An extension of Thing Descriptions from the Web of Things for Digital Twins

Background: Digital Twins are becoming ubiquitous in a range of domains, such as construction or e-health. Due to the numerous applications where Digital Twins can be adopted, they have to manage heterogeneous cross-domain data that is consumed by third-party service or domain experts. Digital Twins may allow for performing operational commands that are transformed into actions in the physical world; these operations can be grouped into processes. In the domain of construction, a European Project named COGITO was proposed, in which a Digital Twin is used to simulate the construction processes carried out in three railway stations in Europe (Spain, Denmark and Austria). The lack of interoperable data due to heterogeneity in the APIs of the physical layer, the complexity that entails managing these data at the digital model, and the difficulty of orchestrating the data exchanged among the advanced features have been the roadblocks in the project. Methods: The problems have been addressed by adopting the W3C Web of Things (WoT) standard, by using Thing Descriptions. Although the challenges are specific for the COGITO project, they could be found in any Digital Twin proposal. Thus, the article presents how they are solved and addressed in COGITO. Results: The results demonstrate that relying on a Knowledge Graph for the provenance, another for describing a distributed architecture of semantic interoperability services and a final one for data, allows to build a distributed Digital Twin over heterogeneous data sources that provide semantic interoperable data in each digital layer. Conclusions: The lack of a Digital Twin standard highlights the necessity of adopting existing standards and extending them in order to adapt their suitability to the Digital Twin context. Hence, the article presents how WoT is helpful for addressing the challenges, and how it could be extended in the future to support Digital Twins.