4 General information

4.1 Introduction to Digital Product Passport

The European Ecodesign for Sustainable Products Regulation (ESPR, Regulation (EU) 2024/1781) establishes the Digital Product Passport (DPP) as a mandatory requirement for products placed on the EU market. The technical standards for DPP implementation are being developed by CEN/CLC/JTC 24 as a series of European standards:

EN 18219:2026 (Unique Identifiers) defines globally unique product identifiers and the three levels of granularity (Model, Batch, Item) at which they apply.

EN 18220:2026 (Data Carriers) specifies the data carriers (e.g. QR codes, RFID) used to link physical products to their digital passports.

EN 18221:2026 (Data Storage) defines requirements for DPP data storage and persistence.

EN 18216:2026 (Data Exchange Protocols) specifies the protocols for exchanging DPP data between systems, i.e. HTTP REST.

EN 18222:2026 (API) defines the application programming interfaces, leveraging the HTTP REST protocol, for accessing DPP data. This API is implemented in the OPC Foundation's UA Cloud Library.

EN 18223:2026 (System Interoperability) defines the semantic data model that this companion specification maps to OPC UA. It specifies the core entities: DigitalProductPassport, DataElement, DataElementCollection, SingleValuedDataElement, MultiValuedDataElement, MultiLanguageDataElement and RelatedResource.

EN 18239:2026 (Security) defines access rights, security, and business confidentiality.

EN 18246:2026 (Data Auth) defines data authentication, reliability and integrity.

This OPC UA companion specification maps the EN 18223:2026 data model to OPC UA ObjectTypes for real-time browsing of DPP data in an AddressSpace, and to OPC UA DataTypes for read/write of complete DPP instances. The DataElementType hierarchy mirrors the EN 18223 entity model, with properties mapped to OPC UA Variables and dictionary references preserved to maintain semantic traceability to the underlying data dictionaries.

For example, the companion specification may be used by a tool to convert DPP templates from the IDTA and Catena-X (provided by these organisations in Asset Admin Shell JSON or XML format only) into OPC UA NodeSet files for storage in the UA Cloud Library. This process is shown in Figure 1

Figure 1 - AAS Template to DigitalProductPassport Conversion Process

An example of an overall DigitalProductPassport architecture for batteries described by a is depicted in the Figure 2 which makes use of open-source components provided by the OPC Foundation.

Figure 2 - Digital Product Passport architecture for batteries

In Figure 2, the Companion Specification will be used within the UA Data Processor, reading battery production data, battery usage data and battery Bill of Materials (BoM) from different data sources and constructing a Digital Battery Passport (DBP) from this information. The DBP is then stored in OPC UA NodeSet file format and uploaded to the UA Cloud Library for retrieval via the DPP API by the battery's customer (called Product Customer in the diagram).

4.2 Introduction to OPC Unified Architecture

4.2.1 What is OPC UA?

OPC UA is an open and royalty free set of standards designed as a universal communication protocol. While there are numerous communication solutions available, OPC UA has key advantages:

A state of art security model (see OPC 10000-2).

A fault tolerant communication protocol.

An information modelling framework that allows application developers to represent their data in a way that makes sense to them.

OPC UA has a broad scope which delivers for economies of scale for application developers. This means that a larger number of high-quality applications at a reasonable cost are available. When combined with semantic models such as DigitalProductPassport, OPC UA makes it easier for end users to access data via generic commercial applications.

The OPC UA model is scalable from small devices to ERP systems. OPC UA Servers process information locally and then provide that data in a consistent format to any application requesting data - ERP, MES, PMS, Maintenance Systems, HMI, Smartphone, or a standard Browser, for examples. For a more complete overview see OPC 10000-1.

4.2.2 Basics of OPC UA

As an open standard, OPC UA is based on standard internet technologies, like TCP/IP, HTTP, Web Sockets.

As an extensible standard, OPC UA provides a set of Services (see OPC 10000-4) and a basic information model framework. This framework provides an easy manner for creating and exposing vendor defined information in a standard way. More importantly all OPC UA Clients are expected to be able to discover and use vendor-defined information. This means OPC UA users can benefit from the economies of scale that come with generic visualisation and historian applications. This specification is an example of an OPC UA Information Model designed to meet the needs of developers and users.

OPC UA Clients can be any consumer of data from another device on the network to browser based thin clients and ERP systems. The full scope of OPC UA applications is shown in Figure 3.

Figure 3 - The scope of OPC UA within an enterprise

OPC UA provides a robust and reliable communication infrastructure having mechanisms for handling lost messages, failover, heartbeat, etc. With its binary encoded data, it offers a high-performing data exchange solution. Security is built into OPC UA as security requirements become more and more important especially since environments are connected to the office network or the internet and attackers are starting to focus on automation systems.

4.2.3 Information modelling in OPC UA

4.2.3.1 Concepts

OPC UA provides a framework that can be used to represent complex information as Objects in an AddressSpace which can be accessed with standard services. These Objects consist of Nodes connected by References. Different classes of Nodes convey different semantics. For example, a Variable Node represents a value that can be read or written. The Variable Node has an associated DataType that can define the actual value, such as a string, float, structure etc. It can also describe the Variable value as a variant. A Method Node represents a function that can be called. Every Node has a number of Attributes including a unique identifier called a NodeId and non-localized name called as BrowseName. An Object representing a 'Reservation' is shown in Figure 4.

Figure 4 - A basic Object in an OPC UA Address Space

Object and Variable Nodes represent instances and they always reference a TypeDefinition (ObjectType or VariableType) Node which describes their semantics and structure. Figure 5 illustrates the relationship between an instance and its TypeDefinition.

The type Nodes are templates that define all of the children that can be present in an instance of the type. In the example in Figure 5 the PersonType ObjectType defines two children: First Name and Last Name. All instances of PersonType are expected to have the same children with the same BrowseNames. Within a type the BrowseNames uniquely identify the children. This means Client applications can be designed to search for children based on the BrowseNames from the type instead of NodeIds. This eliminates the need for manual reconfiguration of systems if a Client uses types that multiple Servers implement.

OPC UA also supports the concept of sub-typing. This allows a modeller to take an existing type and extend it. There are rules regarding sub-typing defined in OPC 10000-3, but in general they allow the extension of a given type or the restriction of a DataType. For example, the modeller can decide that the existing ObjectType in some cases needs an additional Variable. The modeller can create a subtype of the ObjectType and add the Variable. A Client that is expecting the parent type can treat the new type as if it was of the parent type. Regarding DataTypes, subtypes can only restrict. If a Variable is defined to have a numeric value, a subtype could restrict it to a float.

Figure 5 - The relationship between Type Definitions and Instances

References allow Nodes to be connected in ways that describe their relationships. All References have a ReferenceType that specifies the semantics of the relationship. References can be hierarchical or non-hierarchical. Hierarchical references are used to create the structure of Objects and Variables. Non-hierarchical are used to create arbitrary associations. Applications can define their own ReferenceType by creating subtypes of an existing ReferenceType. Subtypes inherit the semantics of the parent but can add additional restrictions. Figure 6 depicts several References, connecting different Objects.

Figure 6 - Examples of References between Objects

The figures above use a notation that was developed for the OPC UA specification. The notation is summarized in Figure 7. UML representations can also be used; however, the OPC UA notation is less ambiguous because there is a direct mapping from the elements in the figures to Nodes in the AddressSpace of an OPC UA Server.

Figure 7 - The OPC UA Information Model notation

A complete description of the different types of Nodes and References can be found in OPC 10000-3 and the base structure is described in OPC 10000-5.

The OPC UA specification defines a very wide range of functionality in its basic information model. It is not required that all Clients or Servers support all functionality in the OPC UA specifications. OPC UA includes the concept of Profiles, which segment the functionality into testable certifiable units. This allows the definition of functional subsets (that are expected to be implemented) within a companion specification. The Profiles do not restrict functionality, but generate requirements for a minimum set of functionalities (see OPC 10000-7).

4.2.3.2 Namespaces

OPC UA allows information from many different sources to be combined into a single coherent AddressSpace. Namespaces are used to make this possible by eliminating naming and id conflicts between information from different sources. Each namespace in OPC UA has a globally unique string called a NamespaceUri which identifies a naming authority and a locally unique integer called a NamespaceIndex, which is an index into the Server's table of NamespaceUris. The NamespaceIndex is unique only within the context of a Session between an OPC UA Client and an OPC UA Server- the NamespaceIndex can change between Sessions and still identify the same item even though the NamespaceUri's location in the table has changed. The Services defined for OPC UA use the NamespaceIndex to specify the Namespace for qualified values.

There are two types of structured values in OPC UA that are qualified with NamespaceIndexes: NodeIds and QualifiedNames. NodeIds are locally unique (and sometimes globally unique) identifiers for Nodes. The same globally unique NodeId can be used as the identifier in a node in many Servers - the node's instance data can vary but its semantic meaning is the same regardless of the Server it appears in. This means Clients can have built-in knowledge of of what the data means in these Nodes. OPC UA Information Models generally define globally unique NodeIds for the TypeDefinitions defined by the Information Model.

QualifiedNames are non-localized names qualified with a Namespace. They are used for the BrowseNames of Nodes and allow the same names to be used by different information models without conflict. TypeDefinitions are not allowed to have children with duplicate BrowseNames; however, instances do not have that restriction.

4.2.3.3 Companion Specifications

An OPC UA companion specification for an industry specific vertical market describes an Information Model by defining ObjectTypes, VariableTypes, DataTypes and ReferenceTypes that represent the concepts used in the vertical market, and potentially also well-defined Objects as entry points into the AddressSpace.