## 3 Methodology  
This section describes the paper's methodology. As described in Section 1, the research question being answered in this paper is as follows: Can a semantically defined access management framework in smart cities prove suitable to manage the security of smart services deployed in the built environment?  
Answering this question is important because whether an access management framework can secure data from digital twins is crucial to the possible creation of secure built environment solutions across a wide range of use cases in smart cities, such as healthcare, education and weather environments.  
This research question will be answered through the following steps:  
1. Define the concept of an access management framework for the built environment. It is our view that semantics must be utilised here to provide the formalised management of access management concepts for the built environment which can then, in turn, enable the wide range of tools and standards utilised in the built environment to be applied in an interoperable manner, thereby making it possible to make use of the defines access management concepts (see Section 4).
2. Eliciting the formal specification of the framework using the NeOn methodology (Section 5).
3. Development of the semantic access management framework in smart cities using both new and existing ontological resources (Section 5.2).
4. Validation of the framework whereby the ontology is applied in a use case via the CUSP platform [2]. This entailed the integration of the ontology and access management framework on the available platform so that a range of case studies could be applied to validate the framework. The results confirmed the ability of the ontology to function as intended in a digital twin setting, offering single sign-on and suitable access control [20] (see Section 6). The decision was taken to apply the NeOn approach for the second step owing to the fact that the supporting documentation was available, it offered a scenario-based approach and because of the available knowledge [21]. Consequently, digital twin access management for a built environment ontology was achieved using the NeOn approach [21; 22]. More specifically, this entails the application of a four-phases process:Phase 1 (Initiation): The initial phase specifies the ontological requirements, drawing upon insight gleaned from analysing case studies relating to the built environment (see Section 5), the findings of the survey [23] and a review of the empirical literature [9].  
Phase 2 (Re-use phase): The second phase involves analysing the available ontological resources to establish the ways in which they can be redeployed in the ontology that is devised. As part of this process, the semantic resources currently available in the access management and built environment domains will be factored in (see Section 5.2). In addition, there is an assessment of the resources that are non-ontological, enabling them to be formalised and re-engineered in a way that brings them into line with the ontological resources that are already in place. This second phase was undertaken for both case studies utilised to establish the requirements Section 5.3). The main purpose of this investigation is to establish the concepts and terminologies which will contribute to the ontology.  
Phase 3 (Design): The third phase involves developing the final ontology with reference to the specified requirements as well as the re-engineering of the non-ontological and ontological resources (described in Section 6).  
Phase 4 (Implementation): The developed ontology will be implemented and validated on a digital twin case study within the university buildings (described in Section 6.2).