You can do that today, but a more convenient way will come in the next round of vector editing tools and transforms. It's a common task to want to cut an area at a line, either as part of interactive GIS editing or as part of a transform. We'll have both.
How to do it today? Easy... use the topology overlay Intersect template. Don't even need to use SQL.
Suppose you have a drawing that has a mix of areas and lines. There's a line that crosses an area, like a stream or road that crosses a real estate parcel, and you want the parcel divided into two areas on either side of the line.
1. Create a new area in the drawing where one side of the area follows along the course of the stream and where the rest of the area is bigger than the drawing to be cut. You can use snap to click, click, click remarkably quickly along the course of the stream or road.
2. Select the new area and Ctrl-X to cut it. Paste it into a new, blank drawing. That new drawing is going to be your Overlay drawing.
3. Select the target area in the original drawing so you can use Restrict to Selection to cookie-cut only that one area and not accidentally slice any adjacent areas. Use topology overlay with Intersect to overlay the new area you created as a cookie-cutter over the original area. Done.
You're basically using the boundary of the new area as a cookie cutter to cut along the line that you wanted to use to split the original area into two parts. This technique works fine if you only have a few areas, but obviously it would get tedious if you have many. Also, if the line is intricate along which you want to cut it would be tedious to create the cutting area along the line.. too much zooming in to snap and click.
But, obviously if we can use an area boundary to cookie-cut areas we can use a line. Just a matter of wiring up the templates to make that available in point and click way.
It would also be convenient to have this happen in a generalized way as part of interactive editing, like a Cut With command that uses a given line as a knife to cut an area, etc.