This resource contains the Model Based System Engineering (MBSE) ontology being developed within the context of the H2020 EU Project AGILE 4.0 (2019-2022), and published as open access. The available files represent the meta-models, rendered by OWL, supporting the development of complex systems. The domains addressed by the meta-models are expanded, revised and maintained during the project. The ontology uploaded onto this page has been developed to address the development of complex aeronautical systems investigated in AGILE 4.0 Project, but it can be used to address any other kind of system. Domains currently included in the ontology: April 2021: meta-model for the modeling of system requirements. Additional information can be found in the project deliverable D1.3 "Process definition A4F for Application Case definition" (open access). June 2023: meta-model for the modeling of the whole system development process, including modeling of requirements, architectures and system design and optimization. Additional information can be found in the project deliverable D3.3 "AGILE 4.0 operational and trade-off process" (open access).