## 5 Discussion
### FM Core Competence: Operations and Maintenance (O&M)  
An important role in FM is to manage operations and maintenance of the facility. To do this, a good knowledge of building systems, structure, interiors and exteriors is required to ensure that systems operate efficiently, reliably, safely and in compliance with standards and regulations. This core competence is one of the most investigated, and one of the earliest studies was conducted by [PERSON] et al. (2013) [57]. The review showed a high growth rate in this category: ten out of fifteen articles were published in the past two years. Among the sixteen reviewed articles in this category, nine [57; 58; 59; 60; 61; 62; 63; 65; 70] are about Structural Health Monitoring (SHM). BIM-sensor integration for SHM has been addressed since 2013, and interest in this topic has remained constant over the years. Through data-driven SHM techniques, it is possible to improve information management on structures health, safety and hazard mitigation. However, traditional approaches are insufficient to manage a large amount of data and information to conduct systematic decision-making for future maintenance. The first attempt to create a connection between BIM and real-time data was made in 2013 by [PERSON] et al. [57]. In their research, sensors data are stored within the BIM model. Thisstrategy, however, could prove counterproductive as too many data from different types of sensors could weigh down the model. Subsequent studies [58; 59; 60; 61; 62; 63; 65] propose an information modelling framework for supporting SHM, which includes an external database to facilitate storage, sharing and utilisation of gathered data. Authors, in their studies, propose approaches that support dynamic visualisation (within the BIM model) of some key structural performance parameters and enable continuous updating and long-term data management, generating models compliant with the IFC standard. Such tools aim to facilitate decision-making on maintenance and risk management, avoiding manual errors resulting from visual inspection of the structures. Furthermore, in their study, [PERSON], [PERSON] and [PERSON] [63] introduce the concept of the Cyber-Physical System (CPS) and present a metamodel for describing it. In their paper, communication-related properties and behaviour of CPS applied for SHM are described. Moreover, system components relevant to communication are specified. Then, the metamodel to formally define a CPS is proposed and mapped into the IFC schema. On the other hand, the remaining articles that do not deal with SHM address equipment maintenance [66; 67; 68] and space management [64; 69; 71; 72]. Here too, collected sensors data are stored in an external database. The most relevant work in this area is, probably, the research of [PERSON] et al. [66]. They developed a data-driven predictive maintenance framework based on BIM, IoT and machine learning algorithms. Both Artificial Neural Network (ANN) and Support Vector Machine (SVM) are used to predict Mechanical, Electrical and Plumbing (MEP) components' future conditions with reasonably accurate results. Even if other prediction methods are taken into consideration, the proposed framework has significant implications: (a) fault alarming in an early stage avoiding failures; (b) future condition prediction (knowing in advance the failure timing); (c) minimising or avoiding overtime costs by preparing maintenance materials and tools ahead of time. Articles that deal with management and maintenance services [64; 69] focus primarily on occupancy control even if these systems are not always reliable due to their difficulty in counting people in crowded spaces. In the O&M context, a first conclusion may be made: reviewed articles suggest that future research should focus on facing challenges presented by managing and visualising data acquired during the whole life cycle of the facility, not only during a single phase. Data-rich BIM models will be necessary to support facilities monitoring and applications fully.