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

much practical use in real-life problems because they rarely involve “closed”

worlds in which you can be certain that all cases are covered.

Neither table in Figure 2.1 is of any use without the family tree itself. This

tree can also be expressed in the form of a table, part of which is shown in Table

2.3. Now the problem is expressed in terms of two relationships. But these tables

do not contain independent sets of instances because values in the Name,

Parent1, and Parent2 columns of the sister-ofrelation refer to rows of the family

tree relation. We can make them into a single set of instances by collapsing the

two tables into the single one of Table 2.4.

We have at last succeeded in transforming the original relational problem

into the form of instances, each of which is an individual, independent example

46 CHAPTER 2| INPUT: CONCEPTS, INSTANCES, AND ATTRIBUTES

first

person

second

person

Peter

M

Peggy

F

= Grace

F

Ray

M

=

Pam

F

Ian

M

Steven =

M

Graham

M

Pippa

F

Brian

M

Anna

F

Nikki

F

Peter

Peter

...

Steven

Steven

Steven

Steven

...

lan

...

Anna

...

Nikki

Peggy

Steven

......

Peter

Graham

Pam

Grace

......

Pippa

......

Nikki

.....

Anna

sister

of?

no

no

no

no

yes

no

yes

yes

yes

first

person

second

person

Steven

Graham

lan

Brian

Anna

Nikki

Pam

Pam

Pippa

Pippa

Nikki

Anna

sister

of?

yes

yes

yes

yes

yes

yes

All the rest no

Figure 2.1A family tree and two ways of expressing the sister-of relation.