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Chapter 1 Introduction
Knowledge
Figure 1.3
Data mining—searching for knowledge (interesting patterns) in data.
appropriately named “knowledge mining from data,” which is unfortunately somewhat
long. However, the shorter term, knowledge mining may not reflect the emphasis on
mining from large amounts of data. Nevertheless, mining is a vivid term characterizing
the process that finds a small set of precious nuggets from a great deal of raw material
(Figure 1.3). Thus, such a misnomer carrying both “data” and “mining” became a pop-
ular choice. In addition, many other terms have a similar meaning to data mining—for
example, knowledge mining from data, knowledge extraction, data/pattern analysis, data
archaeology, and data dredging.
Many people treat data mining as a synonym for another popularly used term,
knowledge discovery from data, or
KDD, while others view data mining as merely an
essential step in the process of knowledge discovery. The knowledge discovery process is
shown in Figure 1.4 as an iterative sequence of the following steps:
1.
Data cleaning (to remove noise and inconsistent data)
2.
Data integration (where multiple data sources may be combined)
3
3
A popular trend in the information industry is to perform data cleaning and data integration as a
preprocessing step, where the resulting data are stored in a data warehouse.
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1.2 What Is Data Mining?
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Flat files
Databases
Data
Warehouse
Patterns
Knowledge
Cleaning and
integration
Selection and
transformation
Data
mining
Evaluation and
presentation
Figure 1.4
Data mining as a step in the process of knowledge discovery.
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Chapter 1 Introduction
3.
Data selection (where data relevant to the analysis task are retrieved from the
database)
4.
Data transformation (where data are transformed and consolidated into forms
appropriate for mining by performing summary or aggregation operations)
4
5.
Data mining (an essential process where intelligent methods are applied to extract
data patterns)
6.
Pattern evaluation (to identify the truly interesting patterns representing knowledge
based on interestingness measures—see Section 1.4.6)
7.
Knowledge presentation (where visualization and knowledge representation tech-
niques are used to present mined knowledge to users)
Steps 1 through 4 are different forms of data preprocessing, where data are prepared
for mining. The data mining step may interact with the user or a knowledge base. The
interesting patterns are presented to the user and may be stored as new knowledge in the
knowledge base.
The preceding view shows data mining as one step in the knowledge discovery pro-
cess, albeit an essential one because it uncovers hidden patterns for evaluation. However,
in industry, in media, and in the research milieu, the term data mining is often used to
refer to the entire knowledge discovery process (perhaps because the term is shorter
than knowledge discovery from data). Therefore, we adopt a broad view of data min-
ing functionality: Data mining is the process of discovering interesting patterns and
knowledge from large amounts of data. The data sources can include databases, data
warehouses, the Web, other information repositories, or data that are streamed into the
system dynamically.
1.3
What Kinds of Data Can Be Mined?
As a general technology, data mining can be applied to any kind of data as long as the
data are meaningful for a target application. The most basic forms of data for mining
applications are database data (Section 1.3.1), data warehouse data (Section 1.3.2),
and transactional data (Section 1.3.3). The concepts and techniques presented in this
book focus on such data. Data mining can also be applied to other forms of data (e.g.,
data streams, ordered/sequence data, graph or networked data, spatial data, text data,
multimedia data, and the WWW). We present an overview of such data in Section 1.3.4.
Techniques for mining of these kinds of data are briefly introduced in Chapter 13. In-
depth treatment is considered an advanced topic. Data mining will certainly continue
to embrace new data types as they emerge.
4
Sometimes data transformation and consolidation are performed before the data selection process,
particularly in the case of data warehousing.
Data reduction may also be performed to obtain a smaller
representation of the original data without sacrificing its integrity.