What we'd be trying to do is to match the resolution of the data we've
requested to the scale we're drawing at.  Which strikes me as being
logically not much different that matching the width of the symbology to
the scale we're drawing at.  But this particular scale-specific
optimization has to happen in the DATA statement, which means multiple
classes each with its own MINSCALE and MAXSCALE, instead of multiple
classes inside the same LAYER.

I know how to do it with multiple layers, but I don't know how to make
sure that future maintainers make their changes consistently to all the
different layers in the mapfile.