## 3 Printing Information Model for Additive Manufacturing of Concrete Structures
### Conceptual Modeling of the Printing Information Model  
To conceptualize the information necessary for designing and planning concrete printing projects, aspects and interactions within concrete printing are summarized in the knowledge map and then structured in the semantic model. The knowledge map, shown in Figure 3, abstracts printed components according to process-related, material-related, and geometry-related aspects. Printed components are designed and planned within the context of a building or construction project, with design specifications that consider specific AM methods and printing systems. Printed components, represented by the _Component_ entity, can be described as outputs of manufacturing processes (_Process_ entity), are composed of materials (_Material_ entity), are characterized by specific geometries (_Geometry_ entity), and are situated within specific environments (_Environment_ entity). The manufacturing processes receive printable materials and digital models of the geometry of the components as inputs and are executed according to process parameters. The manufacturing process, to ensure manufacturability, may modify the geometry features of the components and the material properties due to the effects of the underlying physics of the manufacturing process. Material properties may constrain process parameters, e.g., viscosity limiting the material flow rate, and may modify geometry features, such as overhang angles and deposition deformation. The structural properties of the printed components are related to the material properties and the geometry features of the components. For example, the stiffness of printed components is related to the elastic modulus of the material and the inertia of the components. Furthermore, environmental conditions may modify material properties, e.g., yield strength during curing, as well as structural properties, such as durability. Based on the information exchange requirements, interactions between process-related and material-related aspects are identified within the knowledge map and further explored. It should be noted that, when identifying interactions within concrete printing, a general assumption is made that the AM methods and printing systems are selected before defining the geometry features and materials of the components. Material-process interactions include process parameters that are constrained by material parameters and material parameters that are modified via the manufacturing processes. Following the insight into material-process interactions presented in [9; 15; 16], on the one hand, the rheological behavior of concrete constrains process parameters during pumping and extrusion. On the other hand, process parameters can modify material properties, for example, by incorporating admixtures or local vibration during extrusion and deposition. Material-process interactions are usually evaluated by modeling the material and simulating the manufacturing process during design and planning of concrete printing projects, as has been shown in [13]. Building upon the knowledge map as an outcome of the system and process analysis, which aids in categorizing the input parameters and interactions in AM data modeling, the UML representation of the PIM model is developed. As mentioned above, the main parameters involved in concrete printing are coherently categorized into classes, and the interactions between the classes are described with semantic relationships. Moreover, the PIM model is refined in an iterative process based on knowledge-based reasoning. As a result, the PIM model is an understandable and instantiable metamodel that can be instantiated for BIM-based concrete printing in compliance with the Industry Foundation Classes (IFC) standard. When designing the PIM model, three simplifications are assumed to ensure software and hardware independence. First, the geometry information is assumed to be describable using concepts of standardized data models for geometry representations, such as the IFC standard.