Choreography Diagrams Research Articles

Blockchain-based Execution of BPMN Choreographies with Multiple Instances

The recent growth of blockchain has opened the use of technology for supporting the creation of new kinds of trustable systems. Model-driven engineering methodologies have been conceived to facilitate the automatic generation and deployment of software applications starting from the definition and refinement of abstract specification. BPMN choreography diagrams permit the representation of inter-organisational systems from a high-level perspective, just focusing on message exchange. However, the usage of such models in a blockchain-based setting has been limited to scenarios in which parties are involved in single interactions. This aspect becomes significantly relevant when considering complex applications, and in particular those in the realm of the Internet of Things. In these cases, the multiplicity of parties and their actions is crucial and requires novel solutions. In this work, we propose a novel approach for modelling, refining, deploying, and executing a Choreography on the blockchain, taking into account those scenarios in which the model includes multiple-instances. In particular, the considered models are translated into smart contracts able to correctly manage multiplicity. To demonstrate the approach’s feasibility, we designed and presented a Smart Thermostat application, that is executed on the Polygon blockchain.

A Flexible Approach to Multi-party Business Process Execution on Blockchain

In modern business scenarios, more and more organisations have to deal with the critical requirements of trustworthiness and flexibility, when collaborating in multi-party business processes. This calls for new kinds of systems able to manage collaborative processes in untrusted and dynamic environments. Concerning the collaborative perspective, the Business Process Management discipline has provided effective and standardised solutions for a long time, now. Regarding the trustworthiness perspective, blockchain is advocated as one of the most prominent technologies to guarantee trust in a multi-party setting. However, while the immutability of blockchain provides transparent and secure proof of past business interactions, it hinders the flexibility of the business process execution, as the business logic regulating the process execution is immutably stored in the blockchain. On the other hand, flexibility is a property that is becoming crucial in such a setting due to the high dynamism of the business scenarios. In fact, it permits to modify a process at run-time to deal with internal or external changes. In this paper, we face this issue by proposing an architecture for the flexible blockchain-based execution of multi-party business processes. In our approach, business processes are modelled by BPMN choreography diagrams translated into code, whose execution state is then stored in the blockchain. Flexibility is achieved by decoupling the business process’s logic from its execution state, thus allowing run-time changes to the process execution without losing the fundamental properties of trust provided by the blockchain. To show the effectiveness of our approach, we provide a prototypical implementation, called FlexChain, and we use it on a case study from the healthcare application domain. The results obtained by the analysis of cost for the reported case study show the feasibility of the approach. In particular, major costs to sustain relate to one-time operations, such as the deployment and the run-time update of the model, while the most frequent actions are quite efficient.

Engineering Trustable and Auditable Choreography-based Systems Using Blockchain

A key challenge in engineering distributed systems consists in the integration into their development of a decentralised infrastructure allowing the system participants to trust each other. In this article, we face such a challenge by proposing a model-driven methodology and a related framework to support the engineering of trustable and auditable systems. The approach is based on choreography diagrams specified in the Business Process Model and Notation standard, describing the interactions that should occur among the distributed components of systems. We support the whole lifecycle of choreographies, from their modelling to their distributed execution and auditing. The framework, based on blockchain technology, is named ChorChain. More specifically, ChorChain takes as input a BPMN choreography model and automatically translates it into a Solidity smart contract. The smart contract permits us to enforce the interactions among the cooperating components as prescribed by the choreography model. By leveraging on the auditability of blockchain, ChorChain also supports the activity of auditors continuously. In such a way, ChorChain enables auditors to get some degree of assurance on what happens simultaneously with, or shortly after, information disclosure. We assess the feasibility and effectiveness of the proposed methodology and framework through experiments conducted on the Rinkeby Ethereum Testnet.

Threat Representation Methods for Composite Service Process Models

The Business Process Modeling Notation (BPMN) has become a popular standard for expressing high level business processes as well as technical specifications for software systems. However, the specification does not contain native support to express security information, which should not be overlooked in today’s world where every organization is exposed to threats and has assets to protect. Although a substantial amount of work enhancing BPMN 1.x with security related information already exists, the opportunities provided by version 2.0 have not received much attention in the security community so far. This paper gives an overview of security in BPMN and investigates several possibilities of representing threats in BPMN 2.0, in particular for design-time specification and runtime execution of composite services with dynamic behavior. Enriching BPMN with threat information enables a process-centric threat modeling approach that complements risk assessment and attack scenarios. We have included examples showing the use of error events, escalation events and text annotations for process, collaboration, choreography and conversation diagrams.