Hercule: Representing and Reasoning about Norms as a Foundation for Declarative Contracts over Blockchain

TL;DR

Hercule introduces a declarative approach to representing and reasoning about norms in blockchain contracts, enhancing flexibility and autonomy over traditional smart contracts by operationalizing norms over semistructured databases.

Contribution

It presents a novel method for specifying blockchain contracts through normative norms and computing their states using map-reduce on semistructured databases.

Findings

Processes thousands of events per second on Hyperledger Fabric

Operationalizes declarative contracts over semistructured databases

Enhances flexibility and autonomy in blockchain contracts

Abstract

Current blockchain approaches for business contracts are based on smart contracts, namely, software programs placed on a blockchain that are automatically executed to realize a contract. However, smart contracts lack flexibility and interfere with the autonomy of the parties concerned. We propose Hercule, an approach for declaratively specifying blockchain applications in a manner that reflects business contracts. Hercule represents a contract via regulatory norms that capture the involved parties' expectations of one another. It computes the states of norms (hence, of contracts) from events in the blockchain. Hercule's novelty and significance lie in that it operationalizes declarative contracts over semistructured databases, the underlying representation for practical blockchain such as Hyperledger Fabric and Ethereum. Specifically, it exploits the map-reduce capabilities of such stores to compute norm states. We demonstrate that our implementation over Hyperledger Fabric can process thousands of events per second, sufficient for many applications.