Table 6.

Differences between DDE and our CDE semantic relationships

CDE Semantic Type		Characteristic	Difference from a DDE
aCDE	Hybrid	Allowing the entry of multiple data types in a hybrid aCDE requires aCDEs that support different data types for the same data item	A DDE does not support the entry of multiple types of data
	Variable	Connecting to an outside dictionary database	No dictionary-associated constraint in a DDE
cCDE	General	Containing a set of aCDEs	Do not have output DE(s), but a DDE can be a cCDE
	Repeated	Allowing sequential data entry into a repeated cCDE	No repeated property in a DDE
	Dictionary	Bringing biomedical knowledge from an outside dictionary database to a dictionary cCDE containing a variable aCDE as a foreign key to the dictionary table with the repeated property	No dictionary connection allowed for a DDE
Constraint	Operated	Allowing mathematical/algebraic expressions between related aCDEs	A DDE has this constraint with the a CALCULATION type
	Required	Forcing aCDE to have a value other than null	No required constraint in a DDE
	Dependent	Dynamic enabling and disabling of an aCDE via a predicate	No dependent constraint in a DDE
	Ordered	Ordering a set of aCDEs	A DDE has this constraint by default

^a CALCULATION type in DDE only covers arithmetic operators (i.e., +, −, *, /) but, the operated constraints include not only arithmetic operators but also logical operators (i.e., <, >)