## 6 Conclusions and Future Work  
In this work, SysML has been adopted as the basic system engineering language to develop a DSML for tolerance analysis, implemented as a SysML profile: SysML4 TA. The main concepts of this language were depicted in different diagrams as a representation of the abstract syntax of the metamodel, but these concepts were implemented in SysML4 TA as 38 stereotypes, enriched with 60 OCL rules that support the domain-specific semantics. This paper also presented an initial library version (TA_Library) that specifies a basic set of reusable and consistent constructions for the effortless creation of the tolerance analysis model for a particular system. The use of these resources (SysML4 TA and TA_Library)following the proposed procedure facilitates the tolerance analysis modeling, assuring the consistency of the model according to the domain-specific semantics of the handled concepts. A case study to show the application of the methodology and its potential to analyze the geometric variability of a single-stage manufacturing process was also presented. We hope that this contribution will help to increase the acceptance of MBSE in the field of mechanical engineering and its application in an integrated way. As mentioned, SysML can be a key language in this important task to complete the digital thread that links the function with the manufacturing.  
In continuation of this research, three major work lines are planned. The first is the extension of the proposed DSML to incorporate semantics of system dynamics, which is necessary to develop consistent SysML models of hybrid simulation, where both the flow of materials and the flow of geometric variability are considered for multi-stage manufacturing processes simulation. Secondly, the automated model-to-model and model-to-text transformations will be deeply explored to create Modelica executable simulation models from SysML models and to support integration and synchronization with other models, for example, CAD models. Finally, a more ambitious work line is the specification of the concepts handled in the profile as an ontological model. This approach is compatible with the use of reasoners to support a deeper consistency assurance and knowledge inference about the domain. This additional ontological model must be also integrated with other models.  
Conceptualization, S.B.-N., P.R.C. and F.R.S.; methodology, S.B.-N. and F.R.S.; software, S.B.-N. and P.R.C.; validation, S.B.-N. and P.R.C.; formal analysis, S.B.-N. and F.R.S.; investigation, S.B.-N. and F.R.S.; resources, S.B.-N.; data curation, J.V.A.-N.; writing--original draft preparation, S.B.-N., P.R.C. and F.R.S.; writing--review and editing, J.V.A.-N.; visualization, S.B.-N.; supervision, P.R.C. and F.R.S.; project administration, P.R.C. and J.V.A.-N.; funding acquisition, J.V.A.-N. All authors have read and agreed to the published version of the manuscript.  
This research was funded by \"Pla de Promocio de la Investigacio a l'UJI\" of UNIVERSITAT JAUME I. Project title: \"Modelado e implementacion del gemelo digital para Sistemas Ciber-fisicos de Produccion (CPPS) orientado al aseguramiento de la calidad geometrica de producto\". Reference: UJI-B2020-33.  
The data presented in this study are available on request to the corresponding author.  
The authors declare no conflict of interest.