## 2 System and Process Analysis  
An analysis of the concrete printing process is conducted to trace the information along the digital workflow as well as to identify interactions between tasks, actors, and system elements, serving as the basis for the printing information modeling. The analysis is carried out in the context of the AEC industry, using BIM concepts to identify information exchange requirements and preserve semantic information, improving interoperability in the digital workflow. The concrete printing system and process analysis follow the methodology developed for BIM information delivery manuals [29], in which processes are discretized into tasks and the information exchanged between the tasks (i.e., inputs and outputs) is identified as information exchange requirements. In addition, a survey is conducted among concrete printing practitioners and researchers, whose results are integrated into the system and process analysis. The survey aims to address the following research points:  
* Common types of printing systems and software applications currently used for concrete printing;
* Work areas, actors, and tasks along the digital workflow of concrete printing;
* Information exchanged among the actors (e.g., inputs and outputs) and material-process interactions observed or relevant for each work area.  
The survey is designed as a questionnaire and shared online among 20 practitioners and researchers that have experience and publications in the domains of concrete printing, including design/architecture, civil engineering, mechanical engineering, material science, and robotics. The questions are formulated as a set of multiple-choice and open-ended questions regarding (i) printing systems and software applications employed for concrete printing; (ii) an overview of digital workflows, roles, and areas relevant to the work of practitioners and researchers; and (iii) information required and generated in their work areas. The open-ended questions are intended for practitioners and researchers to elaborate further on the multiple-choice answers. The results of the survey have been collected and processed to complement the system and process analysis with practical knowledge.  
From the survey, it is observed that the most common AM method is material extrusion and that robotic systems are favored for conducting research in concrete printing. Three main areas are identified, including AM design and planning, material science, and process control and optimization. The main inputs and outputs regarding slicing, toolpath planning, material design, and process simulation are collected. Material-process interactions are reported, including issues during pumping and extrusion due to variations in the material consistency and issues during the build-up of printed components due to insufficient green strength and setting time.  
Overall, the system and process analysis provide insight into the information exchanged along the digital workflow of concrete printing. Hence, the information exchange requirements provide the basis for translating concrete printing parameters and concepts into a general, valid semantic model. In the following subsections, the concrete printing system and the concrete printing process are described and analyzed. Then, the information exchange requirements are identified.