The valueType is a declared property of a variable that is required in
certain functions to determine handling of the variables. Specifically,
valueType refers to the
OBiBa data type of a variable.
The valueType is specified in a data dictionary in a column 'valueType' and
can be associated with variables as attributes. Acceptable valueTypes
include 'text', 'integer', 'decimal', 'boolean', datetime', 'date'. The full
list of OBiBa valueType possibilities and their correspondence with R data
types are available using valueType_list. The valueType can be used to
coerce the variable to the corresponding data type.