Enriching Smart Contracts with Temporal Aspects.

Blockchain technology provides a platform for the decentralized execution of smart contracts. A smart contract is an agreement that is automatically executed when certain conditions are met. Current smart contracts use business rules to express conditions in which transactions occur but lack the capability to reason over time. We present a model-driven approach for creating blockchain applications that can run temporal logic. We present the new concepts required at the model level and explain how these concepts can be translated to a blockchain solution applying Hyperledger Fabric, Hyperledger Composer, and PROTON complex event processing. We illustrate the approach using a pharma cold chain scenario. Cold chain scenarios are typical examples of blockchain cases in which temporal reasoning is required. Here, the blockchain provides transparency, a non-repudiation process, full traceability and trackability of the transactions (provenance), shorter lead times, and authentication and verification of the parties in the supply chain network at each asset transfer. The temporal reasoning is required since decisions about pharmaceutical quality is based on time windows in which the goods have been exposed to certain conditions. Our solution includes the model, the blockchain backend, and a mobile user interface that allows each certified and authorized party in the network to initiate actions, finish their transactions, and track progress. It also includes temperature monitoring to ensure compliance with the proper conditions for transportation and asset transfer.