One of the oldest and still current definitions is that cited by the National BIM Standard-United States Project Committee (NBIMS-US) organization. As defined in the original NBIMS document, “BIM is a digital representation of the physical and functional characteristics of an object. As such, it serves as a common knowledge resource for information about an object, forming a reliable basis for decision-making throughout its life cycle, from inception.” [7]. This definition highlights three extremely important points. Firstly, in a BIM-led investment process, a “knowledge and information resource” is created. Thus, the resource being built is saturated with data, which, if appropriate, structured and delivered on time, becomes information. Information gives the necessary knowledge and knowledge gives wisdom (according to the almost century-old well-known DIKW scheme: data -> information -> knowledge -> wisdom). Secondly, it is the enumerated ‘wisdom’ that provides the basis for decision making, or at least reduces uncertainty and increases the understanding of a phenomenon. Thirdly, the exchanged resource should accompany the building object throughout its life cycle from the earliest conception to its potential demolition. During this cycle, the form and scope of the resource changes, but it inherently always accompanies the building object as its digital twin. All three aspects mentioned are still relevant and emphasized by many.

In the UK, the main definition of BIM is phrased a little differently, with an emphasis on process. The UK Task Group emphasizes that BIM is not a technology but a process. They define it as follows: “BIM is the process of designing, constructing and operating a building or infrastructure facility using object-oriented electronic information.” [8]. BS 8536-1:2015 is part of a suite of documents developed to support BIM at maturity level 2 (as per the Bew–Richards ramp), which is required for centrally funded public projects from April 2016. Level 2 BIM requires fully collaborative 3D BIM, with all project and asset information, documentation and data being electronic. The cited definition emphasizes the implementation of a process, which is made up of stages. Electronic information is used in each of these stages. The UK definition ignores the outcome of delivering a tangible product/service and, in a way, treats BIM as a tool to achieve the goal of delivering the investment. Undoubtedly, this definition raises the debate as to whether BIM is a technology, a process, a methodology or perhaps a bit of everything?

An interesting definition of BIM is cited by the well-known online BIM dictionary: “Building Information Modelling (BIM) is a set of technologies, processes and principles (standards) that enable multiple stakeholders to collaboratively design, build and operate a facility in a virtual space” [9]. The dictionary authors add that the term BIM has evolved over the years and is therefore best understood as an “expression of digital innovation” across the construction industry. Thus, the above definition notes that BIM uses techniques (technological advances), and that BIM is both a process (or a set of smaller processes) and uses a certain set of principles (usually by this mean methodology). The fusion of these three important aspects is used by stakeholders throughout the entire life cycle of a facility: from the design phase, through project implementation, operation and potential demolition. The phrase “virtual space” appears in the definition. This concept is broad enough that it seems safe even in the case of changes that are rapid and at times revolutionary in the development of BIM. Thus, not limited to three dimensions. In the glossary after the definition, it is noted that in the international standard ISO 19650 Part 1 BIM refers to “the use of a common digital representation of a built Asset to facilitate the design, construction and operation processes to provide a reliable basis for decision-making” [10]. Again, the need for a digital twin to function throughout the life cycle of a built asset is highlighted, which can facilitate decision making. The word “reliable” appears here, which further emphasizes and somewhat suggests the existence of advantages and benefits of using BIM.

A similar definition is cited by ISO 29481-1: 2016 Building Information Models—Information Delivery Manual—Part 1: Methodology and Format: “BIM is the use of a common digital representation of a building object (including buildings, bridges, roads, manufacturing plants, etc.) to facilitate design, construction and operation to provide a sound basis for decision-making.” [11]. In this definition, in addition to life cycle and knowledge, different types of building objects are mentioned, making people aware that BIM is not only about buildings. It should be clearly emphasized that BIM can apply to basically any space, not only buildings, but also assemblies/collections of such buildings, fragments of public spaces or entire settlements or cities. Any such restriction narrows the potential use and development of BIM.

The definitions listed above generally attempt to reduce BIM to a single understanding. The organization buildingSMART has taken a slightly different approach. It breaks the BIM acronym into three separate concepts and defines each of them separately. Developing BIM as a building information model is “understood as files (often in unique formats) that can be extracted, exchanged or combined to support decision-making about a building or other facility.” BIM developing as building information modeling is “a process involving the generation and management of digital representations of the physical and functional characteristics of a building.” Developing BIM as building information management is understood “as the organization and control of investment processes through the use of the parameters of a digital building model to exchange information about asset components throughout the investment cycle.” The synthesis of all of these three definitions, however, boils down to the same thing: a relational database accompanying a building object throughout its life cycle which can serve a variety of purposes (not just decision making). In many areas, not just AECO, the term is emerging as Better Information Management [12]. This expansion of the acronym BIM in turn shows the trend away from BIM towards IM itself. Information management itself is beginning to take center stage. And it does not matter whether it concerns a building, a structure, an infrastructure facility or a public space.

Whatever the definition, the BIM concept has its well-known assumptions. Current efforts to realize the BIM concept are still in the stages of development, as well as the use of the tools and techniques associated with it, and therefore concern selected elements of BIM and only realize part of the assumptions. Based on the literature review, the following target assumptions of the BIM concept can be formulated, the fulfilment of which will allow its full utilization:

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The building object model contains information in the form of data suitable for automatic processing;

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All of the information contained in the BIM model is true (the actual building is constructed in full compliance with the building model) and up-to-date (e.g., the building model is modified at the same time as a change is made to the building);

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The building model accompanies the building throughout its life cycle;

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The building model and its digital representation are independent of any specific software, and the software used is interoperable;

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The information contained in the BIM model is accessible (to an adequate extent) to all participants in the construction process, and the building object model functions as an area of cooperation between them;

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The elements of the BIM model contain information about their nature and behavior.

At this point, it should be emphasized, depending on the software used and the processes employed, that the BIM model may partially fail to meet the assumptions mentioned. Software has its limitations and processes often fail (they are too complex or not there at all). Software development has not kept pace with the dynamic development of BIM.

In conclusion, different organizations highlight different attributes of BIM. The graphic below distinguishes the six most frequently indicated. These can be divided into two groups: technical and organizational. Among the technical ones is the cited 3D model, which is built through semantic, often graphical databases and is a resource for information and therefore knowledge. Among the organizational attributes, it is emphasized that BIM is no longer just a technology, but a process and/or methodology used throughout the life cycle of an object of interest (Figure 1).