AbstractAcknowledgements15.1. Introduction15.2. Data valuation: motivations and incentives15.3. Simple valuation methods15.4. Related work: conventional data valuation15.5. Extending to the federated setting: does it work?15.6. Vertical data valuation: feature valuation15.7. Horizontal data valuation: gradient valuation15.8. Learning-based valuation15.9. Conclusion and future workReferences