Visualization of blockchain-based smart contracts for
delivery, acceptance, and payment process using BIM
X Ye1*, N Zeng2 and M König1
1 Chair of Computing in Engineering, Department of Civil and Environmental Engineering,
Ruhr-University Bochum, Germany
2 Department of Construction Management and Real Estate, School of Civil Engineering,
Southeast University, China
*Corresponding author e-mail: email@example.com
Abstract. Building Information Modeling (BIM) provides an excellent opportunity to digitally
document and visually display construction projects’ information throughout their whole
lifecycle. Another recent technology that is fostering the digital transformation of the
construction sector is blockchain-based smart contracts. In combination with BIM models,
such smart contracts can be used for the automation of delivery, acceptance, and payment
(DAP) processes in the construction industry. The DAP process can be modelled by using
smart contracts and securely stored via a blockchain. Since smart contracts are programming
codes, for stakeholders it is difficult to understand what is exactly written in the smart
contracts. Therefore, it is necessary to visualize the status of the deployed smart contracts and
the executed transactions. In this paper, a framework is highlighted to record and visualize the
status of the DAP processes by combining BIM with smart contracts using the Business
Process Model and Notation (BPMN) to develop a smart contract system. With the help of
suitable visualization concepts, the individual transactions of the blockchain can be displayed
in a comprehensible way. The feasibility of the framework is presented through an illustrative
implementation of the smart contract system. The proposed framework can help project
participants better understand the current state of a smart contract.
Keywords: BIM, smart contracts, blockchain, process automation, smart contract visualization
The visualization of building structures based on Building Information Modeling (BIM) has become
increasingly important in the architecture, engineering, and construction (AEC) industry and is
considered one of the most important areas of information and communication technology (ICT).
Newer visualization paradigms or technologies such as virtual reality (VR), augmented reality (AR)
and mixed reality (MR), or the animation of simulations of construction work are becoming more
common as well [8, 11]. Compared to construction products and processes, the visualization and
automation of business processes in construction projects has not gained enough attention.
The construction delivery, acceptance, and payment (DAP) process plays an important role in the
construction project management, which involves key project stakeholders, e.g., the client, the main
contractor, subcontractors, and related suppliers. The modeled DAP processes can be automated and
made more secure by representing them as smart contracts [4, 12]. However, the visualization of the
underlying process sequence of smart contracts is rarely explored. It leads to a lack of understanding
and control over the automated DAP process, and hence disputes or conflicts may occur. The Business
Process Model and Notation (BPMN) is an established process modelling method for the formal
description and visualization of business processes. It is also widely applied for the modeling of
various processes in the construction industry  To enhance the process visualization, BIM can
provide a multi-dimensional built environment, and BPMN can provide specified DAP process
models. The combination of BIM, BPMN, smart contracts and blockchain can thus lead to a better
representation of the DAP process and support project management.
This paper aims to provide an approach for visualizing the real-time DAP process using BIM,
smart contracts and blockchain. For visualization, the BIM model is connected to the smart contracts
based on the blockchain to visualize the individual states of the DAP process for each building
element in real-time. Our approach is presented through a smart contract system design and an
implementation with a real-world example.
2. Literature Review
Product visualization and process visualization are two distinct aspects of construction visualization
[8, 10, 11]. For product visualization, three-dimensional (3D) parametric modeling of building
products has been developed incrementally over four decades . BIM has been widely applied as a
result of this evolutionary process. Construction process visualization is generally divided into two
categories, i.e., activity level visualization and operation level visualization [8, 10]. Graphical 3D
models can serve as an effective communication method at both levels. Further 3D building models
are “animated” by linking them to construction schedules to provide the fourth dimension, so-called
4D BIM .
Visualization of construction processes, progress, deviations, etc. by means of 4D BIM is well
researched [3, 19]. Some systems incorporate cost as a “fifth dimension” (5D) of project information
and aim to generate the bill of quantities (BOQ) and manage payments . However, there are no
explicit steps to formalize and track the complete process between the contracting and the payment of
the services in the construction industry. This process involves at least two parties, namely the payer
(the client) and the payee (the contractor), and comprises three main steps - delivery, acceptance, and
payment, therefore referred to as the DAP process. Compared to the construction process (i.e.,
operations), the DAP process is fundamentally different, and the visualization of the DAP process is
For an efficient construction DAP process management, as-designed information (e.g., the BIM
model), as-built information (e.g., 3D point cloud models) and as-paid information (e.g., transaction
records) are crucial. The interactions and information exchanges between the client and the contractor
are essential for DAP process execution. Therefore, process modeling methods, which consider
information exchange among multiple participants, such as BPMN, are appropriate for DAP process
visualization. Cheng et al.  used BPMN to model and visualize the construction supply chain.
Häußler et al.  conducted code compliance checking of railway designs by integrating BIM and
BPMN. Linking BPMN process maps of contracting and paying with the BIM model can contribute to
a BIM-enabled payment visualization.
With the development of digital transformation in the construction industry, the adoption of smart
contracts is becoming more frequent. Smart contracts serve as programmable applications to write,
verify and enforce transaction conditions automatically. Smart contract was first proposed by Szabo
and it was defined as “a computerized transaction protocol that executes the terms of a contract” .
Later the definition of smart contract was updated as “a set of promises, specified in digital form,
including protocols within which the parties perform on these promises.” . Currently, smart
contracts serve as general-purpose programmable applications on blockchain platforms to write, verify
and enforce transaction conditions. In the construction field, a series of smart contract-enabled
applications were developed for DAP process automation [4, 12]. However, smart contract
visualization is rarely explored, let alone the visualization of the smart contract-enabled DAP process.
Jeong and Ahn  designed a framework for creating Ricardian contracts and visualized the mobile
User Interface (UI) and the User Experience (UX) of smart contracts. In their study, the contents of the
existing smart contracts were embedded in the block through byte code and then became a style sheet
document through the binding process or the verification process by the app. It was then automatically
converted to HTML or PDF through templates and data bindings for the visualization of the smart
contract. However, their research did not address the DAP process in construction. How to visualize
smart contracts in the context of construction DAP is an open issue that deserves further investigation.
3. Research Methodology
In this paper, a concept for the visualization of smart contracts with application in the DAP process is
proposed. The methodology is divided into two parts. The first part introduces the overall framework
of visualization of smart contracts for the construction DAP process. The second part clarifies the
execution workflows of the designed smart contract system from loading the BIM model to displaying
the DAP process and the corresponding blockchain transactions.
3.1. Smart contract visualization
The framework for smart contract visualization is shown in Figure 1. Three components are
distinguished, namely BIM data generation (Figure 1a), smart contract generation (Figure 1b), and
smart contract visualization (Figure 1c). This paper focuses on the concept of visualization.
BIM data generation: The BIM model, the corresponding bill of quantities, and related
construction schedule can provide essential information for a construction section or project. These
three files are used to create a billing plan that links construction work items to scheduled completion
dates, quantities, and payment information. All work that can be billed together at one time forms a
billing unit (BU) in the billing plan. All information respectively files for a contract will be provided
as an information container for the linked document delivery (ICDD) and are the basis for the
visualization of the smart contract. The generation of the billing plan and the ICDD has been done by
developing a billing model setup tool, which is explained in previous work .
Smart contract generation: Appropriate generation concepts have been developed for generating
the processing logic of a smart contract. Initially, clients and contractors design the smart contract
Figure 1. The framework of a) BIM data generation (left-upper), b) smart contract generation
(left-bottom), and c) smart contract visualization (right)and c) smart contract visualization
logic using BPMN. The behavior of each activity in BPMN is defined as “Action” in the smart
contract generation procedure. Each BPMN activity should declare only one “Action”. There are
different types of actions, e.g. "view", "modify" and "pay". With the help of "view", it is possible to
indicate that a BPMN activity only displays certain information, such as the start date of the event.
The "pay" type is used to trigger an automated payment action with a specified payment amount from
one user address to another user address. The smart contract logic based on BPMN can be
automatically translated into a smart contract via a smart contract generator . The generated smart
contracts are written in high-level programming languages, such as Solidity from Ethereum. In
conclusion, the smart contract generation procedure provides the smart contract logic file in BPMN
format as an input of the smart contract system as well as the generated smart contracts for later
execution and visualization.
Smart contract visualization: The ICDD extracted files (i.e., the BIM model and the billing plan)
are used to provide the geometry, quantities, and payment information of the smart contract system.
The smart contract logic (BPMN) and the generated smart contracts are for establishing and
visualizing DAP processes. Each generated smart contract is compiled into bytecode and an
Application Binary Interface (ABI). A bytecode of a smart contract is a long string that only contains
numbers and letters in a specific order. The bytecode will be deployed in the blockchain so that the
blockchain can execute the smart contract code. An ABI of a smart contract is an interface represented
system and the smart contracts deployed in the blockchain network. The ABI is deployed in the smart
contract system to show the callable functions of the deployed smart contracts and connects the smart
contract system with the blockchain network. The interaction (i.e. messaging and signing) between the
blockchain network and the smart contract system is realized with the help of the bytecode and the
ABI. The configuration files (i.e. the payment configuration and the progress entries) are essential
information for the implementation of the DAP processes. A common data environment (CDE) is used
as off-chain storage, namely a database outside of the blockchain. The ICDD, configuration files, the
smart contract logic (BPMN) file, and the smart contracts will be stored in this CDE and their
corresponding hash values will be stored in the blockchain.
In the smart contract system, the BIM model and the billing plan are linked together based on the
GUIDs of the BIM elements stored in both files to provide the building geometry, quantities, and
payment information at the same time. Each BU of the billing plan could have a DAP process that is
different from other BUs’ based on the actual situation of the construction project. By connecting each
BU with its specified DAP process, real-time DAP process information of each building element could
be displayed. Each activity of the DAP process diagram is a DAP process status, and the procedure
from one activity to another activity is defined as a DAP process status change. Each DAP process is
deployed as smart contract codes in the blockchain and its BPMN diagram is linked with the ABI to
provide the real-time DAP process status stored in the blockchain. Each status change of a DAP
process will generate a blockchain transaction and these blockchain transactions will be displayed in
the smart contract system. The design of the smart contract system for smart contract visualization will
be further explained in the following section.
3.2. Smart contract system execution workflow
To design a smart contract system for visualization, the functions of this system should be clarified.
The user-system interactions and operations of the smart contract system are shown in Figure 2, which
display the fundamental logic of the smart contract system. This logic can be divided into user
operations (Figure 2a) and system operations (Figure 2b), where the system operates according to the
user operations. This execution workflow aims to provide the main logic of the system execution and
the interaction logic of the four main components (i.e., the BIM model, the billing plan, the DAP
processes, and the blockchain transactions) of the smart contract system.
When the user selects one or multiple BUs, the linked BIM elements will be highlighted. Similarly,
when the user selects one or multiple BIM elements, all the linked BUs will also be highlighted. For
these selected BUs, a suitable DAP process can be assigned by the user based on the project need.
After the assignment, the system will activate the corresponding smart contract codes and record the
connection of the selected BUs and the DAP process in the blockchain. This record will be stored as a
blockchain transaction and displayed in the smart contract system. The DAP process of each BU can
be changed based on the actual construction progress. When the DAP process of some BUs has been
changed on the construction site, the stakeholder can select these BUs in the system and modify their
current DAP process status. In this way, the system will modify the status via the deployed smart
contracts. If successful, the new DAP process status will be highlighted in the BPMN diagram of the
system. Meanwhile, these status changes will be stored in the blockchain and displayed as blockchain
transactions in the smart contract system.
4. Illustrative implementation
4.1. Implementation workflow
A workflow for implementing the smart contract system is shown in Figure 3, which provides an
implementation solution for illustrating a construction DAP process example based on the proposed
smart contract system. The illustrative implementation steps are realized based on Hardhat, React,
xBIM, BPMN.io, and Etherscan, which can be grouped into four steps, namely system creation, front-
end realization, back-end realization, and smart contract deployment.
In the system creation step, a Hardhat project is first created to use the Ethereum network, where
Hardhat is a development environment to compile, test, and debug Ethereum software . A React
front-end is then created within the Hardhat project to form a smart contract system, where React is a
React front-end can be realized. In this front-end realization step, a BIM viewer, a billing plan table, a
BPMN viewer, and the linking rule between the BIM model and the billing plan are implemented. The
BIM viewer is implemented via xBIM, where the xBIM provides an open-source software
development tool that allows users to read, create and view BIM in the Industry Foundation Classes
(IFC) format. The BPMN viewer is implemented via BPMN.io, where BPMN.io provides a web-based
BPMN viewer and editor to read and display BPMN 2.0 diagrams.
Figure 2. The execution workflow of the smart contract system explained via
user-system interactions and operations with a) user operations (upper) and b)
system operations (bottom)
The whole smart contract system can then be further realized by coding the functions connecting
the front-end to the blockchain as a back-end realization step. In this step, the linking rule between the
smart contract ABI file and the loaded BPMN is first coded. The user interaction with the highlighted
BIM element function as introduced in Section 3.2 is then realized to modify the DAP process real-
time status data stored in the blockchain for each billing unit of the billing plan. The corresponding
blockchain transactions can be displayed in the front-end by connecting with Etherscan, where
Etherscan is a block explorer of the Ethereum blockchain providing equitable access to blockchain
After implementing all the functions for the system, the final step is to deploy the smart contracts.
In this step, the generated smart contracts from a corresponding BPMN file via the smart contract
generator are put into the “contracts” folder of the smart contract system. By executing this smart
contract system, the corresponding ABI file of the generated smart contracts will be created. If the
system is successfully executed, the implementation workflow is finished. This smart contract
deployment step is further explained in the following section.
4.2. Smart contract deployment
The DAP process of a billing unit (BU) is used to introduce the illustrative implementation, where a
BU stores the quantities and payment information for a group of construction works. This process was
defined in the previous work  and shown in Figure 4.
In this example, two roles (that of contractor and client) and eight tasks of the DAP process are
defined. The contractor first indicates the start of a specific BU. After finishing, (s)he indicates the
completion of this BU. The completion message will be sent to the client, who can then inspect the BU
for defects at the construction site. If no defect is detected, the BU can be automatically paid and the
entire BU process ends. If there are some defects, the BU will be divided into a completed-without-
defect part (BU.C) and a defective part (BU.D), of which the BU.C part is automatically paid and the
BU.D part is requested to be repaired. After the BU.D is repaired by the contractor, the client needs to
check the repaired BU.D and determine if the part is still defective. If so, the BU.D will be requested
again for repairs. Otherwise, the BU.D part will be paid automatically, and the entire DAP process for
that BU will end.
Figure 3. An implementation logic workflow for the smart contract system
The BPMN file within the process explained above (Figure 4) is loaded into a smart contract
generator for generating the corresponding smart contracts. As explained in the previous section, these
generated smart contracts are put into the “contracts” folder of the smart contract system. After
executing this smart contract system, the executed project is shown in Figure 5, where its folder
structure is displayed on the left, and some parts of a generated smart contract (i.e., SCExample.sol)
are presented on the right. For further details of the generated smart contracts, refer to Ye and König
As shown in the folder structure, this smart contract system is named “Hardhat_React_DApp”
(Figure 5a), which contains a “contracts” folder (Figure 5b) and a “frontend” folder (Figure 5c). The
Figure 4. A BPMN example for a BU's DAP process
Figure 5. The folder structure (left) and a part of the generated smart
contract (right, SCExample.sol) of the smart contract system after smart
generated smart contracts (i.e., SCExample.sol and SCProcessFlow.sol files) were put into the
“contracts” folder (Figure 5b), and its corresponding ABI (i.e. SCExample.json file) was generated in
the “contracts” (Figure 5e) of the “frontend” folder after executing the smart contract system. The
“app” folder (Figure 5d) contains the functions explained in the “Front-end realization” and “Back-end
realization” steps of the previous section.
4.3. The user interface of the smart contract system
After implementation, the resulting User Interface (UI) of the designed smart contract system is shown
in Figure 6. This UI can be divided into four frames: a) BIM model, b) Billing plan, c) DAP process
(BPMN), and d) Blockchain transactions. The BIM model (Figure 6a) is used to provide GUIDs and
the 3D visualization of the construction project. The billing plan (Figure 6b) is used to provide
corresponding quantities and payment information based on this BIM model. After loading the BIM
model in the IFC format and the corresponding billing plan in the XML format, their linkage will be
automatically checked in the system. If the checking succeeds, the linkage between the BIM model
and the billing plan will be established. In this way, a billing unit will be highlighted when its
corresponding BIM element is selected, and vice versa.
The DAP process shown as a BPMN diagram (Figure 6c) is used to display the real-time status of
the DAP process for each BIM element. The real-time status and its historical status changes are
stored in the blockchain using the GUID and the used DAP process identifier of the BIM element as
the key. By selecting either a BIM element (highlighted in yellow of Figure 6a) or a billing unit item
(highlighted in gray of Figure 6b), its corresponding DAP process will be displayed and its current
status will be highlighted in green (see Figure 6c). By interacting with a highlighted billing unit, the
corresponding menu item will be displayed and its current DAP process status can be changed. The
change has to follow the process flow of the DAP. For example, after a BU is started, the BU could
only be set as completed by the contractor. Each modification of the DAP process status generates a
blockchain transaction, which is displayed in Figure 6d.
Figure 6. The user interface of the illustrative implementation of smart contract system
5. Conclusions and further research
The interactions and information exchange between project participants are essential for DAP process
execution, and they can be arranged in smart contracts. Although smart contracts can improve the
automation of business processes in construction projects, the actual execution is not visible for the
construction participants. To better understand and monitor the process status and support interactions,
visualization of smart contracts is essential. This paper proposes a framework consisting of BIM data
generation, smart contract generation, and smart contract visualization. The main focus of this paper is
the smart contract visualization realized through the smart contract system design. The execution
workflows of the smart contract system are introduced by explaining the logic of user-system
interactions and system operations. An illustrative implementation is provided for the designed smart
contract as a possible solution for the proposed framework, in which the implementation workflow
and the user interface are described in detail.
This research aims to provide an implementation solution of combining BIM with smart contracts
for visualizing the real-time DAP process. Further implementation of the smart contract system should
still proceed. For example, the connection between the smart contract system with a CDE has not yet
been considered in the paper. In the future, a real use case will be applied to verify the designed smart
contracts. User feedback should be collected for feasibility and further improvement of the smart
contract system. In addition to the DAP processes, the visualization and automation of other
construction management processes such as supply chain process can be considered in the future.
The study was conducted as part of the BIMcontracts research project funded by the German Federal
Ministry for Economic Affairs and Energy (BMWi) within the "Smart Data Economy" technology
program (project number: 01MD19006B).
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