Markdown Version | Session Recording

Session Date/Time: 04 May 2022 13:00

T2TRG

Summary

The T2TRG meeting focused on digital twins, aiming to initiate formal research on the topic. The session included presentations from individuals involved with the Digital Twin Consortium (DTC) on connection profiles and a relationship-centric view of systems. Further discussions covered the Network Management Research Group's (NMgmtRG) work on network digital twins, the Semantic Definition Format (SDF) from the ASDF working group, and practical experiences from Ericsson Research on using SDF and DTDL (Digital Twin Definition Language) for building interoperable IoT-based digital twins. A key theme was the challenge of heterogeneity in IoT environments and the need for standardized approaches to defining and managing relationships and data models within digital twin systems. The meeting identified the need to capture terminology, existing IETF technologies, and gaps for future standardization and research.

Key Discussion Points

• Digital Twin Concept and Scope:

  • Digital twins are virtual representations of physical objects, synchronized, and distinct from the physical entity. They provide an abstraction layer for applications, offering insights and automation capabilities without dealing with low-level data.
  • The goal for T2TRG is to define terms, identify relevant IETF technology, and discover gaps for further standardization or research opportunities.
  • The definition of "digital twin" itself varies widely across different domains (e.g., full 3D simulation, static asset record, specific data points for simulation). A sense of those present indicates that clarifying "what digital twins mean to you" is a necessary first step in any specific discussion.

• Connection Profiles (CnSCP) - A Relationship-Centric Approach:

  • Presented by Anto Budiardjo and Toby Considine, CnSCP proposes a mechanism for system interoperability, incubated within the Digital Twin Consortium.
  • It shifts from an "endpoint-centric" to a "relationship-centric" view, where the value lies in managing the connections and interactions between systems.
  • CnSCP allows client and server systems to declare their capabilities (profiles) within a given context. A broker then finds compatible declarations and instantiates a connection profile model, enabling metadata (control plane) and potentially direct data flow (data plane).
  • Connection profiles are immutable specifications that define the function or information of a connection, contrasting with the dynamic nature of DNS for real-time discovery.
  • The system aims to normalize communication, making it dynamic and composable. It can dynamically adapt to new services (e.g., a "Trust Server" can change the nature of existing connections).
  • The broker's state provides intrinsic documentation of connection decisions, aiding maintainability and forensics.
  • CnSCP also enables the composition of meta-information by allowing nodes to combine inputs from multiple sources (e.g., voting systems).

• Interoperability Challenges and Data Models:

  • The inherent heterogeneity of IoT devices and platforms poses a significant challenge for digital twin implementations.
  • It was noted that current standards like Asset Administration Shells (AAS) define a "thing" (shell), whereas connection profiles model the "relationship" between two things, defining information from both ends simultaneously. This was highlighted as a key difference.
  • The Semantic Definition Format (SDF), developed by the ASDF working group, was presented as a way to define classes of things based on their interactions (affordances: Property, Action, Event) using JSON Schema-like data structures. SDF aims to harmonize data models across different IoT ecosystems by providing a common intermediate format.
  • Ericsson Research's experience in building conversion tools between IoT ecosystems (IPSO, DTDL) and SDF demonstrated that while 80% of models are easily mappable, "incompatible" or "missing" affordances (e.g., DTDL telemetry vs. IPSO LWM2M, DTDL relationships) require extensions to SDF or requests to other SDOs for feature alignment.
  • An extension to SDF for defining arbitrary relations (SDF Relation) is being worked on, supporting physical, functional, and semantic relations.
  • SenML was highlighted as a lightweight transport mechanism for time-series data, suitable for feeding IoT device measurements into digital twin platforms.

• Network Digital Twins (NMgmtRG):

  • The Network Management Research Group (NMgmtRG) is exploring applying digital twin concepts to networks themselves.
  • A network digital twin contains historical and real-time data, models (predictive, diagnostic), and interfaces for analysis, diagnosis, emulation, and control of the physical network.
  • This approach is seen as a key enabler for service-ordered cybersecurity, allowing detection of performance deviations by comparing actual network behavior against emulation.

• Knowledge Models in Digital Twins:

  • Beyond data and interaction models, the concept of "knowledge models" was introduced. These represent a higher abstraction of knowledge within a digital twin, often related to end-user facing aspects or system-level information.
  • The discussion raised questions about what kind of knowledge is relevant for a specific digital twin, how it should be accessed for inference, and the balance between local knowledge and a broader system-wide view (the "orchestrator's" role). The "art of digital twin" lies in determining the purpose and the useful slice of information to model, avoiding a one-for-one replica of complexity.

Decisions and Action Items

• Action Item: Anto Budiardjo to share links to relevant papers/documents (e.g., System Interoperability Framework) with the group.
• Action Item: All participants are encouraged to contribute relevant documents and information to the T2TRG GitHub repository by submitting pull requests.

Next Steps

• Continue Discussions: The discussions on digital twins, connection profiles, SDF, and related challenges will continue.
• Upcoming Wishing Meeting: A Wishing meeting is scheduled for two weeks from now. This lower-profile meeting will provide an opportunity for those interested to delve deeper into specific topics, including Michael Koster's ongoing work and other contributions. Information on this meeting will be circulated shortly.
• Document Development: The group should discuss the potential for developing a formal document (e.g., a research group draft) that collects and synthesizes the information and identified gaps. Submitting initial drafts for discussion is encouraged.
• Mailing List Engagement: Participants are encouraged to subscribe to and utilize the T2TRG mailing list for ongoing discussions.