> For the complete documentation index, see [llms.txt](https://bdcatalyst.gitbook.io/biodata-catalyst-documentation/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://bdcatalyst.gitbook.io/biodata-catalyst-documentation/written-documentation/explore-available-data/understanding-data-harmonization-in-bdc.md). # Understanding Data Harmonization in BDC Data harmonization on NHLBI BioData Catalyst® (BDC) includes two primary approaches that researchers should understand when selecting datasets for analysis. Some datasets are harmonized directly by the original data generators or stewards, such as National Sleep Research Resource (NSRR), who apply domain-specific expertise and standardized protocols during data collection and curation. Other datasets are harmonized by secondary organizations or platforms, including members of the BDC consortium, which integrate and standardize data across studies to improve cross-study usability and interoperability. Because harmonization methods, variable definitions, and processing decisions may differ between these approaches, researchers should review the dataset summary information carefully before selecting data for analysis. Key details about harmonization processes, provenance, and any transformations applied should be clearly described within each dataset’s summary documentation to support transparent and informed use. --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://bdcatalyst.gitbook.io/biodata-catalyst-documentation/written-documentation/explore-available-data/understanding-data-harmonization-in-bdc.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.