iiRDS and VDI 2770: Two Standards in Technical Documentation
At first glance, iiRDS and VDI 2770 appear to be competing for dominance as the exchange format for digital technical documentation. But a closer look behind the scenes reveals that significant effort has gone into aligning the two standards.
Table of Contents
Standards – Why They Matter
The digitalization of modern industry is also transforming technical documentation. Increasingly individualized product variants, complex global supply chains, and a multitude of involved IT systems are driving the volume of technical documents ever higher. Classifying metadata and standardized file formats are the tools of choice in information management for keeping things under control. However, these measures are often company-specific or heavily dependent on the software in use — which sacrifices the key advantages of cross-organizational information exchange.
The PDF format currently serves as a de facto standard for delivering digital manuals. In most cases, PDF manuals offer no more value than a scanned version of a paper document. They provide no further options for filtering, assignment, or organization. This is a paradoxical situation when you consider the wealth of metadata and structure available in modern content management systems. During publication, a large portion of valuable additional information is discarded, and recipients are left with the difficult task of categorizing the content themselves. Content delivery portals, in particular, benefit greatly from so-called "intelligent information" and can thereby generate real added value for users.
Standards for Information Exchange
- DDC – Document kind classification code; the classification for technical documents defined in DIN EN 61355, which is also referenced in VDI 2770.
- eCl@ss – A data standard for classifying products and services based on internationally standardized characteristics; used in VDI 2770 for object referencing and can also be used in iiRDS.
- iiRDS – intelligent information Request and Delivery Standard; an open-source standard developed by the iiRDS Consortium for the exchange of digital technical documentation; specifies a container format and an RDF-based domain ontology.
- IRI – Internationalized Resource Identifier; the internationalized version of the Uniform Resource Identifier (URI); a globally unique identifier in a defined form, with subtypes URL (e.g., web addresses) and URN (e.g., ISBN).
- IRDI – International Registration Data Identifier; the internationally standardized identifiers used by eCl@ss for referencing objects.
- RDF – Resource Description Framework; a method for describing relationships between resources through statements called triples; can be expressed in various formats, such as RDF/XML; forms the basis for the iiRDS metadata file.
- VDI 2770 – A guideline by the VDI that defines minimum requirements for the exchange of digital manufacturer information for the process industry; specifies a container format and an XML-based metadata schema.
- XML – Extensible Markup Language; a media-neutral markup language for structured data, used for capturing content or serializing metadata.
The Hope for a Standardized Exchange Format
Companies' hopes rest on a standardized exchange format for digital technical documentation. Such a format could significantly simplify both communication with suppliers and internal information exchange. At the same time, it can serve as a stable foundation for modern data-driven content use cases. Developed by an independent body and aligned with industry requirements, the standard is intended to bridge organizations and systems, enabling a lossless flow of information. Metadata plays a central role in assigning content to product and information types and should be made explicitly accessible.
Two separate initiatives have formed to establish technical rules with these goals in mind:
- A working group of the Association of German Engineers (VDI) tasked with developing minimum requirements for digital manufacturer information for the process industry; the primary goal is to standardize the exchange between suppliers and customers in the process industry and to incorporate the framework into national and international standards.
- A working group of tekom tasked with developing an exchange format for technical communication content, with the primary goal of enabling intelligent delivery of information and vendor-neutral exchange between systems (e.g., content management systems and content delivery portals); additionally, the working group aims to standardize information-related metadata in a domain ontology wherever this is broadly useful.
Over several years, two specifications have emerged that propose a defined categorization for technical information. They also specify file formats for content and metadata, and define the structure of an exchange package. These are the iiRDS and VDI 2770 standards.
iiRDS and VDI 2770 – Two Standards, One Goal?
Both initiatives share the same objective. However, they implement the resulting requirements differently. VDI 2770 focuses on entire documents and, by mandating PDF as a required format, reflects the current state of technical documentation. iiRDS takes a different approach: the standard moves away from the document context and is fundamentally based on a topic-oriented approach with various content formats and semantic relationships. Depending on the situation and target audience, relevant information units can be delivered to the user.
To model the semantic relationships needed for user-centric content delivery, iiRDS uses an ontology specifically designed for technical documentation. This ontology provides a framework for assigning metadata. Based on a collection of typical use cases, particular emphasis was placed on contextual references (activity, point in time, target audience) and references to objects (product, assembly, tool).
Whether VDI 2770 or iiRDS — each approach has advantages and disadvantages that affect which format is the right fit for a given organization. Many suppliers currently delivering paper documentation with their technical products are more likely to adopt the VDI guideline, as it allows them to meet the minimum requirements of large buyers going forward. The requirements for modular, topic-oriented documentation are more effectively addressed by iiRDS.
Both standards represent an important foundation of modern information management: the unambiguous identification of content, metadata, and (physical) objects such as products or assemblies. Only through this can relationships be formed and universal interoperability be guaranteed. While iiRDS consistently uses IRIs (whose specialization, the URL, is familiar from the internet), VDI 2770 relies on a combination of domain-specific IDs, the IRDIs used in eCl@ss, and specific codes — such as DCCs from DIN EN 61355 or ClassIds for VDI 2770 document categories. Since version 1.0, these can be specified in iiRDS as so-called "complex identities," ensuring that unambiguous assignment across both standards remains possible.
Similarities and differences are also evident in the concrete technical specifications. Both standards use a ZIP archive as their container format. However, the specifications for the file and directory structure within the container differ. VDI sets strict rules for content formats (PDF/A and optional source files). In iiRDS, only the iiRDS/A variant specifies rules for file formats: XHTML5 or PDF/A.
In VDI 2770, the core metadata is implemented per document as an XML file. In iiRDS, a single RDF file is used for all files, which also defines the relationships within the overall package. In the VDI guideline, this function is handled by the so-called main document at the top level (a kind of table of contents) along with the nested structure of the package contents.
The use of a single RDF file also means that iiRDS packages, due to their high complexity, can only be created and read by specialized systems. The VDI format, by contrast, maintains the possibility of direct human editing thanks to its relatively simple structures and XML-based metadata.
iiRDS and VDI 2770 – The Differences
VDI 2770 integrates DIN EN 82045-2 and DIN EN 61355 and incorporates a significant portion of requirements from document management. iiRDS, by contrast, focuses on semantic and functional relationships between different types of content and product components. Pure administrative metadata — such as release approvals or status transitions — takes a back seat.
Furthermore, iiRDS follows an "open world" approach when modeling metadata. This approach, common in the semantic web, allows users to define new values and relationships based on the ontology. All modeling is generally permitted unless explicitly restricted. It is explicitly intended, for example, that company-specific values for target audiences or product lifecycle phases can be added. This stands in contrast to the VDI guideline, which prescriptively defines which modeling options are permitted.
Due to these "open" and "closed" modeling approaches, and the fact that the tekom standard allows not only documents but also a wide variety of other information units, the VDI guideline's metadata model can be viewed as a subset of iiRDS. Based on appropriately prepared and regulated iiRDS data, a VDI 2770 package can therefore be generated — albeit often with some loss of information at the metadata level. This becomes clear when looking at document classification. The 20 predefined document types in iiRDS can be clearly mapped to the twelve document categories in VDI 2770. The reverse mapping, however, is not possible without additional knowledge.
Document Types in iiRDS and VDI 2770
iiRDS (Document Type) | VDI 2770 (Document Category) |
Administration Manual | Operation |
Assembly Instructions | Assembly, Commissioning, Disassembly |
Bill of Materials | Components |
CE Declaration of Conformity | Certificates, Test Reports, Declarations |
Certificate | Certificates, Test Reports, Declarations |
Contractual Document | Contract Documents |
Electronic Nameplate | Identification |
Identification Document | Identification |
Installation Instructions | Assembly, Commissioning, Disassembly |
Maintenance Instructions | Inspection, Maintenance, Testing |
Operating Instructions | Operation |
Parts Catalog | Spare Parts |
Plan | Drawings/Plans |
Quick Reference Guide | Assembly, Commissioning, Disassembly |
Repair Instructions | Repair |
Safety Instructions | General Safety |
Sales Catalog | Contract Documents |
Specification | Technical Specification |
Technical Drawing/Diagram | Drawings/Plans |
Transport Instructions | Assembly, Commissioning, Disassembly |
Standards in the Committees
In March 2016, the tekom working group "Information 4.0" began its work with the goal of defining a uniform exchange format for technical documentation. In April 2017, the first preliminary draft of "iiRDS – intelligent information Request and Delivery Standard" was presented to the public. At around the same time, the VDI's "Operation of Process Engineering Plants" division was working on "VDI Guideline 2770, Part 1." In October 2017, the two committees held their first meeting to explore the commonalities and differences in their standardization efforts.
Following the decision to collaborate, the adjustments required for compatibility were documented in an internal exposé and gradually implemented within the working groups. Starting with version 0.9 of iiRDS, the document management metadata mandatory in VDI 2770 was integrated. This includes, for example, identity domains, content lifecycle phases, release status transitions, and references to actors. In addition, missing document types, product lifecycle phases, and information topics were added. After the initial publication of the VDI guideline, it was adjusted with regard to subfolders in document containers to maintain compatibility with iiRDS. Both standards moved toward each other to prevent fragmentation in the exchange of digital documentation.
Following the founding of the iiRDS Consortium in early 2018 and the publication of "iiRDS 1.0" in April, efforts to collaborate were resumed and expanded. At the end of 2018, the consortium commissioned an "Implementation Guide." The guide describes a concrete conversion between the formats and outlines the possibility of so-called hybrid packages. In the course of this, the committees established further mappings between the metadata of the two frameworks and agreed to mutually attend each other's meetings.
In the meantime, both standards have been further developed. Version 1.0.1 of iiRDS is available, and the VDI guideline was published at the beginning of April 2020. An updated version of the "Implementation Guide" is therefore needed and was expected to be available in the first half of 2020. The strong interest from industry in a cross-standard solution has shown that the path of collaboration was both correct and necessary to make interchangeable digital documentation possible.
Hybrid Package: Compliant with Both iiRDS and VDI 2770
The central concept of VDI Guideline 2770 is the mapping of the physical product structure through a nesting of document containers. This "matryoshka principle" (named after the image of Russian nesting dolls) makes it relatively easy to integrate — or replace — the documentation of a component manufacturer within the overarching documentation of the overall product. Each container carries its own metadata and administrative information. This allows a straightforward assembly of the complete documentation, provided all suppliers deliver their documentation compliant with VDI 2770.
Until now, iiRDS only provided for a single delivery container in which content receives a hierarchical structure exclusively through metadata. While subfolders are possible within such a container, they have no semantic significance. As for the nesting of multiple iiRDS containers within one another, the specification up to and including version 1.0.1 made no concrete statements. A direct mapping of the VDI logic was therefore not straightforwardly possible.
Matryoshka containers are a useful extension in the general iiRDS use context — for example, when it comes to integrating supplier documentation. To determine the concrete form of these nested packages, a foundational vote on various implementation options was held within the consortium in October 2019, a so-called "Technical Ballot." The preferred solution is currently being anchored in the iiRDS specification and will be incorporated into the standard with the upcoming version 1.1. Together with the final version of the VDI guideline and the updated "Implementation Guide," iiRDS 1.1 thus forms the basis for compatibility between the two standards.
This gives rise to a new element in the series of package formats: a hybrid package that is compliant with the requirements of both standards (fig. 01). It can be read by both VDI 2770 software and iiRDS-compatible systems, thus also fulfilling any VDI 2770 purchasing requirements of large corporations. It should be noted, however, that while the content is identical for both reading modes, the metadata is not. The iiRDS file in such a combined container contains significantly more information than its VDI counterpart. Whether the hybrid package will prevail in practice or whether two separately generated packages will be delivered in parallel remains to be seen.
Both Standards Have Their Right to Exist
Both standards have their right to exist — not least due to their different areas of focus — and will coexist for the foreseeable future. They are, however, by no means incompatible; rather, each can benefit from the other. For example, organizations can start with a VDI 2770-based document delivery and later scale up to iiRDS, where topic-based and interconnected information is provided in a context-sensitive manner. Thanks to the collaboration of the respective committees, the formats map well onto each other and share common ideas and similar goals. This is particularly beneficial for companies that are unsure which standard to adopt going forward, and it helps bring clarity to the landscape of formats. With a solid metadata foundation and appropriate software, it is already possible to generate both formats — or use hybrid packages for exchange.
The standards' specifications regarding formats and modeling can also serve as established best practices. This also neutralizes the adoption criterion — the question of how widely a standard is already used — that many companies rely on when evaluating standards. If the fundamental principles of sound information management (metadata, structure, and identification) are observed, the step toward an intelligent exchange format is not far off.
Closing Note
This article was published in a slightly modified form on May 19, 2020 in issue 03/20 of technische kommunikation.
Standards and Norms on the Topic
- DIN EN 61355-1:2009-03 "Classification and designation of documents for plants, systems and equipment – Part 1: Rules and classification tables" (VDE 0040-3:2009-03, IEC 61355-1:2008)
- DIN EN 62023:2012-08 "Structuring of technical information and documentation" (IEC 62023:2012)
- DIN EN 82045-2:2005-11 "Document management – Part 2: Metadata elements and information reference model" (IEC 82045-2:2004, VDE 0040-6:2012-08)
- iiRDS 1.0.1:2019-07 "tekom iiRDS Standard – intelligent information Request and Delivery Standard". Version 1.0.1. Release Date 12 July 2019. iirds.org
- VDI 2770-1:2020-04 "VDI 2770 Part 1 – Operation of process engineering plants – Minimum requirements for digital manufacturer information for the process industry – Fundamentals"
Further Reading on the Topic
- Erfle, Robert (2019): All Power to the Metadata. In: technische kommunikation, No. 1, pp. 41–47.
- Kreutzer, Martin / Parson, Ulrike (2018): Intelligent Delivery. In: technische kommunikation, No. 4, pp. 22–29.
- Oevermann, Jan (2019): Optimizing Semantic Information Access to Technical Documentation. tekom University Publications (Vol. 25).
