Modeling is more precise than the natural language. It assumes, however, that the modeler and the reader know and can apply the modeling language. The most used modeling languages are UML (Unified Modeling Language), SysML (System Modeling Language) and BPMN (Business Process Modeling Notation). Modeling languages are very powerful. But not everything can be represented with them. Every now and then, textual descriptions have to be used as a supplement to the models. To apply modeling in practice, specialized requirements modeling tools are usually required.