**1. Introduction**

Construction is a project-based industry [1] where stakeholders temporarily come together to complete one-off projects [2–6]. Construction projects encounter performancerelated challenges throughout asset management operations, final product quality, and stakeholder conflicts [7]. For instance, a subcontractor typically has no direct obligations to anyone other than the main contractor [2]. Therefore, the construction industry has become less trustworthy with more adversarial relationships, which is considered an obstacle to industry performance and innovation [1,8]. Adopting digitalized and smart solution tools will assist in resolving performance issues and contribute to the success of construction projects by increasing industry productivity [9]. However, Mason and Escott [10] stated that transitioning to the smart construction industry still has a path full of challenges due to the traditional procurement mindsets and lack of mature/trusted methodology to enable this. Perera, Ingirige [11] stated that the efficiency of the data workflow and the ability of stakeholders to have a transparent data exchange are critical factors in enabling information and communications technology (ICT) in the construction supply chain (CSC).

Building Information Modeling (BIM) is widely acknowledged as the primary driver of the industry's digital transformation [12,13]. There have been previous studies that used BIM in the CSC to accomplish integrated information delivery all the way through

**Citation:** Hijazi, A.A.; Perera, S.; Alashwal, A.M.; Calheiros, R.N. Developing a BIM Single Source of Truth Prototype Using Blockchain Technology. *Buildings* **2023**, *13*, 91. https://doi.org/10.3390/ buildings13010091

Academic Editor: Muhammad Shafique

Received: 28 November 2022 Revised: 23 December 2022 Accepted: 26 December 2022 Published: 30 December 2022

**Copyright:** © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

the project's life cycle [3,9,14,15]. Globally, BIM plays a crucial role in facilitating the digitalization of design and related workflow in the construction industry [14–17]. Through BIM coordination tools and collaboration processes, CSC stakeholders are better informed of one another's activities [18]. There are still several obstacles to the widespread use of BIM in supply chain operations, including the construction industry's inherent complexities, a lack of openness, adversarial relationships, fragmented data, and disputes among players [2–5,8,13,14,19,20]. Because "*Construction Operation Building Information Exchange*" (COBie) data is maintained centrally by a single actor, disagreements arise across CSC parties and prevent BIM from being a legally recognized delivery model [4,8,15,19]. Furthermore, BIM tools cannot generate digital proofs for various transactions [21]. In addition, traceability issues and the inability of BIM to contain all project compliance and product data are also among the limitations of BIM [14]. Deng, Ren [22] emphasized that any future framework for the CSC's BIM integration must include trust as a prerequisite for effective communication between project stakeholders. Consequently, any future CSC research should take reliable data exchange into account.

Blockchain technology has been heralded as revolutionary [4,23–25] and is set to upend many facets of enterprises that rely on coordinating information and trust to allow a trustworthy database architecture with multiple control entities [26,27]. Blockchain is a type of distributed ledger technology, which securely records information in cryptographically sealed blocks replicated across a peer-to-peer network [14,27,28]. Due to its tamper-resistant properties and suitability for data auditability and transparency, blockchain is being recognized by a growing number of sectors as a key innovation with a trusted data exchange platform [14,27,29]. However, according to "*Australia's Department of Industry, Science, Energy, and Resources National Blockchain Roadmap*", the construction industry is lagging behind other industries in terms of the proportion of business activities involving blockchain technology [30]. For the design and development phases of a BIM model, existing academic studies have validated the authoring copyright, but not the ownership of CSC product data or the supply and manufacturer data node (*which includes production data, compliance data, reliability data, maintenance, and warranty*) [21,31,32]. Due to poor CSC data quality and reliability, the advancement of BIM implementation for operations may not produce the desired results for its higher levels of digitalization [8,12,19,33], as it is not possible to act on a digital asset that cannot be trusted [33].

This study aims to create a prototype proof of concept for integrating blockchain and BIM for construction supply chain data delivery. The software prototype presented in this paper helps establish the technological feasibility of a single source of truth model for integrating blockchain technology and BIM. The concept of a single source of truth model was borrowed from the ICT sector [34]. The "*single source of truth*" is defined as an "*authoritative source of its data that offers data services to other entities while ensuring that business entity decisions are based on the same datasets*" [34–36]. This paper demonstrates a step-by-step methodology starting from understanding the current business scenario and proposing logical system architecture, followed by selecting a blockchain technology platform, designing system architecture related to technologies, prototyping, and evaluating it through a virtual business scenario. The process stated by Qing and Yu-Liu [37] detailing the development of software prototypes was used in this research for developing a software prototype. The scope of this paper is limited to the delivery of CSC data in preparation for handover and operation. Because it does not influence the supplier and manufacturer data node for the handover stage, Building Information Modeling (BIM) for the design stage, which is where the process is centered on BIM 3D model authoring, is excluded.

The paper is structured as follows. First, the authors conduct an in-depth analysis of the current situation of BIM and blockchain integration to investigate how blockchain technology might be used to solve the issues faced by the CSC (Section 2). Then, the authors introduce the research method, design, and tools for the BIM single source of truth prototype model development using blockchain technology (Section 3). Next, the paper presents step-by-step software prototype development and how it was comprehensively evaluated to ensure the accurate execution of the smart contract using a virtual business scenario that included external validation (Section 4). Following that, the discussion is presented, including practical implications, managerial insights, limitations of this study, and future research directions (Section 5). Finally, the authors present the conclusions and contributions of this study (Section 6).

#### **2. Literature Review**

Though there is no longer any debate about the importance of integrating blockchain technology with BIM, there is still a lack of academic literature on its proof of concept [38–41]. By demonstrating the reliability of the construction supply chain data across all supply chain actors, the integration of blockchain technology and BIM has the potential to alter the definition of BIM supply chain data delivery for facility management from information-centered 3D modeling based on coordination tools to a trusted data exchange model based on a reliable workflow [3,36,42]. However, most academic literature has used hypothetical cases to support this integration, with a significant gap in software prototype approaches [43]. Future works are recommended to demonstrate a step-by-step methodology of integrating BIM and blockchain technology to help various practical scenarios, given that BIM is the best route to implement any emerging technology in the construction industry [28,44,45]. Perera, Hijazi [28] presented a step-by-step methodology for implementing a blockchain in a built environment, which helps to provide the foundation for developing technological feasibility of proofs of concept relevant to land registry transactions; however, the proposed model does not deal with supply chain data. The proposed model [28] could result in introducing blockchain to solve transparency challenges in some built environment applications. Still, data source affects adoption, and this is where BIM needs to be in action with blockchain to create reliable supply chain data [27,35]. Regarding this, Li and Kassem [46] stated that the construction industry is not yet sufficiently digitized to fully benefit from blockchain technology. Due to this, there is still a lack of maturity in the use of blockchain technology with BIM for supply chain data delivery [14,47–49].

Current academic literature focuses primarily on how this integration may occur, presenting blockchain as a new technological tool only for aiding transparent transactions for BIM 3D modeling files in the form of "*project-centric*" 3D modeling files [32,46,50]. Celik, Petri [51] proposed a blockchain technology-based BIM model; it integrates by saving the IFC (Industry Foundation Classes) file hash code (a BIM file) and its action using smart contracts. However, this integration approach drastically restricts the utilization of blockchain technology's potential for value transfer in the form of a digital ecosystem of connected databases with multiple control entities; it also isolates BIM delivery in siloed electronic files, such as Revit files [8]. Revit is one of part of the BIM software that includes 3D modeling graphical and non-graphical information to enable the project delivery through coordination by avoiding gaps and overlap in team members' work utilizing an electronic file-based model [52]. The integration needs to ensure an ecosystem of linked databases within the blockchain technology (a decentralized database) to be connected, not isolated, to BIM (a centralized database) [36,50]. This results in the advancement of BIM delivery toward machine-readable datasets "*enabling an ecosystem of connected databases based on consistently organised dataset*s", as viable solutions for the automation of operations and facilities management [12,53]. A recent study by Hijazi, Perera [36] provided the data model for integrating BIM with blockchain technology to help construct organized and trustworthy datasets for BIM supply chain data delivery; nevertheless, the study does not illustrate in-depth validation of the suggested model and its technological feasibility. In the industrial scenario, "*BIMCHAIN*" was developed by a French startup that presents a solution for integrating blockchain technology capabilities with BIM [21,35]. It intends to generate digital evidence of different BIM transactions. However, the blockchain technology in this scenario only keeps a hash of the digital Revit file's alteration record, not the actual data update, which means a single party (the model authoring stakeholder) is responsible for reconciling diverse BIM transactions. Thus, this solution might validate the 3D BIM model authoring

file copyright for the design delivery [21], or ensure a confidentiality-minded framework between the project members in case of a sensitive BIM design collaboration model [54], but not the ownership for the supply chain product data where there are multiple control entities in the 3D BIM model during the handover phase [8]. Copyright is only one type of intellectual property (IP) protection; the contract could ensure it as it comes under the responsibility definition, such as the case of the Construction Industry Council (CIC) BIM protocol, which detailed how the BIM model and objects should be created, and where BIM delivery is still struggling to be reliable by ensuring the ownership of the supply chain product data [36,55].

A blockchain platform is one of the most secure database platforms because it is a decentralized and distributed database, and its data is immutable [3,46,56]. Therefore, the blocks (i.e., transactions) within a blockchain platform are copied across numerous computers, ensuring that the data contents of each block cannot be modified. Moreover, the algorithm can verify and validate the block's proof-of-work by itself [23]. In contrast, Coyne and Onabolu [57] stated that the blockchain struggles to overcome the privacy issue. There are different blockchain platforms available. "*Ethereum*" is the first public blockchain platform to allow smart contracts for general consumption, and it is now utilized mostly by the financial industry [29,50,54,58–60]; however, it is not appropriate for many types of businesses, such as the construction industry, where data privacy is crucial [28,50]. Thus, the blockchain should guarantee the veracity and accessibility of information while protecting its confidentiality [3,45,61]. Privacy and identity management methods have and will continue to have a substantial influence on business blockchain development [62]. Thus, the "*FIBREE*" blockchain industry report [63] strongly recommended "Hyperledger Fabric" as a blockchain platform with private permissions to meet the privacy requirements for a broad range of industry use cases, including data transactions in the construction industry [60,64]. Multiple software development kits based on modular and pluggable components [50,64] are provided by Hyperledger Fabric to accommodate varied applications and ease participant buy-in [60]. Section 3 explains why Hyperledger Fabric blockchain technology was selected as the best platform for constructing a system prototype that integrates BIM and blockchain technology.

A smart contract can be programmed to process a self-executing contract by translating the rules from the terms of the agreement into lines of code using a "*Generalized Adaptive Framework*" (GAF) [65] for a neutral data standard, such as the "*International Foundation Class*" (IFC). This allows for the automation of code verification procedures for routing data that must be stored in the blockchain network. The suggested GAF concept for automated processes entails the construction of a computable representation of predefined laws, as well as means for transferring data between the framework's various components (blockchain network) and BIM data [66]. A further approach might be a smart contract that secures the enforceability of transparency by executing the CSC data, thus making the CSC data immutable and accurate. The prototype proposed in this article implemented the second alternative by directly linking CSC data from external entities to a blockchain network and implementing transactions on top of a blockchain ledger using a smart contract solution. The section that follows describes, in detail, the methodologies used to illustrate the technical viability of a single source of truth approach for integrating BIM with blockchain technology.

#### **3. Research Method, Design, and Tools**

The development process of the software prototype follows the procedure stated by Qing and Yu-Liu [37] for the development of software prototypes. Several other researchers, such as Perera, Hijazi [28], Xue and Lu [67], and Ahmadisheykhsarmast and Sonmez [68], working on blockchain at the application layer, have also used similar developmental steps. Thus, we designed the development process of the BIM single source of truth prototype using blockchain by performing the following steps: understand the current business scenario and propose logical system architecture, select the blockchain platform, design

the physical system architecture related to technologies, and develop the prototype and evaluate it, as illustrated in Figure 1 and described below.

**Figure 1.** The development process of the BIM single source of truth prototype using blockchain technology.

To understand the current business scenario, the data flow diagram (DFD) was used to structurally identify the existing process of the BIM construction supply chain data delivery by describing data flows of a system at various detail levels and propositioning logic models that express data transformation in a system [36,37,69,70]. The information delivery for the current business scenario is set up to work in line with the "*Common Data Environment* (CDE)" workflow, which was outlined in "*ISO-19650 Part 1, Section 12*", and "*BIM maturity Level 2*" deliverables adhere to the guidelines of the "*PAS 1192-2-2013*". The current business scenario is described in Section 4.1 and the proposed system overview for the logical system architecture, independent of technology is elaborated in Section 4.2.

The "*Simple Multi-Attribute Rating Technique*" (SMART), which is a common tool for assisting in correct decision-making to solve a problem and find the best solution [71], was used to rank and identify the most suited blockchain platform among the identified platforms. Permissioned networks were chosen as the best sort of blockchain for CSC data transactions because stakeholders should be identified and held responsible for their conduct. For CSC activities, the blockchain database for a project contains sensitive information that organizations intend to keep private, such as commercial information [72]. As a result, the list of candidates with blockchain platforms included *Corda R3* [73], *Elements* [74], *Hyperledger Fabric* [75], *IBM Blockchain* [76], and *NEM* [77]. The Hyperledger Fabric blockchain platform was chosen as the best fit for the defined needs since it obtained the greatest value. In its design and implementation, the Hyperledger Fabric architecture provides great levels of flexibility and secrecy, making it applicable in a wide range of environment applications [25,50,78,79]. It aids in attaining privacy since it needs permission to read and write through the permission model, which is characterized by the capacity to modify the state of the ledger community [79].

By separating transaction processing into three steps, the Hyperledger Fabric design provides auditability. Phase one: utilizing distributed logic processing via Chaincode services to create a smart contract, which is the business logic code of a transaction on the Hyperledger Fabric platform; phase two: utilizing transaction ordering via consensus services to create blocks of transactions and facilitate network trust; and phase three: transaction validation via membership services [50,80,81]. The outputs of the selection of a blockchain platform, *the Hyperledger Fabric*, directly contributed to the system architecture (Section 4.3). This step includes designing the physical system architecture, identifying the technology that will be used, and determining where the described system processes used Hyperledger Fabric terminology. According to the process flow stated by Qing and Yu-Liu [37], the next step in developing system architecture is validation by developing a system prototype including the "*process sequence*", which is a process planning of a successful transaction within the system prototype for integrating BIM, blockchain, and Chaincode (smart contract) development, as explained in Section 4.4.

Finally, the software prototype was comprehensively evaluated to ensure the accurate execution of the smart contract using a virtual business scenario that included external validation. The attributes of the virtual business scenario were set to conduct the test run. Cladding attributes, as a sample of the CSC data delivery, were considered the CSC element to execute the smart contract. The cladding has become an incandescent topic of attention in several countries as an example of a CSC object that is not considered a "structural" part of the building [82], but it could cause a threat to the safety of the residences during the operation phase [83], such as what happened at the Grenfell Tower (London), which led to an unprecedented loss of life [84,85], and the fire incidents at the Lacrosse Apartment Building (Melbourne) and the Torch Tower (Dubai), which led to unavoidable multimillion-dollar bills for property owners [83]. Even when several ad-hoc actions have been implemented to combat non-compliant cladding products, the Australasian Procurement and Construction Council mentioned that more than 50% of cladding products might still be non-compliant, with the majority of stakeholders completely unaware of the financial burden it could present [83,86]. Keeping the preceding discussion in mind, cladding was deemed an excellent example for the virtual business scenario to help introduce a BIM single source of truth prototype using blockchain. The external entity's (supplier) role was performed by the researchers, whereas the main contractor's role was performed by a participant organisation. The protocol for the virtual business scenario, selection criteria, data collection, data analysis, and the test case and its results are explained in detail in Section 4.5.

#### **4. Develop, Validate, and Test the Proof of Concept**

*4.1. The Current Business Scenario*

In the main process of the current BIM supply chain data flow, the BIM model is developed during a project's construction phase in response to requirements set out in the "Employer's Information Requirements" (EIR) to work in line with the Common Data Environment workflow, which is outlined in "ISO-19650 Part 1, Section 12", and "BIM maturity Level 2" deliverables adhere to the guidelines of the "PAS 1192-2-2013 specification for information management for the capital/delivery phase of construction projects using building information modelling". In this process, suppliers are required to prepare an IFC file for the product data (CSC element) to be sent to a subcontractor or consultant (the author of the IFC BIM model). The "BIM execution plan" (BEP) then details how the 3D BIM model is to be delivered to the client through the main contractor in order to fulfill the client's asset information demands (AIR). In the construction phase, the "responsible" party is the main contractor, who is in charge of coordinating the transfer of the federated 3D BIM model used to create the "asset information model" (AIM). This process is decomposed into three main subprocesses. The first subprocess (Process 1.0) is to acquire CSC data. Each task team is required to send the IFC model data to the main contractor through the CDE. This subprocess will create considerable ambiguity about the ownership and authoring liability of the IFC data between the suppliers, subcontractors, and the main contractor for the CSC elements and/or model. The second subprocess (Process 2.0) is to review the CSC data provided by the main contractor and share it with other appropriate task teams or delivery teams or with the appointing party. In this subprocess, the main contractor is responsible for managing the construction phase's workflow and for transferring the federated BIM model to generate the AIM. As they are not responsible for the model components, there is a benefit in preserving an immutable record of where the CSC model elements were obtained. The federated BIM model must reflect the facility as built and be enhanced with CSC data (as defined in the EIR) before being "published" as the third subprocess (Process 3.0). In this subprocess, the AIM is derived through a combination of federated BIM model deliverables and COBie datasheets, all of which are underpinned by Uniclass 2015. As mentioned in Section 2, BIM is yet to be considered a reliable delivery model, as the COBie data are "centrally stored" by a single actor [3,4,10,15]. In this scenario, the main contractor has three subprocesses for acquiring the CSCs that were developed by their originator or task team (consultants, subcontractors, or suppliers). Process 1.1 will be decomposed into three child diagrams (subprocesses), Process 1.2 will be decomposed into six child diagrams, and Process 1.3 will be decomposed into six child diagrams, as illustrated in Figure 2. The decomposition involves the top-down development of a DFD to reduce the complexity of the system [37]. This will help to provide a clear picture of the existing information delivery system (existing work packages) and create a functional process network for developing the proposed model. It will also demonstrate the relationship between the CSC stakeholders and how the function of reconciling different data is still usually undertaken by one or a limited number of parties. This is a key point in understanding how the proposed solution needs to be adapted to the existing work packages. However, analyzing information delivery for more than one CSC element to aid in the understanding of the existing information delivery system would be redundant, as all elements have the same work package. A single CSC element can be used to mimic the current data flow.

**Figure 2.** The data flow diagram (DFD) for BIM construction supply chain data delivery.
