Abstract
The BtoB (Business to Business) product means the machine tools, the medical instruments and the other instruments for professional use that are delivered to factories, hospitals and other facilities. Because the user uses it for occupation, the context of use is confined or restricted. If we would like to design the GUI with good usability logically, we have to specify the context of use. Therefore, we propose the method to clarify the context of use for the BtoB product.