To harmonize data between studies participating in the consortium, study-specific datasets and Harmonized Datasets (i.e. variables targeted for harmonization) are used and made available to investigators. Variables collected by each study and those defined in the Harmonization Dataset are described using a standardized data dictionary which covers variable definitions and characteristics (e.g. type, unit, categories, and area of information covered). Once Collected Datasets and a Harmonized Dataset are defined and loaded in the system, variable-specific mapping algorithms are developed in order to derive the collected datasets into the common format defined in the Harmonization Dataset. In order to increase transparency of the harmonization process, these resources are made available to the research community.