SIVA is a web application serving for simulation of the tableau algorithm (TA) for the ALC DL. A user builds a completion tree (to prove the input consistency) step by step, supervised by SIVA. The main goal of SIVA is to teach the DL tableau expansion rules and to visualize the completion tree. The visualization with the tool is simpler and more readable than on a blackboard. One of the main advantages is that beside the completion tree also the tableau is visualized.