Three instances, emp, skills, and dept, are defined over the Emp, Skills, and Dept relation schemas, respectively. The contents of these instances is described below.
There are two employees, identified by ED and DI in the following.
ED worked in the Toy department from 2/1/82 to 1/31/87, and in the Book department from 4/1/87 to the present. His name was Ed from 2/1/82 to 12/31/87, and Edward from 1/1/88 to the present. His salary was $20K from 2/1/82 to 5/31/82, then $30K from 6/1/82 to 1/31/85, then $40K from 2/1/85 to 1/31/87 and 4/1/87 to the present. ED is male and was born on 7/1/55. Several skills are recorded for ED. He has been qualified for typing since 4/1/82 and qualified for filing since 1/1/85. He was qualified for driving from 1/1/82 to 5/1/82 and from 6/1/84 to 5/31/88.
DI worked in and managed the Toy department from 1/1/82 to the present. Her name is Di throughout her employment. The budget of the Toy department was $150K from 1/1/82 to 7/31/84, $200K from 8/1/84 to 12/31/86, and $100K from 1/1/87 to the present. Her salary was $30K from 1/1/82 to 7/31/84, $40K from 8/1/84 to 8/31/86, then $50K from 9/1/86 to the present. DI is female and was born on 10/1/60. DI has been qualified for directing from 1/1/82 to the present.
The present time (i.e., the value of now) is 1/1/90.