An in-memory storage manager represents XML-compliant documents as a collection of objects in memory. A controller pre-assigns the displays according to control commands from a tactile input device prior to establishing the communication connections with the remote telepresence video conference facilities. The first derivative after an increment of the analytical small variable value is multiplied by the analytical small variable value, a physical value at the reference variable value is added, and a result is output as a physical value after an increment of the analytical small variable value.