Device numbers are used to identify the functions of devices shown on a schematic diagram. With reference to the example in the above diagram. Here is another concrete example, illustrated by a Venn diagram. Extensive use is usually made of a diagrammatic style known as the block diagram. An example of a triangle diagram appears to the right. See the UML class diagram below. Database modeling in Visio revolves around a Database Model Diagram (DMD). Each of the functions in the diagram is explained below. See also the UML class diagram below. These overlays are similar to mathematical Venn diagram overlays. These are shown as lines on a Thermodynamic cycle diagram. An example is given in the adjacent diagram. ESR can be shown as an ohmic part in the above vector diagram. The apparatus is assembled as in the diagram. The pieces start in the position shown in the diagram above.