An associative database comprises two tables:
Items, each of which has a unique identifier,
a type and a name or a value.
Links, each of which has a unique identifier,
plus the identifiers of the source, association type ("verb")
and target of a fact that is recorded about the source.
Both the source and the target of a link may each
be an item or a link.
An item can represent an entity ("BA009"), a value
("10:25"), an entity type ("Airport") or a value
A link can represent an association ("BA009, departed
on, 10-Aug-2011") or an association type (Flight, departed
Both items and links also represent meta-types and instances, which
perform various functions in the database, such as recording schema