2.2.4.3 Identifiers
Attributes that name, or identify entity instances. For
example Employee instances could be identified by Social Security Number,
Employee Number.
2.2.4.4 Relationships
Relationships are the glue that holds together the various
components of an E-R model. Intuitively, a relationship is an association among
the instances of one or more entity types that is of interest to the
organization.
2.2.4.5 Entity-Relationship Diagram
It is a pictorial representation of the entities and the
relationships between them. It allows the participants in the meeting to easily
see the information structure of the application.
2.2.4.6 Normalization
Normalization is the process of organizing data to minimize
redundancy. Normalization usually involves dividing a database into two or more
tables and defining relationships between the tables. The objective is to
isolate data so that additions, deletions, and modifications of a field can be
made in just one table and then propagated through the rest of the database via
the defined relationships.
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2.2.6 Data warehouse 2.2.6.1 Definition
A subject-oriented, integrated, time-variant, no updatable
collection of data used in support of management decision making processes and
business intelligence.
Formal systems definition of a data warehouse is a computer
database and its supporting components that is:
Subject oriented, meaning that the data in the database is
organized so that all the data elements relating to the same real-world event
or object are linked together;
Integrated, meaning that the database contains data from most
or all of an organization's operational applications, and that this data is
made consistent.
Time variant, meaning that the changes to the data in the
database are tracked and recorded so that reports can be produced showing
changes over time;
No updatable, meaning that data in the database is never
over-written or deleted, but retained for future reporting and users access the
data warehouse by means of variety of query languages and analytical tools.
Results may be fed back to data warehouse and operational databases.
A data warehouse is a store of enterprise data that is
designed to facilitate management decision making. A data warehouse includes
not only data but also tools, procedures training personnel, and other
resources that make access to the data easier and more relevant to decision
makers. The goal of the data warehouse is to increase the value of
organization's data asset.
The following is the figure explaining the role of data
warehouse which is to store extracts from operational data and make those
extracts available to users in a useful format.
Images
Other data
Files
DB
DB
DB
Data
warehouse
Departmental server
Departmental
User computer
User computer
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Figure 1: Role of data warehouse
Source: DAVID M.KROENKE, processing
fundamental design and Implementation, Sixth edition, p.382.
The data can be extracts from databases and files, but it can
also be document images, recordings, photos, and other no scalar data. The
source data could also purchased from other organizations. The data warehouse
stores the extracted data and also combines it, aggregates it, transforms it,
and makes it available to users via tools that are designed for analysis and
decision making
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