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Quiz 1
1. Define data warehouse as per father of data warehouse definition. (4 marks)
i)
Bill Inmon, the acknowledged father of the data warehouse, defines it as an
integrated, subject oriented, time-variant, non-volatile database that
provides support for decision making.
ii)
A data warehouse is a copy of transaction data specifically structured for
querying, analysis and reporting – Ralph Kimball
2. Explain 3 main components of data warehouse. (6 marks)
A data warehouse has three main components:
(Source : Data warehouse design, http://www.essentialstrategies.com/services/warehouse.htm)
- "central data warehouse" - is a database organized according to the
corporate data model.
- "data marts" — extracts from the central data warehouse that are organized
according to the particular retrieval requirements of individual users.
- "legacy systems" - where an enterprise's data are currently kept consist of
ODS of OLTP
3. Describe 2 differences between OLTP and data warehouse. (2 marks)
Online transaction processing – database system
Data warehouse – integrated database system from multiple sources
4. Explain the 4 main characteristics of data warehouse. (8 marks)
Subject Oriented:
Data that gives information about a particular subject instead of about a company's ongoing
operations.
Integrated:
Data that is gathered into the data warehouse from a variety of sources and merged into a
coherent whole.
Time-variant:
All data in the data warehouse is identified with a particular time period. All data in Data
Warehouse is accurate as of some moment in time, providing an historical perspective.
Non-volatile
Data is stable in a data warehouse. More data is added but data is never removed.
5. Define data mining. (4 marks)
6. Describe 3 differences between data warehouse and data mart. (6 marks)
7. Explain 4 components of metadata. (8 marks)
-
Business rules: includes definitions, derivations, related items, validation,
and hierarchy information (versions, dates, etc.).
-
Movement/transformation information: source/destination information,
as well as DDL (data types, names, etc.).
-
Operations
information:
data
load
job
schedules,
dependencies,
notification, and reliability information (such as host redirects and load
balancing).
-
Tool-specific information: graphic display information and special function
support.
-
Security rules: authentication and authorization.
8. Give 2 sins of data warehouse implementation by Kozar. (2 marks)
Kozar assembled a list of “seven deadly sins” of data warehouse implementation:


“If you build it, they will come” – the DW needs to be designed to meet people’s needs

Underestimating the importance of documenting assumptions – the assumptions and
potential conflicts must be included in the framework

Failure to use the right tool – a DW project needs different tools than those used to
develop an application

Life cycle abuse – in a DW, the life cycle really never ends
Omission of an architectural framework – you need to consider the number of users,
volume of data, update cycle, etc.

Ignorance about data conflicts – resolving these takes a lot more effort than most
people realize

Failure to learn from mistakes – since one DW project tends to be the cause of another,
learning from the early mistakes will yield higher quality later.
9. Draw a complete data warehouse. Include all the components that you have learnt in chapter 1 and
chapter 2 of the syllabus. (10 marks)