CATERPILLAR: A Business Process Execution Engine on the Ethereum Blockchain

TL;DR

CATERPILLAR is a blockchain-based BPMN execution engine on Ethereum that maintains process state on-chain and uses smart contracts for workflow routing, enabling transparent and tamper-proof business process execution.

Contribution

It introduces a novel BPMN execution engine that integrates with Ethereum, supporting complex process constructs and on-chain process state management.

Findings

Supports a wide range of BPMN constructs.

Maintains process state directly on the blockchain.

Enables transparent and tamper-proof process execution.

Abstract

Blockchain platforms, such as Ethereum, allow a set of actors to maintain a ledger of transactions without relying on a central authority and to deploy scripts, called smart contracts, that are executed whenever certain transactions occur. These features can be used as basic building blocks for executing collaborative business processes between mutually untrusting parties. However, implementing business processes using the low-level primitives provided by blockchain platforms is cumbersome and error-prone. In contrast, established business process management systems, such as those based on the standard Business Process Model and Notation (BPMN), provide convenient abstractions for rapid development of process-oriented applications. This article demonstrates how to combine the advantages of a business process management system with those of a blockchain platform. The article introduces a blockchain-based BPMN execution engine, namely Caterpillar. Like any BPMN execution engine, Caterpillar supports the creation of instances of a process model and allows users to monitor the state of process instances and to execute tasks thereof. The specificity of Caterpillar is that the state of each process instance is maintained on the (Ethereum) blockchain and the workflow routing is performed by smart contracts generated by a BPMN-to-Solidity compiler. The Caterpillar compiler supports a large array of BPMN constructs, including subprocesses, multi-instances activities and event handlers. The paper describes the architecture of Caterpillar, and the interfaces it provides to support the monitoring of process instances, the allocation and execution of work items, and the execution of service tasks.