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Blockchain is one of the most popular distributed ledger technologies. It can solve the trust issue among enterprises. Hyperledger Fabric is a permissioned blockchain aiming at enterprise-grade business applications. However, compared to traditional distributed database solutions, one issue of blockchain based application development is the limited data access. For Fabric, the ledger data can only be retrieved by limited interfaces provided by Fabric SDKs or chaincode. In order to meet the requirements of data query and provide flexible query functions for real applications built on Fabric, this paper proposed a ledger data query platform called Ledgerdata Refiner. With ledger data analysis middleware, we provide sufficient interfaces for users to retrieve block or transaction efficiently. It is also able to track historical operations for any specific state. In addition, schemas of ledger state have been analyzed and clustered, which enable users to perform rich queries against ledger data. Finally, we validate the effectiveness of our query platform on a real application. Keywords-blockchain, Hyperledger Fabric, ledger data analysis, schema comparison, rich query, ledger analysis frameworkI.

Battery swapping is a solution of electric vehicle (EV) battery refueling. For EV owners, the battery information and transaction's correctness, openness, traceability and immutability is difficult to get guarantee in traditional centralized system. The trust lacking between EV owners and swapping station is caused, and becomes a big challenge to EV's rapid development. An objective mechanism based on decentralized blockchain system is proposed to manage battery swapping and solve the trust lacking issue. With this solution, both battery's life-cycle information and all operations histories are permanently saved in blockchain network. All key logics are driven by smart contracts, the battery price calculation and the digital currency exchange between EV owners and station are realized by smart contracts automatically and accurately. A primary prototype based on Ethereum is analyzed and implemented to illustrate the feasibility of managing battery swapping and refueling based on blockchain system to solve the trust lacking issue.