Data Mining: Practical Machine Learning Tools and Techniques, Second Edition

The real drawbacks of such techniques, however, are that they do not cope

well with noisy data, and they tend to be so slow as to be unusable on anything

but small artificial datasets. They are not covered in this book; see Bergadano

and Gunetti (1996) for a comprehensive treatment.

In summary, the input to a data mining scheme is generally expressed as a

table of independent instances of the concept to be learned. Because of this, it

has been suggested, disparagingly, that we should really talk offile miningrather

than database mining.Relational data is more complex than a flat file. A finite

set of finite relations can always be recast into a single table, although often at

enormous cost in space. Moreover, denormalization can generate spurious

regularities in the data, and it is essential to check the data for such artifacts

before applying a learning method. Finally, potentially infinite concepts can be

dealt with by learning rules that are recursive, although that is beyond the scope

of this book.

2.3 What’s in an attribute?

Each individual, independent instance that provides the input to machine

learning is characterized by its values on a fixed, predefined set of features or

attributes.The instances are the rows of the tables that we have shown for the

weather, contact lens, iris, and CPU performance problems, and the attributes

are the columns. (The labor negotiations data was an exception: we presented

this with instances in columns and attributes in rows for space reasons.)

The use of a fixed set of features imposes another restriction on the kinds of

problems generally considered in practical data mining. What if different

2.3 WHAT’S IN AN ATTRIBUTE? 49

Table 2.5 Another relation represented as a table.

First person Second person
Ancestor
Name Gender Parent1 Parent2 Name Gender Parent1 Parent2 of?

Peter male?? Steven male Peter Peggy yes
Peter male?? Pam female Peter Peggy yes
Peter male?? Anna female Pam Ian yes
Peter male?? Nikki female Pam Ian yes
Pam female Peter Peggy Nikki female Pam Ian yes
Grace female?? Ian male Grace Ray yes
Grace female?? Nikki female Pam Ian yes

other examples here yes

all the rest no