How does WMS interpret the SLD it receives? Does it parse the document and immediately draws the layers defined from top to bottom? Or does it rely on the 'layers' and 'style' parameters you can send along with the 'GetMap' request to specify what it should draw from the SLD document?
I am basing my question on the reference I found here http://docs.geoserver.org/stable/en/user/services/wms/reference.html. As you can see I can send along a comma separated list of layers and styles and I can send an SLD document. Is it valid to send both? What would happen if I only send an SLD document? And what would happen if I send both an SLD document and a comma separated list of layers and styles?