# An open-BIM Approach to IoT Integration with Incomplete As-Built Data
## 5 Discussion  
The proposed approach supports data integration and interoperability in the digital built environment. The methodology enables the effective utilisation of BIM data in the use phase of the assets, supporting the dynamic decision making. Data from the three systems (BIM environment, IoT platform and BMS) were integrated and processed, focusing on the usability of the systems, building a new data structure on top of the existing data sets. Accordingly, information can be accessed and used, integrating and supporting the workflows and operations of the asset management team. The data re-aggregation and processing allows useful insights supporting operations in AM of cognitive buildings'. The methodology was developed employing open source software for better interoperability and cross-platform usage. In addition, the open standard IFC is used to support information management in the context of the cognitive buildings and smart built environments. IFC also allows the accessibility and integration capabilities to be increased in the development of further applications. The proposed approach, considering the Digital Twin system architecture proposed by [18], sits in the Data/Model integration layer and therefore supports the data integration for the development of multiple AM applications. IFC artefacts such as IfcAsset and IfcSharedFacilitiesElements were used in the proposed methodology to enable data integration, including the association with the controls and processes  
Figure 5: Anomaly detection application. (Figure 1) capable of supporting the automation of AM processes. Although the enrichment of the IFC schema with relevant AM information (e.g., contractors, resources, economic and financial data, maintenance planning data etc.) may be beneficial in the standardisation of the data collection and process, it can also result in storage and update issues. IFC is a static data format, which poorly supports the dynamic data update. Accordingly, the IRs definition phase in this methodology is vital to the success of this approach, since it includes the potential uses of data during operation. The case study demonstration was conducted using IFC 2x3, despite Version 4 [48] being available. The methodology can be adapted to the newest version for the data set based on Version 4. The application of the workflow to a digital model with more detailed geometries is possible, since the type entities have been generated in IFC for non-geometric virtual elements. The types can be related to the geometric objects by means of the IfcRelDefinesByType relationships, once they become available (e.g., after a refurbishment). After updating the IFC with geometries, further capabilities of the schema can be leveraged for location-enabled AM services (e.g., indoor navigation, H&S and agent-based simulations). Despite IFC being one of the primary means for interoperability and openBIM standards, it often needs to be converted to be fully usable in the development of software applications. A conversion procedure should be defined. BIMserver offers the possibility to export a sub-set of the imported IFC data, in order to achieve this result. Data can also be exported in JSON format, enabling the development of more generic and cross-domain applications [55]. This process should follow the MVD approach [52] in order to be repeatable and recognisable within the BIM domain, even though this approach is not extensively described in this article. Accordingly, it is possible to enhance the capabilities offered by the IFC model and IFC data, which can be queried through existing technologies and languages after being processed. We consider that the classification of BIM IoT data integration methods in Table 1 requires some extension with the advent of new technologies. The openBIM methodology proposed in this paper cannot be completely classified into any of those categories, as it shares some characteristics of multiple methods.