Currently when layouts and sequences are defined in the CSS the @import (at_sdl.css); is required. One down side of this is the that whenever the CSS is altered, even if its nothing to do with the layouts, the ps and pl files are rewritten because there "could be" a change and there is a time delay before composition starts because it is rewriting these files, sometimes for no reason.
Once layouts are written there tend to be limited changes, whereas the CSS for the composition of text elements etc could continue to be tweaked for many years.
What would help is the following: In the main CSS we have an @import url(layout.css); and another file at the job level called layout.css has the @import url(at_sdl,css); instead of the current "bundle" CSS file. Then the Perl script that creates the ps and pl specs could look at the time stamp of the layout.css file instead of the bundle.css file. This would speed composition up enormously.
Just a thought!