## 2 Research Methodology  
This research is based on a design science research method (DSRM) suitable for engineering innovation research projects [7]. The DSRM is structured in five stages: (1) identification of observed problems and motivations, (2) definition of the potential solution, (3) design and development, (4) demonstration and (5) evaluation. Figure 1 shows a summary of these stages, along with their objectives and the tasks and tools required.  
The first stage focused on understanding the challenges in DDWSS design project approaches. Moreover, the current research and designing standards were collected; these include the Regulation on Domestic Installations of Drinking Water and Sewerage (Reglamento de Instalaciones Domiciliarias de Alcantarillado y Agua Potable, RI-DAA [8]), a Chilean standard. Additionally, complementary standards are applied for verification, determination of materials, identification of the ranges of allowable values and the presentation of deliverables. For this paper, the following Chilean standards ([[https://www.inn.cl/nch-aprobadas](https://www.inn.cl/nch-aprobadas)]([https://www.inn.cl/nch-aprobadas](https://www.inn.cl/nch-aprobadas)), accessed on 8 September 2022) were used: NCh 398, NCh 399, NCh 951, NCh 1635, NCh 2038, NCh 2485, NCh 2592 and NCh 2836.  
The literature review was used a tool in this first stage to identify research articles and documented projects related to key concepts: automation using BIM, parametric design automation and plumbing design in BIM environments. The Google Scholar, Scopus and Web of Science platforms were used to search for relevant literature published between 2000 and 2022.  
In the second stage, we developed automatised methods for optimising time, costs, human resources and the overall development of DDWSS design projects. This goal was achieved by creating algorithms and automatic processes. The parameterisation of regulatory calculation guidelines in a BIM environment reduces the amount of manual work required during the design stage of DDWSS projects.  
In the third stage, we identified a sequence of activities based on the literature review and determined the different functionalities of the selected software for the development of the expected solution:  
1. Defining the format for the input data of the project so that it corresponds to parameters obtained both directly and indirectly from the three-dimensional model;
2. Defining the way to extract these data into spreadsheets, if required;
3. Defining the procedure for transferring the complementary project information that corresponds to the indirect input data of the model--i.e., project characteristics that cannot be obtained from the model and must be entered by the user;
4. Determining the iterative method for the calculation and verification of the resulting parameters as a convergence process;
5. Defining the method for the insertion of data into the BIM software, which are then returned to the model and modify the initial values of the project--for instance, pipe diameters;
6. Configuring deliverables corresponding to floor plans and tabulations with results in a standard plan, as defined by the RIDAA.  
In the fourth stage, the described workflow was implemented for a simple case study with basic characteristics involving a residential building with a distributed system on a  
Figure 1: Research methodology workflow.  
single floor. This process involved checking the functionality of the algorithm and the data management for the design parameters.  
Finally, in the fifth stage, a more complex case study was introduced to evaluate the behaviour of the programmed algorithms. This case study corresponded to a known and previously solved real-world project, which allowed the results obtained to be compared with values resulting from traditional calculation. The comparison of the results was conducted by calculating the relative errors with the known values of the project.