An analysis dataset that follows the ADaM Basic Data Structure (BDS), i.e., an analysis dataset of the BDS class, can contain multiple analysis parameters. In a BDS analysis dataset, the variable PARAM contains a unique description for every analysis parameter included in that dataset. The variable PARAMCD contains the short name of the analysis parameter in PARAM, with a one-to-one mapping between the two variables. Each value of PARAM identifies a set of one or more rows in the dataset.
The metadata for the columns (variables) in the dataset often depend on the values of PARAM/PARAMCD. This concept is analogous to that of value-level metadata for a single variable in SDTM, but in the BDS it is quite common that the metadata of several variables vary by PARAM/PARAMCD. To describe how variable metadata vary by PARAM/PARAMCD, the metadata element PARAMETER IDENTIFIER is required in variable-level metadata for a BDS analysis dataset. This PARAMETER IDENTIFIER metadata element identifies which variables have metadata that vary depending on PARAM/PARAMCD, and links the metadata for a variable to the appropriate value of PARAM/PARAMCD.
Controlled terminology reduces the need to enter the same metadata for a variable for multiple values of PARAM/PARAMCD:
- The use of “*ALL*” in the PARAMETER IDENTIFIER for a variable indicates that the metadata for that variable is the same for all values of PARAM/PARAMCD in the analysis dataset.
- The use of “*DEFAULT*” in the PARAMETER IDENTIFIER for a variable indicates that the specified metadata for that variable should be considered the metadata for all values of PARAM/PARAMCD in the analysis dataset unless otherwise specified.
- A particular value of PARAMCD in the PARAMETER IDENTIFIER for a variable indicates that the specified metadata for that variable should be considered the metadata applicable to the particular PARAMCD, overriding the specified *DEFAULT* metadata, if any.
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