Supporting Long-term Transactions in Smart Contracts

Research on blockchains addresses multiple issues, with one being automating creation of smart contracts. One of the promising approaches, targeted for industry adoption, uses Business Process Model and Notation (BPMN) modeling to describe an application that is transformed into a smart contract. Although systems using this approach have been developed as a proof of concept, they do not address a major issue arising in the trade vertical that has applications involving collaboration of many actors over a long period of time. There are two difficulties: (i) BPMN's concept of a transaction is limited to actions of one actor, while trade transactions involve collaborations by many actors, and (ii) trade applications are long term and thus require support of transactional activities that span invocations of several methods of a smart contract. The difficulty is that a blockchain infrastructure supports the transactional properties only within the scope of one execution of one method of a smart contract. We extend the BPMN model by introducing the concept of a collaborative transaction to represent activities of many actors. In our previous research, we developed an approach, and a tool as a proof of concept, to transform a BPMN model into methods of a smart contract. In this paper we describe how collaborative transactions are supported by our approach even though the transaction activities span multiple calls to methods of a smart contract produced by transformation from a BPMN model to methods of a smart contract.