## 6 Discussion and Conclusions  
The paper contributes to the literature with an initial model for ZDM that can be adapted primarily for manufacturing but also for process industry companies. The initial model is a further development of the ZDM approach previously outlined in [7; 8], and a step towards implementation in real cases. Further, the initial ZDM model continues to developing ZDM as a concept via a systematic approach with a solid mathematical foundation. Further, the paper contributes to practice by bringing up a number of areas and topics that are preconditions for moving towards the ZDM approach and implementation of a ZDM model. The preconditions are, for instance: (i) monitoring of adequate process parameters; (ii) an ability to use data about the input and provide data to the next or previous step(s) in the value chain; (iii) measure relevant parameters on the input and output and potentially also in the process where relevant, so as to be able to sort out what should not be conveyed to the next step; (iv) monitoring of relevant parameters of production equipment status and function and predictive maintenance for the equipment; and (v) data storage with analytics and visualization of results. All five are needed for the initial ZDM model to render full value. In addition, the managerial contribution of the paper is that the initial ZDM model outlined can be used for: (vi) re-configuration and re-organization of production and (vii) re-scheduling of production. The system model and connected control systems (see Figures 3 and 4) support both the practical and managerial aspects (i-vii). The understanding of a system's behavior (see Figures 1 and 2) is crucial in order to model it. Further, it is of utmost importance to take care of not only what can be explained by data but also the domain knowledge, which may be formal (written/documented) or tacit (embodied in production staff, development engineers, maintenance staff, etc.). Without this, the system model will be less useful and less complete. The initial ZDM model outlined in this paper is a next step and partly a response to what [2; 9; 10; 11] are looking for. The initial ZDM model further develops the ZDM concept and uses state-of-the-art methods concerning, e.g., fault tolerances, predictive maintenance and continuous quality measurement/monitoring, in order to get to the next level of applicability. The previous barriers for ZDM to be successful (see the introduction section) are starting to be overcome by the recent development of various technologies and methods needed. However, additional development of the initial ZDM model, measurement methods, sensors, cameras etc. is required in order to make ZDM generally available for all manufacturing and process industry companies. The initial ZDM model does not fulfill all posed requirements, but is a step towards the possibility to combine and integrate a number of necessary areas in various industrial settings. Further, the results are deemed as highly generalizable within the manufacturing and process industries as well as critical infrastructures with production and distribution environments. In addition, the possibility to inform the subsequent or previous steps in a production process or value chain enables the integration and interoperability of different systems. A question that needs to be asked is whether these companies will start to address and use ZDM as well as what that requires? Firstly, they need to be made aware and also see the potential, and subsequently they will need to get the knowledge, competence, technology and management support necessary to make these changes in both production processes and attitudes. Not all companies will be able to do so, whereas some will make a step-by-step plan and implement ZDM steadily. It will get easier as ZDM becomes a mainstream approach and have standard toolboxes available. Concerning future research, we intend to improve, refine and further develop the initial model for ZDM in a number of industrial cases.