Ownership Labs, Open Marketplace for Decentralized Data. Almost everyday you open mobile applications like twitter and Amazon, for getting convenient services. However, you lose your data ownership in the era of data economy. You cannot control how your data is shared and sold, while service-matching platforms make huge profits from it and determine what you can see. So, our vision is to make the data flows more transparent and rebuild the service-matching schema in Web3. DataToken SDK implements a new decentralized data management and off-chain trusted computing middleware. It leverages the trusted features of blockchains to return data ownership to its owners while maintaining the computability and traceability of data. This is also a special use case of NFTs applied in data sharing and monetization. Data assets can be defined once but sold multiple times for private computation. This projects provide asset templates for data owners to define how data can be computed. So for data owners, instead of giving away data, they can maintain control of data, and have the choice to monetize it. DApps can create data unions to aggregate authorized datasets, e.g., a batch of user preferences or service features of NFTs. Data buyers can directly purchase aggregated data for computation, e.g., building NFT recommender systems. Specifically, DataToken is a new data service specification for traceable computation and hierarchical aggregation. Data owners can declare a permitted list of trusted operators and related constraints in the data service terms. Anyone who wants to use the source data must fulfill all service terms and get authorization for computation.