The top is screwed to the base through some oak triangles, which are attached to the top part of the legs and rails, through a larger hole than the screw and using a washer between it and the surface of the triangle. The triangles also stiffen the base. The glue used was extramite which should :!: stop the movement at the joint sides of the top but it may move along the outer edge, time will tell.
Hope that makes sense