## 1 Introduction
### Guidelines and Standards for Accessibility  
In response, there are various standards and documents published to deliver guidelines for accessible products, albeit with three major limitations. First, the coverage of target users is insufficient in some documents. The United States government has published the Americans with Disabilities Act (hereafter, ADA), including ADA standards [8] for accessible design with recommended numbers and measures so that manufacturers and designers can utilize them as design reference. Although the ADA standard provides design guidelines for various home appliances such as refrigerators, ovens, cooktops, washers, and dryers, its main target user is the wheelchaired population, disregarding the remaining disability groups and elderlies. On the other hand, IEC 63008 [9] provides design guidelines for operable parts such as doors, lids, drawers, and controls for users with various types of impairments, whereas the ADA focuses on the home appliance as a whole product for the specific disabled population. IEC 63008 certainly considered multiple user groups with various impairments and stated that such impairments become more severe as a user ages; however, elderly users are not included as a target user that may encounter different contexts of use. Most ISO documents related to the accessibility, other than ISO 22411 [10] and ISO 9241-20 [11], also omitted elderly users. Another limitation of such documents is the target domains of the application. Despite the wide coverage of disability types, many ISO documents such as ISO 9241-20, ISO TR 29138-1, and ISO TS 16071 [11; 12; 13] mostly focused on the context of software or web accessibility issues. It can be challenging for manufacturers to directly apply the given user needs from the standards into their physical product development. This is because the user behaviors for Graphical User Interfaces (GUIs), such as web or software activities, which are mostly cognitive with minimal physical tasks, can differ from the user interactions for a product with Physical User Interfaces (PUIs). In terms of physical designs, the ADA standard may fall into this category since it provides some physical design guidelines for home appliances as stated earlier. However, the ADA standard preferably provides guidelines mostly for environmental designs rather than for product designs since it is especially targeted for the mobility of wheelchair users; the design guidelines for home appliances are minimal and obscure. IEC 63008 is also a physical design guideline; however, it is insufficient for a designer or manufacturer who designs a whole product since it delivers the guidelines only for the operable parts. Finally, the aforementioned standards and documents are not written in a language easily comprehensible by designers and manufacturers. The designers and manufacturers who are new to the concept of accessibility may not fully utilize or comprehend the contents of these standards due to the lack of detailed explanation on the context of use [14]. The ADA standard provides design guidelines with recommended numbers and measures so that manufacturers and designers can utilize them as design reference. However, ADA's guidelines are obscure or rather minimal as they do not explain how they derived such numeric values. There should be descriptions of a target user's behavior or possible use case scenarios for readers to understand the context of use and implement the values in their designs. Such documents will help manufacturers to logically understand the fact that many potential users encounter such accessibility issues in their ordinary lives; however, the specific needs and frustrations of disabled users when using inaccessible products will only remain unknown, vague, and without empathy. The lack of empathy can breed many misconceptions of disabled users, created by misinterpretation of disabled people's experiences and knowledge [15; 16], since the stakeholders themselves have never experienced what it is like to be a disabled user [17].