## 7 Conclusions
This has been achieved through the specification and validation (on a university site) of the semantically defined access management framework in smart cities. This has shown that the semantically defined access management framework in smart cities can successfully represent the security requirements of smart services operating on a university site and then correctly enforce the defined permissions. The research limitations of this work and the future challenges it poses are as follows:  
**Limitation:** The case study was performed at a desk study that used produced real ontologies and simulated use of them. This might not be adequate to fully evaluate the functionality of the case study, though. It is therefore strongly encouraged that a live experiment be developed on an actual built environment asset. **Challenges:** The challenges and possibilities posed by digital twins in the built environment are identified and described. These problems concentrated on the need to improve current access management procedures in the built environment. This required analyzing the most recent technology in the disciplines of BIM, the Internet of Things, digital twins, smart cities and access management, as well as assessing industry views on access management in the built environment and the barriers to continued progress in this area. While the developed ontology provides a scalable starting point for expansion in additional new use cases, care must be taken to ensure that correct ontology re-use procedures are made, ensuring that existing ontological resources are re-used appropriate as opposed to inventing new and duplicate ontologies. The present study recommends the following future research areas as a way to further improve access management frameworks for digital twins in the built environment:  
Recommendation 1: The validation of the ontology is based on a case study at a university. In the future, the ontology will need to be validated on additional real-world digital twin implementations outside of a managed university environment. This is required for guaranteeing that the platform's final outcomes are secure and dependable. Recommendation 2: To verify the ontology, evaluate the created access management framework on a larger range of case studies. Recommendation 3: The creation of new software tools will further demonstrate the access management ontology's promise by enabling safe and scalable data sharing between digital twins and digital twin operators. This will be necessary to enable adequate and safe data sharing across the numerous digital twins that will be needed to represent the future smart cities. Conceptualization, K.A. and T.B. ; methodology, K.A. ; software, K.A. ; validation, K.A., T.B. and Y.R. ; formal analysis, T.B. ; investigation, Y.R. ; resources, T.B. ; data curation, K.A. ; writing--original draft preparation, K.A. ; writing--review and editing, T.B. ; visualization, R.A.; supervision, T.B. ; project administration, K.A. ; funding acquisition, K.A. All authors have read and agreed to the published version of the manuscript. **Funding:** This work is supported by the Deanship of the Scientific Research, Northern Border University, Arar, Kingdom of Saudi Arabia under grant number NBU-FFR-2023-0066. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable. **Data Availability Statement:** Not applicable. **Acknowledgments:** The authors extend their appreciation to the Deanship of Scientific Research at Northern Border University, Arar, KSA, for funding this research work through project number \"NBU-FFR-2023-0066\". **Conflicts of Interest:** The authors declare no conflict of interest.