Towards expressive KR systems integrating datalog and description logics: preliminary report

A chain-and-anchor system stabilizes a standard ladder being used on penetrable or impenetrable surfaces. A chain, secured at either end to one of the ladder rails is held taut by an anchor; at the same time, anti-slip devices prevent ladder from shifting. For use on penetrable surfaces, the anchor and anti-slip devices are penetrating spikes, while for impenetrable surfaces, a weight box is used as an anchor, while anti-skid material fastened to the ladder rail ends serves as anti-slip devices.