Developing blockchain interoperability solutions is costly and complex. Designers must ensure that their decisions comply with the required safety and liveness properties. A recent study proposed six blockchain interoperability design patterns to facilitate this development. However, they were informally described using natural language, which can lead to ambiguity and misinterpretation. The present study proposes to explore the use of Event-B to formalise the Temporal Transfer pattern, instantiated using a gateway-based approach, with the aim of solving these drawbacks. As a result, a formal specification was built that included eight safety properties. The specification was evaluated through formal verification and functional validation. The evaluation showed that the specification was correct by construction and all specified safety properties were verified. Furthermore, simulation enabled us to validate the functional behaviour of the specification. We consider the results of the present study promising and that they constitute a step forward in the formalisation of blockchain interoperability patterns.

Zero-knowledge proofs (zkp) have been used to address several blockchain limitations (e.g. privacy, scalability). Recent work has proposed its usage to improve blockchain interoperability solutions, aiming to help software architects and developers reduce barriers to blockchain adoption. However, more studies are needed to understand the full potential of zkp in this context. In this paper, we empirically analyse how zkp may improve a gateway-based solution for blockchain interoperability. The results showed that it was possible to improve the selected solution in terms of privacy and data confidentiality limitations, by incorporating anonymous cross-chain authentication and private data exchange. A prototype was developed and evaluated using three strategies: 1) its application in a use case scenario, 2) performance tests, and 3) cost analysis. The evaluation showed that the approach is technically feasible, but not suitable for every use case. Furthermore, the private data exchange approach confirmed the results of other studies: zkp is not mature enough for some scenarios, and more work is required in this area.

In recent years, multiple solutions have been proposed for blockchain interoperability. However, designing these solutions is complex, and design failures have caused great economic damage to their owners. Safety and liveness are essential properties for these solutions, and formalisation eases their verification. However, only a few efforts were performed to formalise interoperability solutions with known formal methods. TLA+ and PAT were previously used; however, the Event-B method has not been explored, although it might be a suitable approach. The purpose of this paper was to explore the formalisation of a gateway-based interoperability solution with Event-B. The results showed that the method was suitable and that a straightforward specification could be developed considering Ethereum and Hyperledger Fabric as the involved blockchains. The specification was assessed with three strategies that enabled its verification and validation. In particular, formal verification (e.g. safety properties), functional validation, and functional utility. These promising results constitute a step forward in the development of formal specifications for blockchain interoperability solutions.

Distributed ledger technologies (DLT) usage is currently limited to a single platform as they do not have design-based interoperability capabilities. In general, it's challenging for a DLT to communicate with another one. Although several DLT solutions have been proposed and applied in specific application areas, building a general-purpose interoperability solution for any DLT remains a challenge. In previous work, we proposed a tailor-made interoperability solution between Hyperledger Fabric and Corda. This paper extends that work to enable interoperability between Hyperledger Fabric and Ethereum. The main contribution of this paper is to provide a new approach to enable interoperability between these two DLT. The approach follows a new request-response interaction model and future payments to enable the payments of services. A prototype was developed and evaluated through a case scenario, performance tests and cost analysis. Performance tests showed bottlenecks under heavy load scenarios due to Ethereum's design. Costs analysis showed that the approach is suitable for purchasing high-priced services. These promising results constitute a step forward in developing a general-purpose solution for DLT interoperability.

During the last years, interoperability has become one of the main challenges within blockchain research as blockchains increasingly require integration between each other. Indeed, blockchains work by design in silos of information as interoperability is not a native feature. The main efforts in the field target permissionless blockchains, such as Bitcoin and Ethereum. However, interoperability in permissioned blockchains remains as an almost untouched area of work as they introduce additional requirements focusing on privacy and identity. Although there are some interoperability solutions for permissioned blockchains, they are either high-level design proposals not providing concrete implementations or focus on interoperability issues between business applications and blockchain platforms. In this paper we propose a gateway-based platform-to-platform interoperability solution for permissioned blockchains, which comprises a detailed solution design and a reference implementation. The proposal was assessed through the development of a social security case scenario, based on the reference implementation and using two blockchain platforms: Hyperledger Fabric and Corda.

Compliance management is gaining increasing interest in inter-organizational service-oriented systems, which are usually supported by integration platforms. Due to their mediation role and capabilities, these platforms constitute a convenient infrastructure for controlling compliance requirements affecting message exchanges between organizations. This paper proposes a formal model for a policy-based compliance control solution introduced in our previous work for such platforms. The model, which was developed using Event-B, provides unambiguous specifications and enables formal proofs as well as the verification of the solution operation.

The integration of software systems running in different healthcare organizations is increasingly required in order exchange data and carrying out healthcare processes in coordinated ways. This integration is usually supported by integration platforms which are based on advanced middleware technologies, like the Enterprise Service Bus (ESB). In addition, data quality in the healthcare area is critical to take timely and accurate decisions for the health and well-being of patients. This paper proposes a data quality aware ESB (DQ-ESB) for e-Health integration platforms which allows assessing and enforcing data quality within inter-organizational data exchanges. DQ-ESB handles an extensible data quality model which includes quality characteristics identified within the Uruguayan e-Health context. DQ-ESB provides data quality solutions based on native ESB mechanisms (e.g. data transformation) and it was implemented leveraging the Switchyard ESB product.

Organizations are progressively more required to collaborate with each other in order to achieve their business goals. This had led to the need of integrating the software systems of different, autonomous and geographically distributed organizations. Such integration is increasingly supported by integration platforms which are specialized middleware-based infrastructures that provide an intermediate processing layer, with integration capabilities, between organizations. This paper proposes a reference architecture for integration platforms supporting cross-organizational collaboration. The architecture is presented through four views where the main concepts, use cases and capabilities of these platforms are described.

Performing Bioinformatic's experiments involve an intensive access to distributed services and information resources through Internet. Existing tools facilitate the implementation of workflow-oriented applications, however they lack of capabilities to integrate services beyond low-scale applications, particularly integrating services with heterogeneous interaction patterns and in a larger scale. On the other hand, such integration mechanisms are provided by middleware products like Enterprise Service Buses (ESB). This paper proposes an integration platform, based on enterprise middleware, to integrate Bioinformatics services. It presents a multi-level reference architecture and focuses on ESB-based mechanisms to provide asynchronous communications, event-based interactions and data transformation capabilities.