## 2 Theoretical Background
### S-D Logic in Economic Value for Service Innovation  
[PERSON] and [PERSON] [10] reported that all economic behaviors should be regarded as services and proposed the service-dominant logic (S-D logic) centered on services. The concept states that service is the basis of all economic transactions and value is created through the application of resources to practices that are formed by co-creation [11]. Service-dominant logic emphasizes that, in the transaction process, the specific commodity is only a vehicle for providing the service, so the service provider cannot directly produce value. The benefits of service provision are the experience and solution in the service process, that is, its value is formed by the co-creation of the service providers and the receivers. Consequently, the service receiver, usually considered as the customers, is regarded as a co-creator of value. Service design is increasingly considered an intentional channel to service innovation as it integrates a service perspective with a design approach [12; 13; 14] and is not just a simple design method. The relationships between service design and service innovation seem to be fundamentally overlapped within the service system. The view of service-dominant logic is that the true value of services is generated by value-in-use or value-in-context, rather than value-in-exchange [15]. Therefore, the service receivers are regarded as key members in the value-creation process, which allows service providers to provide innovative service experiences with different thinking and perspectives. [PERSON] and [PERSON]'s [15] latest update to the S-D logic perspective of value co-creation states that direct and indirect interactions occur among all the actors, such as suppliers, third parties, and customers within the service ecosystem. Furthermore, value propositions are co-produced through purposeful collaboration; value is created only when the customer is using the solution provided by the supplier in a specific context [15]. Within the service-dominant logic concept, service receivers are one of the intangible resources of service providers: the perceptions provided by users based on their own needs, cognitions, expectations, or experiences play an important role in the value-creation process. The value proposition in the service process is provided by the service provider and evaluated by the service receivers. Service innovation can be classified through the value theory of S-D logic based on two dimensions: the degree of value co-creation and the degree of network collaboration. Four types of service innovation have been proposed: (1) traditional innovation, with a focus on product-based innovation through improving quality and reducing costs, (2) collaborative innovation, with a focus on process-oriented innovation, through outsourcing relationships with other organizations and establishing cooperative relationships, (3) customer-oriented innovation, which focuses on strengthening the interactions between enterprises and customers, or between customers and customers through the network model and (4) service-oriented innovation, with a focus on maximizing the value of the service economy, which is the highest degree of value co-creation and network collaboration [16]. This concept emphasizes that customers are value co-creators, and the joint participation of enterprises and customers is an important aspect for value co-creation in the service industry [17]. Furthermore, collaboration includes all internal and external actors that are connected to each other in all service networks [18]. The concept of open innovation, i.e., IOI-based systematic innovation, states that internal and external ideas are combined in systems whose requirements are defined by a business model [19]. Open innovation is a model that allows for a two-way flow of knowledge from inside the firm out (outbound) and from outside in (inbound) [20].