# Design Principles of a Mixed-Reality Shopping Assistant System in Omnichannel Retail
## 2 Background and Previous Work
### Mixed-Reality Shopping Assistant Systems and Design Principles  
A shopping assistant system which leverages the power of data and analytics to tackle customers' needs is an optimal tool for retailers to compete in omnichannel retail [38]. Moreover, MR-based shopping assistant systems have been suggested for use in omnichannel retail environments to enhance the customer experience [39; 40]. Several studies specifically used optical-see-through MR devices such as MS HoloLens for retail applications to provide utilitarian and hedonic value to the customers. Earlier studies used MS HoloLens to design an in-store recommender system that recognizes the products in stores and displays relevant recommendations [17; 18]. Along with the digital recommendations, the authors highlighted features such as image recognition and immersive digital user interfaces to be used in MR-based shopping assistant systems. Similarly, [PERSON] et al. [39] used the MS HoloLens to develop a system that can identify packaged products in retail environments. [PERSON] et al. [19] developed a shopping assistant application using continuous context awareness and natural interaction techniques (NUI) and integrating digital information in the user interface. These MR applications are developed by extracting requirements from the literature and matching them appropriately by leveraging the capabilities of the device and advancements in the field [18]. Hence, we propose that the general concept of an MR shopping assistant system can be understood as a system where the MR device is used as a medium between the user and retail ecosystem.  
The MR device is used to collect data while also producing output for the user. The back-end computational system device synthesizes real-time data in addition to the data from the retailer to enhance the shopping journey of the user in the form of different shopping assistance elements that can be accessed by the user through the MR device. This concept is depicted in Figure 2.  
These developments further use design theory as the basis to develop prototypes as proofs of concept. In design theory, design principles are considered the foundation that aims to provide a \"systemization of knowledge\" to support industry practitioners and researchers to develop optimal solutions [41; 42]. These principles can also serve as guidelines for developers to support the design of artifacts by describing the standards of a good interactive prototype or system [21]. As supported by [20], standardized tools in the field of MR-based omnichannel retail systems are lacking, and no specific design principles have been found by the authors towards this.  
Hence, the proposed shopping system in this study was built on requirements extracted from prior studies. These findings were combined with feedback from users to propose design principles for future iterations. These principles do not aim to give an exhaustive account of all the required components in the development of an MR shopping assistant system, but present a study that extracts components from the literature and combines them with comments from the users to help future research and development of similar systems. At the core of the system's purpose is to assist customers along their omnichannel shopping journey by providing utilitarian and hedonic value, consequently enhancing their shopping experience.