# Smart Warehouses: Rationale, Challenges and Solution Directions
## 4 Results
### RQ-1: What Warehouse Sub-Domains Adopted the Smart Warehouse Technology?  
The total management of a warehouse consists of many sub-domains. The most important sub-domains from the literature that have adopted smart warehouse technology are presented in Figure 3. The most important sub-domains are warehouse operations and management, which are two key factors in which different operations are summed. The different sub-domains are explained in detail in the chapter.  
Nowadays, technology is well-embedded in all warehouses. Due to complex and high varied customer orders, reduced inventory, and the demand for real-time information, the traditional (manual) warehouse operations are no longer adequate in Industry 4.0 [3; 13; 22; 27; 28; 30; 32]. Modern warehouse management processes are guided by database-driven software applications such as inventory management system (IMS) [26], advance planning and scheduling (APS), transport management system (TMS), warehouse management system (WMS), and enterprise resource planning (ERP) [29]. The most common domain where smart warehouse technology is adopted would be the WMS [24]. The time the products are within the warehouse is called a warehouses' life cycle, this cycle is managed by the WMS and consists of order receiving, storing, picking, and shipping [14; 23; 27; 28]. [PERSON] et al. [21] take WMS a broader perspective by stating that warehouse management consists of the following subdomains: warehouse-entry management, shelves management, warehouse-out management, and storage management.  
Various technologies have been adopted in warehouses to improve performance: radio-frequency identification (RFID) is seen as the most promising. RFID addresses the two key demands when it comes to improving WMSs: higher efficiency and lower costs [16]. Furthermore, RFID allows for automatic identification and enables real-time data [17]. Other advantages of RFID technology are its (small) size, variety in shapes, reusability, relatively low cost, accuracy, and its ability to be read wireless [16].  
As the products have numerous amounts of interactions during this process, focusing on the improvement of core functions makes warehouse management more efficient [32]. The functions to optimize a warehouse are product allocation, product picking, and product identification [23]. As part of smart warehouse automation, many 'online retailers have changed their warehouse pick-and-pack operations from human-to-goods to goods-to-human' [20]. Current Internet of things (IoT)-based tracking technologies, such as RFID, allow systems to cope with complex randomness [25; 30]. Such randomness is the allocation of products to different slots of shelves while maximizing space occupation and minimizing handling costs [18; 23]. For transportation, automated guided vehicles (AGV) are introduced  
Figure 3: Summary of frequency of sub-domains.  
to enhance operations and efficiency [20]. The AGVs are supported by an order-picking operations system (OPOS), which guides the order-picking and batch-handling [19]. As \"mechanical, physical, electrical, and software components cannot be isolated and do not function independently\" [15], the various components are coined in cyber-physical systems (CPS). These CPSs require to be protected through cybersecurity when transitioning towards Industry 4.0 [31].