Legend.

PK - primary key
FK - foreign key
AK - alternate key

Description of Relationships.

1. The "employs" relationship between Department and Employee shows that each department can have several employees, and each employee can be employed by one department. The table representing Department entity is a look-up table that has the list of departments. The table representing Employee entity has all the pertinent information about each employee that is or has been employed by the company.

2. The "submits" relationship between Employee and Expense shows that each employee can submit several expense reports and each expense report can be submitted by only one empoyee. The table representing Expense entity stores information pertaining to the whole report, not on a detailed level. For detailed information refer to #3.

3. The "consists of" relationship between Expense and Expense detail entities shows that each expense report may have several detail items and each detail item belongs only to one expense report. The table representing Expense Detail entity stores information about each expense detail item for each given expense report.

4. The "is described by" relationship between Expense Detail and Entertainment Details shows that each expense detail item may have several several names of persons that were entertained. The table representing Entertainment Details stores all the important information regarding the people entertained.

5. The "is classified by" relationship between Entertainment Detail and Expense Type serves as a look-up table for the expense type IDs in Expense Detail Entity.