The third syntactic extension concerns ordering plausibility.
The final syntactic extension is to support indeterminate temporal literals.
The first syntactic extension, to indicate that an attribute is indeterminate, involves schema specification statements.
CREATE TABLE Received (Warehouse CHARACTER (30), Lot_Num INTEGER, Part CHARACTER (40), When INDETERMINATE DATE); CREATE TABLE In Production (Model CHARACTER (30), Serial_Num CHARACTER (10), During INDETERMINATE PERIOD (DATE)); ALTER TABLE Received ALTER COLUMN When TO NONSTANDARD DISTRIBUTION; The second syntactic extension supports correlation credibility.
First, we wanted the syntactic extensions to be minimal, yet highly expressive.
In this section, we summarize the syntactic extensions to SQL to support the storage and retrieval of valid-time indeterminate information from a database.
Four syntactic extensions to SQL are needed to support valid-time indeterminacy: (1) to indicate that a temporal attribute is indeterminate, (2) to specify the correlation credibility, (3) to specify the ordering plausibility, and (4) to indicate that a temporal literal is indeterminate.