DBMS-Stored Versus Derived Attributes
In some cases two (or more) attribute values are related—for example, the Age and BirthDate attributes of a person. For a particular person entity, the value of Age can be determined from the current (today’s) date and the value of that person’s BirthDate. The Age attribute is hence called a derived attribute and is said to be derivable from the BirthDate attribute, which is called a stored attribute. Some attribute values can be derived from related entities; for example, an attribute NumberOfEmployees of a department entity can be derived by counting the number of employees related to (working for) that department.
Calling Built-In Applications Using Intents Until this point, you have seen how to call activities within your own application. One of th...