Demand-Driven Open Data (DDOD) is an initiative by the U.S. Department of Health and Human Services aimed at improving access to data for various organizations to create economic and public health value. It offers a systematic, ongoing, and transparent mechanism for data users to communicate their needs and influence the data provided by HHS. Users can start by submitting their use cases through DDOD's GitHub page and actively participate in the process, which ensures better management and implementation of their data requests.