When light from an object such as a machine part strikes the camera, the sensitive materials measure the intensity of light and convert the light rays into a range of numbers.
当一个物体上的光，如机器零件，照射到相机上时，敏感材料就可测量出光的强度，把光线转换为一组数字。
2
Without this reference assignment, there would be no way to assign a tests due date to the Machineobject.
如果不分配这个引用，那么就无法将测试到期日期分配给Machine对象。
3
The rule shown in Listing 10 has one conditional element that references a Machineobject.