## 1 Introduction  
A smart city anchored by a cyber physical system can provide an intelligent solution capable of enhancing how urban services such as weather, energy and transport perform by combining data from the Internet of Things (IoT), building information modelling (BIM) and data mined from Internet sources and directly from inhabitants. These ingenious methods will significantly improve the efficiency of a city's operations. Although such improvements are expected to significantly improve infrastructure in the built environment, they frequently present technological obstacles that must be addressed. Indeed, the variety of data sources and knowledge modelling may limit the capacity for decision-making [1, 2]. There is also the important problem of defending against cyberattacks and appropriately enforcing access controls [3]. Integrating access management in smart cities in digital twins so that it can be applied in the built environment has proven to be a difficult task to date.To preserve the safety and identity of their physical twin, digital twins must be safe. Methodologies and data models are required to ensure effective protection across platforms, domains and scales [4, 5]. Access management approaches ensure that only relevant users who are correctly identified can access and utilize resources [6; 7]. Cyber-physical systems and IoT devices must be integrated with BIM datasets, digital twins, existing built environment services, current security standards, as well as newly developed user interfaces and the actors who use them. There have already been implementations in each of these fields, each with its own semantics, data structures and application programming interfaces (APIs). Therefore, in a bid to bring together such diverse attempts to produce a unified means of access management, this paper sets out to formalise the associated concepts, aligning them with the prevailing ontologies and concepts by means of semantic modelling. The aim of this paper is to answer the following research question: Can a semantically defined access management framework in smart cities prove suitable to manage the security of smart services deployed in the built environment? To answer this question, this paper follows a semantic approach, specifying and subsequently validating an access management framework in smart cities that is underpinned by formalized semantics. This access management framework in smart cities is built upon [8] validating this work through a set of use cases in a university context. This semantic approach is critical given the framework's intersection with prevailing built environment services, cyber-physical systems, IoT devices, physical built environment assets, digital twin and BIM datasets [9]. Thus, the current paper utilizes a rigorous ontology specification approach to formalize this framework. The remainder of this paper presents a background and related work of urban cities applications and cybersecurity functions; the methodology of a semantically specified access management framework in smart cities; defines the access management framework in smart cities; and presents ontology access management framework in smart cities development. The paper then develops and validates an access management ontology for built environment cyber-physical systems and inferences.