Digital twins are increasingly present in everyday language and their definition has evolved over time: initially seen as 3D representations of objects in computer-aided design, the Internet of Things has shifted them towards a connected mode. The digital twin is no longer a static representation of a physical asset but provides a dynamic representation of the state of the asset which can go as far as taking control of it. Following this evolution, digital twins find themselves more and more often mentioned in the context of Metaverse where they add the digital replication of objects.
Implementing these concepts and being able to define, deploy and use digital twins requires IT tools. The concept implicitly implying the need for interoperability, standardized approaches are of paramount importance.
It turns out that the NGSI-LD specification written by the ISG CIM group of ETSI is perfectly suited for this purpose. This specification, independent of any application domain, defines interfaces and data models allowing the exchange of data between businesses. The data is represented in the form of a knowledge graph which makes it possible to contextualize and link any piece of information in time and space. This specification is also strongly supported by the FIWARE foundation which provides a set of open-source software bricks compatible with this standard.
In this context, we have initiated within ETSI and in collaboration with the FIWARE foundation, a work of collection, illustration and classification of the use of the specification for digital twins. The use of NGSI-LD thus allows a representation of an object in atomic form (e.g. a sensor), in the form of a structure (complex object made up of subsets) or as a composition of systems (systems of systems). Several levels of digital twin capacities have been defined: descriptive (knowledge of past and current states), predictive (estimate of future props), prospective (analysis of options such as ‘what-if’ approaches), prescriptive (identification of operating parameters to reach a target operating point) or even diagnostic (for analyzing the operation of the system).
On July 5, a workshop was held during which the work was presented to a group of actors involved in digital twins and NGSI-LD in order to go through together and discuss the main elements of the technical report of the ISG CIM group. The following presentations were given and the discussions confirmed the interest of the NGSI-LD specification for the representation and use of digital twins.
- Introduction to DT and high level requirements extraction
- B – DT representation in the NGSI-LD context
- C – Actuation and DT service