Implementing Scale-Dependent Styles in a WMS Server

[Bill Thoen]

I'm starting to build a MapServer WMS server that will provide national 
street layers to my MapServer client but I have some questions about how 
to approach the problem of serving alternate layers designed for 
different scales and same layers with different styles depending on the 
scale. For example, I've got a US Interstates layer that has been 
thinned so that it is appropriate for scales smaller than 1:10,000,000, 
and I've got another one that I'd use at larger scales (but from 
1:10,000,000 to 1:5,000,000 I want to use one style and for scales 
between 1:5,000,000 and 1:1,000,000 I want to use another style on this 
layer). Then I've got some MapInfo seamless road layers that have the 
highest detail that I'd use at the largest scales, but for these too, I 
have three different styles depending on the display scale.

Can a MapServer WMS server support this sort of thing or should I load 
each layer as needed and style it in the WMS client MAP file? I know how 
to do the latter, but it would be much more convenient to make one call 
to a WMS and get all the appropriate layers rendered with the desired 
styles in one LAYER call in my client MAP files. I've read the how-tos 
for WMS client and server, and glanced at the article about SLD's (but 
haven't understood that very well yet) but so far I haven't seen this 
issue addressed specifically.  Does anyone have any suggestions about 
how to do this, or can you point me to any documentation I should read?

TIA,
- Bill Thoen