 The Data Dictionary is a compilation of all the data structures currently defined in NDA. Each structure represents a standardized definition of a measure or instrument used by researchers to collect and submit data. To view the detailed definition of an individual structure, click on the structure's title. Select one or more structures on this page and add them to the Filter Cart as one filter. Like in all NDA query tools, the contents of one filter are queried on an ‘OR' basis. Multiple filters return filtered results on an ‘AND' basis. 