## 1 Introduction
The way to collect manufacturing information (i.e., welding) brings with it the necessity to integrate the heterogenic nature of the information that comes from different sources, which could lead to a divergent way of interpreting its meaning, causing misinformation, misleads, and errors that increase project costs and development time [11; 12]. This practice is known as knowledge-based engineering (KBE) and it is able to capture engineering knowledge systematically into the design system, with the aim to support the engineering activities by the re-use of previous experience [13]. Recently, ontologies were used as a tool to implement KBE systems showing the potentials in promoting semantic interoperability, exchanging information among engineering tools, and pointing out the inconsistency among several disciplines [14]. The ontology allows creating functional relations between DFMA principles and the necessary interpretation of the virtual model available by the CAD [15]. The developed tools allow the analysis of CAD models, integrating design for manufacturing principles, which contribute to manufacturing time and rework reduction [16; 17; 18]. However, all the mentioned systems do not consider the specific peculiarities of the welding processes which are characterized by complex geometries and multidisciplinary effects. Significant research in DFW has focused on the development of computer systems that can support manufacturability and production cost assessment within the early stages of product design. Three main approaches are often used for the development of such CAD-based systems. The first refers to the process planning approach and it allows extracting the CAD assembly features required to automatically generate welding paths and determining welding parameters [19; 20]. Even if the extraction of CAD assembly features is an interesting part of the preliminary analysis of the CAD model, the final aim does not fit with the possibility to anticipate welding issues during the product manufacturing. The second method refers to the rule-based approach in which DFW ruleswere linked with geometrical data retrieved from the CAD model by using object-oriented and feature-based methods, providing a specific application (i.e., automotive) [21,22]. The third method refers to the case-based approach providing models and algorithms to determine if welding is an appropriate manufacturing process for a given design or to enable the design of the weld (i.e., suitable base materials, the welding process, and filler metals process) [23, 24, 25]. Even though these studies look promising in the integration of DFW principles in the early phases of product development, DFW suffers from real interoperability with 3D CAD systems and DFW principles are currently being applied downstream of the 3D modeling, by following the well-known guidelines available from the literature and company's know-how (tacit internal knowledge). Thus, manufacturability issues are identified later in the design process, when many design decisions have been finalized, which forces manufacturing engineers to either request a formal design review. Iterations required by the project revision due to manufacturing and assembly issues have tremendous impacts in terms of time and rework needed, incurring greater production costs and delays in product launch, or resulting in designs that may cause significant additional costs during production. The management of information flow between members of the project team in manufacturing companies depends on the rules adopted in the companies and often varies significantly. The possibility to re-inject manufacturing knowledge within the design department of the system, especially in the case of welded structures, is a very complex task and a challenge in the modern industry. The integration of DFW with computer-aided design software can reduce redesign and control activities, which are knowledge-intensive engineering tasks, and finally, the overall project cost [26].