assignment2

1.

Relation schema is the template for the datasets;

Relation is a dataframe;

An instance is an actual database.

Using the university database as an example:

Relation schema is that such university database should contain departments table, students table, employees table, and courses table, and these tables are connected with certain keys;

A relation in such schema is one of the said tables;

An istance is, for example, a UTD database with EPPS, JSOM and etc. department tables, UTD students tables, UTD employees table and UTD courses table connected with perdetermined sets of keys.

2.

3

Shown in the plot above.