CX-0002 Digital Twins in Catena-X v2.2.0
ABSTRACT
The Catena-X network is about accessing/sharing/providing/using data, formulated in the different use cases. This standardization scenario is about how the data, and the data models look like and how the modelling has to be done, so that data between ecosystem partners can be shared, lossless and in a machine-readable way. This document focuses on Digital Twins and their application and administration within Catena-X.
The purpose of this standard is to provide concepts and specifications in order to allow proper data provisioning with Digital Twins in Catena-X.
FOR WHOM IS THE STANDARD DESIGNED
This standard is designed as an implementable specification and thus is relevant for all technical roles concerned with APIs and Data Exchange in the Catena-X network
COMPARISON WITH THE PREVIOUS VERSION OF THE STANDARD
- Remove all normative references to the EDC implementation
- Declare outdated typization mechanism (asset:prop:type) optional
1 INTRODUCTION
1.1 AUDIENCE & SCOPE
This standard is relevant for
- data provider / consumer
- solution provider
The standard is applicable in the following cases for the following roles:
- all data providers who need to provide information via Digital Twins
- all data consumers and business application provider who need access to data provided via Digital Twins
- solution providers of a Digital Twin Registry
- onboarding service providers who need to offer core service of a Digital Twin Registry to their customers
- enabling service providers who need access to data provided via Digital Twins
- consulting service providers who need to explain how Digital Twins are implemented and/or used
1.2 CONTEXT AND ARCHITECTURE FIT
This section is non-normative
Catena-X creates a decentral, uniform, and consistent solution for data sharing in automotive industry. In this context, the exchange of data is an essential requirement for the success of this network. For this purpose, Catena-X provides various methods, tools, and standards to ensure semantic interoperability. Digital Twins have established themselves here as a central element for structuring and accessing data. With the help of defined semantics, both data provisioning and app development are simplified and encouraged.
1.2.1 Digital Twins in Catena-X
The term Digital Twin (DT) describes a digital representation of an asset sufficient to meet the requirements of a set of use cases.
Any asset - it can be an actual physical asset like an engine hood but also something virtual like a web service - has a digital representation with consistent semantics. Hence, Digital Twins adhere to the following characteristics:
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The DT has at least one Catena-X-wide unique identifier (ID).
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An asset can have more than one DT. However, each DTR may only contain a single DT for each asset.
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DTs organize a set of Aspects. A DT's set of aspects can be extended over lifetime.
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An Aspect of a DT includes both structural and behavioral data and models, including operations and simulation models.
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The semantics of an Aspect can be described via semantic models.
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A single Aspect can be connected to different heterogeneous data sources, including behavioral models.
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The DT can represent type assets (e.g., virtual prototype of a car) and instance assets (e.g., real car).
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A DT can cover the whole asset lifecycle including, e.g., the planning, production, sales, use, and decommissioning phases. However, in practice there may be more than one twin with different IDs representing different lifecycle phases, e.g., one twin for types and multiple twins for instances.
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The DT represents current available information about an asset, synchronized at a specified frequency and fidelity, which can be leveraged for simulation and business process integration.
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By using Aspects, a DT can reference other DTs to express "part of" or "consists of" relations.
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In the context of Catena-X Digital Twins are exposed to the Catena-X Dataspace according to the Dataspace Protocol (DSP).
1.2.2 Digital Twin Registry
A Digital Twin Registry (DTR) is an operated solution which lists Digital Twins and their respective Aspects. Each Digital Twin represents a single asset. Some basic information about the asset being represented is part of each entry in a DTR.
For each asset, several data sets in form of Aspects can be provided. These Aspects are referenced in each Digital Twin together with information about access to the Aspect endpoints.
Moreover, a DTR also offers basic discovery functionality to find Digital Twin(s) representing an asset under consideration.
In general, every data provider in the dataspace must decide how and where to operate a DTR.
The data provider needs to register all their Digital Twins including its respective Aspects to its DTR service in order to reveal its "offer" of sharing respective data sets.
The data offered by a Digital Twin via Aspects should be semantically described by a semantic Aspect metamodel conformant to CX-0003.
1.2.3 Asset Administration Shell
The Asset Administration Shell (AAS) is a key concept of Industry 4.0 (or "Industrie 4.0" in German), maintained by the Industrial Digital Twin Association (IDTA), and is used to describe an asset electronically in a standardized manner. The AAS is a standardized way to implement a Digital Twin. One of the main concepts of the AAS is the concept of Submodels, each of which can characterize the asset by describing its Aspects for different use cases and data consumers.
The specifications of the AAS offers a set of standardized API methods and resources to access data of a Digital Twin.
Also, an Asset Administration Shell Registry service and other services in the context of Digital Twins are standardized.
In Catena-X the semantics of a Submodel is described via an Aspect Model conformant to standard CX-0003, preferrable by using standardized properties conformant to standard CX-0044.
The following figure gives a high-level overview how the concepts relevant for this standard relate with each other and concepts from neighboring domains.
In general, the AAS has proven to be suitable for the following missions:
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representing data exchanged in a standardized way between two parties (API payload)
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Providing uniform access to data exchanged between two parties (API operations)
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Data discovery for the asset under consideration for exchange between two parties in a standardized way (Digital Twin Registry)
The Asset Administration Shell Reading Guide gives an overview for different stakeholders. This reading guide together with detailed technical documentation can be found in the Content Hub of the IDTA and on GitHub: https://github.com/admin-shell-io/aas-specs.
1.2.4 Architecture Overview
The Digital Twin Registry (DTR) component is a decentral component in the Catena-X dataspace. Typically, each data provider offers its own DTR, either using an enablement service provider that also operates the DTR for the data provider or operating it themselves.
The DTR does not only contain pure registration functionality but also basic discovery functionality based on asset identifiers. The corresponding APIs for this kind of discovery are specified in this document.
A DTR is accessed via a dataspace connector conformant to standard CX-0018. Business solutions first need to find the relevant connectors and thus negotiate with them for the relevant DTR. Additionally to EDC Discovery (see standard CX-0001), additional discovery services (see standard CX-0053) are provided to reduce the number of dataspace connectors that need to be accessed by the business application.
1.3 CONFORMANCE
This section is non-normative
As well as sections marked as non-normative, all authoring guidelines, diagrams, examples, and notes in this specification are non-normative. Everything else in this specification is normative.
The keywords MAY, MUST, MUST NOT, OPTIONAL, RECOMMENDED, REQUIRED, SHOULD and SHOULD NOT in this document are to be interpreted as described in [BCP 14], [RFC2119], [RFC8174] when, and only when, they appear in all capitals, as shown here.
1.4 PROOF OF CONFORMITY
All participants and their solutions will need to prove that they conform to the Catena-X standards. To validate that the standards are applied correctly, Catena-X employs Conformity Assessment Bodies (CABs).
1.4.1 Proof of Conformity for Digital Twin Registry Solutions
A Digital Twin Registry solution MUST provide http/REST APIs conformant to the openAPI specifications adopted in this document.
In case the Digital Twin Registry solution already has a valid certificate of the Industrial Digital Twin Association (IDTA) including the required service specification profiles the simplified certification process of Catena-X e.V. holds.
If there is no valid certificate available from the IDTA, Digital Twin Registry solution providers MUST prove their conformity by providing:
- An openAPI specification of the implemented endpoints.
- Documentation that the implementation's API responses match to the response structure of the required API specifications in this document.
A Digital Twin Registry Solution MUST include mechanisms that allow to ensure confidentiality and integrity of data, and compliance with antitrust laws.
On default, the read access to Digital Twins SHOULD be enabled by Digital Twin Registry Solutions to data providers only.
1.4.2 Proof of Conformity for Data Providers
A data provider MUST offer the http/REST APIs for its Digital Twin Registry service conformant to this specification.
In case the Digital Twin Registry solution already has a valid certificate of the Industrial Digital Twin Association (IDTA) including the required service specification profiles the simplified certification process of Catena-X e.V. holds.
The Digital Twin Registry service used by the data provider MUST be registered in the dataspace connector selected by the data provider.
A data provider MAY create and register Digital Twins using the http/REST APIs conformant to the openAPI specification as defined in this document.
The data provider MUST offer the READ operations for Digital Twins and its Aspects conformant to this specification.
The endpoints offered by the data provider MUST be made accessible to the dataspace as specified in this document or other use case related standards.
Appropriate usage policies conformant to standard CX-0018 and subsequent use-case-standards MUST be defined for accessing the Digital Twin Registry itself as well as for the Submodels.
Data providers MUST comply with antitrust law, i.e., competitively sensitive information (e.g. customer names, supplier names, prices, price models, internal knowhow, sales and/or purchasing strategies) MUST NOT be published via a DTR.
The data provider SHOULD use the unique identifier of the standardized Aspect Model conformant to CX-0003 when registering a new Submodel endpoint to a DTR.
A data provider SHOULD add specific asset IDs for each Digital Twin to enable discovery. Other CX-standards may make more specific demands for Data Providers which specific assetIDs are to be added.
A data provider SHOULD add information to available discovery services conformant to standard CX-0001 and CX-0053 - if available - to enable data consumers to find the relevant DSP-endpoints and thus the Digital Twin Registry the data consumer is interested in.
1.4.3 Proof of Conformity for Data Consumers
A data consumer, business application provider or enabling service provider MAY lookup the endpoints of the Submodels relevant for the use case using the http/REST APIs conformant to the openAPI specification as defined in this document.
Since there are several Digital Twin Registries in the dataspace data consumers, business application providers or enabling service providers MAY first lookup the available Digital Twin Registry endpoints of the relevant dataspace connectors using the corresponding standardized EDC discovery services (see standard CX-0001).
Additionally, data consumers MAY use standardized discovery services - if available -, e.g., to find a relevant dataspace connector for a specific company via its BPN (see standard CX-0053).