The first syntactic extension, to indicate that an attribute is indeterminate, involves schema specification statements.
The second syntactic extension supports correlation credibility.
The third syntactic extension concerns ordering plausibility.
The final syntactic extension is to support indeterminate temporal literals.
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.
Since TSQL2 is an extension of SQL-92, we start with the syntactic extensions introduced in Section 4, specifically, indeterminate temporal attributes in the create table and alter table statements, correlation credibility in the from clause, and ordering plausibility in the where clause.