DATA WAREHOUSE:
A data warehouse is a repository of integrated information, available for queries and analysis.

There are two  types of information systems
1. Operational systems.
2. Informational systems.

RULES:
1. Time dependent.
2. Non-volatile.
3. Subject Oriented.
4. Integrated.


Steps Involved in data Warehouse are as follows.

1.The data must be extracted from multiple, heterogeneous sources.

2.Data must be formatted for consistency within the warehouse.

3.The data must be cleaned to ensure validity.

4.The data must be fitted into the data model of the warehouse.

5.The data must be loaded in to the data warehouse.

ADVANTAGES:

Data warehouses are free from the restrictions of the transactional environment there is an increased efficiency in query processing.

Artificial intelligence techniques, which may include genetic algorithm and neural networks, are used for classification and are employed to discover knowledge from the data warehouse that may be unexpected or difficult to specify in queries.

APPLICATIONS:

1.MARKETING. 
2. FINANCE .
3. MANUFACTURING.
4.HEALTH CARE.