Information systems automate parts of business processes and support involved stakeholders. Recently, blockchains and other distributed ledgers are considered to extend the possibilities for automating inter-organizational processes: these technologies o er a new paradigm for such processes as they may automatically enforce contractual agreements without a trusted third party. Although existing research shows that inter-organizational processes can be enacted based on blockchains, fundamental question, such as What is the impact of blockchain on the process?, remain open. This work focuses on analyzing the duration of blockchain-based inter-organizational processes using simulation techniques.
With business process management (BPM), enterprises can structure, document,
and enact their processes [
Process engines use various technologies: databases store process relevant
data, mobile devices enable ubiquitous access, IoT technologies establish
cyberphysical connections, and more. Recently, the BPM community researches the
application of blockchain, especially in inter-organizational processes [
However, for some inter-organizational business processes, blockchain-based
solutions are ine cient and not viable. Some methods employ model-driven
development to speed up the development cycle, but expertise and manual e ort
is required for blockchain-speci c con gurations. For enterprises it is di cult to
decide whether a blockchain is applicable and whether it is e cient enough to
be viable. Additionally, most of the current solutions are tailored to one speci c
blockchain implementation (e.g., Ethereum [
In this paper, we sketch an approach for analyzing the duration of blockchainbased business processes using simulation. The analysis is based on a con gurable model of the blockchain's behavior, which can be integrated in process models to simulate the blockchain's impact on the process execution. Combined with general information (e.g., the technology's security guarantees), the results help businesses to make an informed decision about whether to apply blockchain.
The remainder of this paper starts with an example and an overview of works on blockchain-based BPM (Section 2). In Section 3, we present our approach of estimating the duration of blockchain-based processes. Finally, we discuss our approach and list directions for future work (Section 4). 2
In BPM, blockchains are mostly applied to inter-organizational (collaborative)
business processes [
The so called 2nd generation of blockchains supports smart contracts: programs that are executed by the nodes of the blockchain network. Just as the blockchain-stored ledger, smart contracts are tamper-proofed, transparent, and permanent. These properties guarantee that the program is executed when it is called (stopping the execution requires manipulating the ledger); thus, smart contracts can enforce contractual agreements. Since inter-organizational process models describe an agreement on responsibilities (by whom and in which order are actions performed?), smart contracts can enforce them. 2.1
The BPM community focuses mostly on the blockchains with smart contract
capabilities. The degree of blockchain integration can vary from simple
monitoring tools to blockchain-based process engines: Weber et al. demonstrated
blockchain-based monitoring and execution of inter-organizational business
processes [
Generating smart contracts from process models reduces the development
time. However, blockchain-based process execution may have non-functional
requirements, i.e., temporal constraints. The mentioned works help to estimate
aspects such as the duration; however, this still involves manual con guration
and a blockchain setup. The same holds for the work by Yasaweerasinghelage et
al.: their approach uses process simulation to send transaction to a blockchain
in order to estimate its latency [
Buyer Transfer Money to Escrow
Bank 15-20 min
Bank Transfer Money
Buyer 3 d* 3 d* 0 min
Bank Inform about
Escrow Auctioneers 1 min
Expert Cancel Escrow
Bank 15-30 min
Bank Transfer Money
Auctioneers
3 d*
10 min*
sent and being detected by the initiator of the next task (annotated on edges) [
A blockchain is a decentralized system for reaching consensus in a peer-to-peer network. Due to its nature, blockchains introduce additional latency: transactions are submitted, shared, veri ed and processed, and eventually incorporated in the consensus. Afterwards, participants are accountable for their transactions.
Inter-organizational business processes can employ blockchain in various ways. For the art-dealing example, we consider blockchain-based process execution: The bank is replaced by a smart contract and all interactions are logged by a smart contract, which enforces the right ordering of the actions. The triggering participant sends a transaction at the end of each interaction, i.e., the auctioneers send the transaction for the shipment after handing over the artwork.
The transactions trigger the progression of the on-chain process instance. The network managing the ledger processes a transaction in steps: a local transaction is shared with the network but remains pending, a pending transaction is mined (included in a block that extends the ledger), and the mined block with all its transactions is con rmed (succeeded by a certain number of blocks). The duration of each step depends mostly on the blockchain and the underlying network: in Bitcoin, a transaction needs a couple of seconds to spread, and a new block is appended approximately every 10 minutes; for Ethereum, transactions di use the network similarly fast; however, a block is added every 15 seconds. We assume that a transaction is included in the rst block that is mined after the transaction became available to the network (the reality may be more complex and in uenced by transaction fees, network load, and throughput).
In most cases, a participant waits for all preceding transactions to be conrmed. However, if the same participant triggers two subsequent interactions, the participant does not need con rmation of his or her own action. Additionally, if an interaction is physically, such as shipping the artwork, the transaction must be con rmed and the interaction must be completed.
Figure 2 partially shows a timed Petri net representation of the inter-organizational process. Each interaction task of the choreography model is translated into corresponding transitions: the ring of such a transition indicates the completion of the respective interaction. It progresses the state by producing an unnamed token for the control ow. Further, each interaction puts a token identifying the interaction on the Transaction Local place. The net includes the blockchainbased transaction processing: a transaction is sent, di uses the network, is included in a block, and eventually the block is con rmed. The transition Mine Block consumes all tokens on Transaction Pending and produces respective tokens on Transaction Included. Each interaction depends on the previous one; thus, the respective transition can only re if the previous transaction is ....
Artwok Deliverd
Transaction
Local <0.5– 1.5d> Request Assessment txRA
...
ArtworkAssessed
ArtworkisFake txRA <diffusion-time>
Diffuse Network
* TransactionPending <1.5– 2.5d> Return Artwork txRA2 <interblock-time>
Mine
Block TimeofLastBlock
ArtworkReturned
txRA2 ... in the place Transaction Confirmed. This requirement is represented by the labels on the respective arcs. In the example, the expert is performing two actions in a row, and does not need con rmation of the rst transaction. The transitions with label Cancel Escrow represent the di erent options: the escrow can be canceled immediately after Return Artwork; thus, there is a transition for Cancel Escrow for each possible state of the Return Artwork transaction (local, pending, included and con rmed).
Each transition is annotated with ranges for the duration of the respective
choreography task/blockchain action [
The Petri net semantics equipped with temporal information of the choreography and a blockchain con guration allow a simulation of the blockchain-based 1 Bitcoin di usion-time: http://bitcoinstats.com/network/propagation/ (02/06/2019) 2 Ethereum inter-blocktime : https://etherscan.io/chart/blocktime (02/06/2019) inter-organizational process. We use CPNTools3 to model4 all aspects of the Petri net and simulate the process quantitatively and manually step-through simulation techniques. Running 100 instances, we derived an average duration of about 8 days for the version not using blockchain and about 3 days for a blockchain-based version (0 min di usion-time, 10 min inter-blocktime, 6 blocks con rmation-count; duration ranges where simulated via a binomial distribution). While the blockchain causes delays, it enables process changes that reduce the overall duration: in the example, the replacement of the bank improved the process performance. By simply adjusting the blockchain con guration, it is possible to estimate other blockchain implementations. 4
In some cases, blockchain technologies may remove the need for trusted intermediaries in inter-organizational business processes. However, such solutions have drawbacks: the distributed nature limits the throughput and causes latency. We sketched a method to analyze the duration of blockchain-based processes.
The analysis relies on formal semantics, domain speci c information, and a con guration for a certain blockchain implementation. The con guration comprises three parameters; thus, adapting to di erent blockchains is simple. Through simulation, the analysis estimates the duration of blockchain-based processes with little e ort compared to prototypical and model-driven implementations. However, the impact of blockchain-based implementations on processes is not always signi cant: especially processes that are executed frequently and that are highly automated might be slowed down by blockchains. Processes that contain various manual and physical tasks may be delayed insigni cantly by blockchains or even speed up as manual tasks are automated or third parties are replaced by smart contracts.
The presented work is in an early state. In future work, we will support
BPMN choreography models by integrating our approach into a business process
simulator, which takes a blockchain con guration as well as an enriched BPMN
choreography model as an input. Additionally, di erent ways of blockchain-based
process support exist: we want to investigate existing solutions (such as
Caterpillar) to estimate di erent implementations and paradigms. Furthermore, the
blockchain behavior can be modeled and con gured on di erent granularity
levels: currently we do not consider that blocks are limited in size, the processing
of transactions might be prioritized based on transaction fees, and that block
propagation depends on various factors [
Additionally, execution time of processes is only one aspect a ected by the underlying technology. Public blockchains include a cryptocurrency: a transaction has costs depending on its priority and payload. This may or may not have a signi cant impact on the overall costs of a process. Related to both costs and 3 CPNTools homepage: https://cpntools.org (1/7/2019) 4 Models and results: https://owncloud.hpi.de/index.php/s/iGVqu7WkgMYXIpW duration is the throughput of blockchains: when a blockchain is used for multiple purposes or by many participants, transactions may remain pending longer.
Analyzing various aspect of blockchain-based processes requires a detailed
understanding of the technologies as well as the con guration points. In future
work, we will explore such behavioral properties and derive a formal model of
blockchains that can be con gured towards speci c implementations. Detailed
models can provide insights in blockchain's behavior as well as its impact on
business processes beyond latencies. Such models equipped with empirical data
[