Terminology is the first critical point cited by practitioners when they are questioned on the need for standards. This paper gives a first analysis of maintenance terminology standards and highlights some discrepancies between the definitions and the meanings of the same terms. To standardize the meanings of the terms and to achieve the highest benefit of digital technologies in industry, a shared framework is needed. This paper questions the possibility of such a framework and the conditions of its benefit for industry.
Standards are critical for interoperability in maintenance. The benefit of a common terminology is obvious for all stakeholders and industrials outlined the need for improved semantic models. However, we have to face discrepancies in the terminology used in the different current standards. This problem is a general problem, which limits the interoperability of data.
We decided to join our efforts in the FORESEE cluster [
In chapter 1.3, we will focus on a few terms and their definitions, which seem to us important to share, because they are also used by other domains of engineering and highlights the need of clarification thanks to a shared framework,
In chapter 1.4, before our conclusion, we come back to the definitions of what we consider as basic terms of a shared framework based on Model Based Systems Engineering methods, and which should be appropriated by stakeholders, especially maintenance actors, to improve maintenance processes digitalization and pave the way to a consistent digital ecosystem including all the actors of the system lifecycle.
The standardization working group of the FORESEE [
535 terms have been listed, 68 terms among them have been selected in order to compare their definitions in the different standards. Comments can be made:
Among the selected core terms, some are specific to maintenance or to different maintenance sub-domains and other terms are more general to engineering, There are commonalities, with some definitions more precise in one standard, and also sometimes differences in the meanings of the same term.
A process needs to be defined and implemented to homogenize these definitions, beginning with the terms common to different engineering domains and following with the terms specific to sub-domains with a context dependent semantics.
It is important to analyze these differences also for operational reasons in the projects. For instance, the
UPTIME [
We will focus here on a few terms and their definitions either specific or not of the maintenance domain.
Non-specific terms are terms which are used in other engineering and manufacturing domains; the possible issues need to be addressed because advanced maintenance processes, as predictive maintenance, use data from various data bases as engineering, manufacturing, production, warehouse, even planning and cost data. Table 2 gives an extract for 4 terms of the analysis carried out for 68 terms. Extract of the definitions of terms from various maintenance standards with some first comments (Work In Progress to be completed by other sources of definitions)
These definitions show commonalities often due to convergence between two versions of the standards but also differences in the meanings. We will come back in the next chapter on the term system for instance.
We note also that expressions like "down state", "up state", "degraded state" are parts of the terminology without a definition of what is the generic term “state”.
At this stage, we make the following questions:
This task of terminology comparisons between reference standards is necessary as a first step to understand the semantics of a domain and to define a common terminology. It can be also a long and tedious activity; dispatching of the work is necessary between people sharing the same basic framework common to all the engineering lifecycle from design, where models are used to predict failures, to maintenance and even dismantling where historical data are needed for a proper recycling of parts or disposal of the waste.
Thus, in parallel to solving dissensus between experts of a specific domain, we think it will be helpful to build a necessary and sufficient framework with definitions and formalization of the common terms to the engineering domain. As system engineering is more and more deployed in industry to master the growing complexity of systems and as it is a common approach to all the domains, whatever the type of system, we think we have to focus on the basic terminology of system engineering.
System Engineering, with digitalization of engineering activities, is evolving to Model based system
engineering [
We have noted some issues in the definitions of the term “system” in the previously analyzed maintenance terminology standards.
In order to progress on a conceptual basis as solid as needed, we propose to remind some of the formal
definitions given by Mario Bunge in his works on the semantics and the ontology of systems [
Bunge’s ontology has also raised interest to structure information systems [
To give what we consider as the gist of the Bunge’s ontology, we list the basics of this ontology: A system is an object, which is made of interacting parts or sub-systems, and which is in interaction with its environment, There are concrete systems, natural or artificial ones; a simple machine is an example of an artificial concrete system,
Concrete systems are known through their physical properties of interest, and these properties are always changing, There are different types of properties, for instance essential properties, which are linked together by a law, and emergent properties when a system has properties which are not possessed by its sub-systems; concrete systems have physical properties and abstract systems have formal properties,
Patrice Micouin [
We can see the importance of properties and of formal structures to represent properties, constraints, events and knowledge in a digital ecosystem.
Properties of systems are represented as data and documents in information system: data sheet, databases, functional drawings, digital mock-ups thanks to symbolic systems, more or less standardized and common to a given discipline, used to make the link between the real world and its representation and to handover knowledge on the system.
UPTIME [
Standards are a source of terms with definitions to be analyzed and standardized before their formalization and their translation in a computing language. A shared framework will help the stakeholders from different disciplines and with different interests to cooperate consistently on a common system. System engineering principles, methods and tools seem to us the best candidate to build this shared framework.
Besides this shared ontological basis, ontologically consistent modules shall be edited by discipline experts. A further work shall address the governance of this set of modules and experiment the benefit of advanced technological standards to use a set of periodically updated ontological modules for contextualized use cases.
Maintenance, responsible for the highest “Up state” of a system, could be a prime activity to co-develop, complete, deploy and benefit of such a framework.
This research has been partially supported by the project “UPTIME – Unified PredicTIve MaintEnance system” (Grant Agreement n° 768634) (https://www.uptime-h2020.eu/) funded by the European Commission. 7. References