Unlike the other information system applications which all offer a direct and visible service to building users, the BOS is not visible to users. BOS is "infrastructure software" or even "core system" software or "middleware". Its main functions are:

• Integrate and manage the building's summary data model, its digital twin (unique description repository, dynamic state, behaviour model)

• Securely share repository data between the different applications of the information system (building API)

• Reliable and sustainable orchestration of data governance between applications

• Facilitate the development of new applications for the digital building

• Provide a setting application (a studio) allowing the creation of the digital twin and the configuration of the BOS services

The building is an "intermediary" asset in the scale of data processing. It functions on the edge or fog layer, between the land systems and the cloud. Its deployment mode can therefore be debatable (edge in the building, in a privet data center, in the cloud...). Several criteria must be taken into account to determine which deployment mode and therefore which data control level you wish to impose:

• reactivity (acting capacity in real time): edge/fog deployment mode preferred

• resilience and autonomy (continuity of the local services in case of a lost internet connection): edge/fog deployment mode preferred

• confidentiality: edge or private cloud deployment mode

• simplicity of deployment or management: cloud deployment mode preferred

• buying cost (CAPEX): cloud deployment mode preferred

The BOS offers a complete chain of data management through:

• the data integration coming from all the sources and data producers (Driver, API)

• the normalization of the data in a common shared language

• the dynamic contextualization of the data in the graph (digital twin)

• the persistent and dynamic storage of the data graph (typology of the database)

• the synchronization of the data with the consumers and producers of data

• the presentation of data in a secured and documented API

• the event management enabling the care of asynchronous transfers between IT and OT

• the securing of the chain of data processing

• the evolution capacity through the supply of an SDK and an open documentation

The BOS is an operating system dedicated to the building. The BOS is to the building what Windows is to the computer. A conductor that talks to all the applications and enabled each of them, via a specialized connector (driver, API, etc...), to become compatible with the whole of the system.

The BOS is therefore a data management platform that enables the convergence and the restitution of the building's data:

• the descriptive data: the BIM and the whole of the documentation

• the dynamic data: all the OT data (BMS, access control, fire security system...) and IoT data (connected offices, dynamic signalization...)

• the usage data: all the IT information systems that use the building (CMMS, ERP, MS365,...)

The BOS enabled to "push" the building reference frame (for instance building / floor level / room / equipment) to all the applications connected to the BOS