## 2 Related Work
### Interaction of Supply Network and Production Planning and Control  
A supply chain is a goal-oriented connection of sites and companies, formed to optimize the flows of goods and information from suppliers to end users [8; 14]. The supply chain includes all functions involved in receiving and fulfilling a customer request whereas the goal of a supply chain is to generate value for the entire supply chain [6]. Supply chain implies that there is only one participant per stage. In fact, however, there could be several participants per stage: for example, several suppliers and customers of a manufacturer. Consequently, material and information can also flow between more than two parties [6; 8]. Chains are therefore actually networks, which is why the term supply network is more appropriate and will be furtherly used in this article. Only when existing concepts from the literature are referred to, their term is used (e.g., supply chain management and supply chain event management).  
Due to changing conditions in their environment (cf. Section 1), manufacturing companies are increasingly organizing themselves in supply networks. They expect this to lead to cost savings, increasing profitability, additional market opportunities, higher customer satisfaction and more agile processes [6; 8; 15]. Agility, in particular, requires that supply networks evolve from their original function of cost savings to combining the capabilities of partners [16]. Considering this, supply network integration aims at making the whole supply network more competitive through the value it adds overall [7]. Hence, competition has shifted from single companies to supply networks [7; 8].  
However, in integrated supply networks, often up to thousands of individual but coordinated decisions must be made per minute [17]. These have a strong influence on the profitability and success of the supply network [6]. In this context, the planning and decision-making tasks can be classified according to the planning horizon and the affected process of the supply network (cf. Figure 1). Long-term decisions usually have a time horizon of several years and affect the fundamental structure of the supply network. With a time horizon of one quarter to one year, mid-term decisions include activities to maximize efficiency considering the superordinate structure. On a weekly or daily basis, short-term decisions attempt to reduce uncertainty in the supply network and process incoming customer orders in the best possible way [6; 17].  
Across sites and companies, supply chain management aims to coordinate decisions on the flow of goods, information and money, in order to increase the competitiveness of the supply network and meet customer requirements efficiently [7; 17]. For a specific site, it is the task of PPC to pre-plan the continuous production program for several planning periods. Furthermore, to derive the required materials and resources from that and to implement the production program despite unavoidable disruptions such as staff shortages, machine malfunctions, supply delays and rejects [2]. Manufacturing control is especially responsible for the latter in a rather complex environment, since the number of possible order sequences alone grows exponentially with the number of machines and orders in a manufacturing system [2; 18; 19].  
Planning objects essentially give the link between PPC and supply network. Planning objects are, for example, production quantities or production dates that refer to future  
Figure 1: Planning and decision-making tasks in supply networks [17].  
states of individual elements of the supply network [15]. Presently, common PPC methods mostly use simulation and analytic approaches based on the planning objects to find optimal schedules. However, several approaches research on complementing or replacing these methods by ML [20].