We describe a new paradigm for articulating need-to-protect and need-to-share policies that shows promise for enabling automated derivation of the downgrading rulesets needed to comply with these policies in systems that share data. This new paradigm is based on fine-grained semantic policy specifications in terms of context, content, Purpose, and Anti-purpose that are expressed in a machine-understandable language. Our approach is based on an existing reasoning capability that can handle simple downgrading cases. Extensions to handle more complex cases are discussed. Although not yet a complete, turnkey solution to the overall data sharing and privacy problem, we posit that our approach provides an auspicious research vector for future work towards achieving that goal.