In legal terms there is no ownership; there are contractual rights and limits. What is critical is that usage rights for raw data, processed data, and derivatives are allocated explicitly.
Two layers sit above the contract regardless of what it says. Any personal data in the set stays governed by KVKK/GDPR whoever “owns” the file, and in the EU a sui-generis database right can attach to the compiled data itself. So the allocation of usage rights should be read together with those overriding rights, not in isolation.
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