## 1 Introduction  
Recently, with the great popularity and pervasiveness of smart devices (e.g., smart phones or tablet PCs), mobile apps have gradually become a commonplace service in people's daily lives. In addition, with the rapid emerging of information and communication technologies (e.g., mobile and wireless communication, embedded technology, and sensing technology), more and more conventional industries introduce these technologies into their business operation. The tourism and leisure industry is no exception. Famous theme parks such as Walt Disney World, Universal Orlando Resort, and Ocean Park Hong Kong have all introduced information and communication technologies into their park services, which can facilitate visitors' satisfaction, loyalty, revisit intention, etc. Among these theme parks, Walt Disney World is undoubtedly a good example in creating fantastic user experiences based on various technologies such as RFID wristbands (Magic Bands), mobile apps, mobile payment, and even big data analysis [1], which altogether provide considerate services. Although Walt Disney World and other theme parks such as Universal Orlando Resort have improved visitors' experiences with services such as FastPass+ or ExpressSM Pass, we observe that there is still room for improvement. One of the problems is that, in their mobile apps, when tourists need some attraction suggestions, there are a variety of decisions for tourists to make by themselves, which may cause pressure, or so-called choice overload, on tourists and negatively impact tourists'experiences [2; 3]. Moreover, the suggested attractions might include an attraction that the tourist does not want to visit because they are filtered from all attractions in the theme area, not according to the tourist's wish or favorite attraction list only. Another problem is that the suggestion provided by their mobile apps is a list of attractions, often quite lengthy, and the tourists have to browse through the list only to find one attraction they want to visit next. In addition, the literature has investigated the issue of waiting in services and argued that the waiting time is actually important for services in many places such as restaurants and public transportation stations because it may influence the service experience of customers [4; 5; 6; 7]. Although using many fantastic technologies, the problem of long lines in front of the most popular attractions is one of the core problems to be resolved in many theme parks. Walt Disney World, Orlando has tackled this problem with the FastPass+ mechanism, a sorted list of attractions' prompt wait times, and an interactive gaming mobile app for visitors to play during their waiting time in the line. The FastPass+ mechanism is basically a way to reserve an attraction in advance before a visitor goes to take the ride. The sorted indication of attractions' current wait times assists the visitors with their visiting decisions. The interactive gaming mobile app turns visitors' wait times to play times and might help relieve the bad feelings due to long waiting. Among the three solutions, we find that there is still one more thing which can be further improved, namely, the attractions' wait times. The attraction's wait time, called the general waiting time, provided by Walt Disney World is general to all visitors, no matter where the visitors are [8]. That is, the time does not take the tourist's location into account and does not supply visitors with their mobility time information to the attractions based on the visitors' location information. Unfortunately, the Walt Disney World's system only provides general attraction wait times regardless of where the visitors are. Universal Studio's system exhibits the same problem. Many tourism recommendation systems are based on combinatorial optimization challenges. According to the level of complexity and requirements of users' recommended items, different recommendation strategies are applied in tourism recommender systems [9].