USING dmFSQL FOR FINANCIAL CLUSTERING

Ramón Alberto Carrasco

Dpto. de Lenguajes y Sistemas Informáticos, Universidad de Granada, Granada, Spain

María Amparo Vila

Dpto. de Ciencias de la Computación e I.A., Universidad de Granada, Granada, Spain

José Galindo

Dpto. de Lenguajes y Ciencias de la Computación, Universidad de Málaga, Spain

Keywords: Clustering, Flexible Queries, Data Mining, Fuzzy SQL, Fuzzy Databases.

Abstract: At present, we have a dmFSQL server available for Oracle© Databases, programmed in PL/SQL. This

erver allows us to query a Fuzzy or Classical Database with the dmFSQL (data mining Fuzzy SQL)

language for any data type. The dmFSQL language is an extension of the SQL language, which permits us

to write flexible (or fuzzy) conditions in our queries to a fuzzy or traditional database. In this paper, we

propose the use of the dmFSQL language for fuzzy queries as one of the techniques of Data Mining, which

can be used to obtain the clustering results in real time. This enables us to evaluate the process of extraction

of information (Data Mining) at both a practical and a theoretical level. We present a new version of the

prototype, called DAPHNE, for clustering witch use dmFSQL. We consider that this model satisfies the

requirements of Data Mining systems (handling of different types of data, high-level language, efficiency,

certainty, interactivity, etc) and this new level of personal configuration makes the system very useful and

flexible.

1 INTRODUCTION

We can define Data Mining as the process of

extraction of interesting information from the data in

databases. According to (Frawley 1991) a

discovered knowledge (pattern) is interesting when

it is novel, potentially useful and non-trivial to

compute. A serie of new functionalities exist in Data

Mining, which reaffirms that it is an independent

area (Frawley 1991):

- High-Level Language. This representation is

esirable for discovered knowledge and for showing

the results of the user's requests for information (e.g.

queries).

- Certainty. The discovered knowledge should

accurately re

flect the content of the database. The

imperfectness (noise and exceptional data) should be

expressed with measures of certainty.

- Efficiency. The process of extraction of

nowledge should be efficient, i.e. the running time

should be predictable and acceptable when dealing

with very large amounts of data.

- Handling of Different Types of Data. There are

fferent kinds of data and databases used in diverse

applications (relational data, objects, hypertext, etc.)

so it would be desirable that a Data Mining system

would carry out its work in an effective way.

- Interactive Mining Knowledge at Multiple

straction Levels. The interactive discovery of

knowledge allows the user to refine a Data Mining

request on line, dynamically change data focusing,

progressively deepen a Data Mining process, and

flexibly view the data and Data Mining results at

multiple abstraction levels and from different angles.

- Mining Information from Different Sources of

Data. Cu

rrently the knowledge mining from

different sources of formatted or unformatted data

135

Alberto Carrasco R., Amparo Vila M. and Galindo J. (2005).

USING dmFSQL FOR FINANCIAL CLUSTERING.

In Proceedings of the Seventh International Conference on Enter prise Information Systems, pages 135-141

DOI: 10.5220/0002526801350141

 SciTePress

with diverse data semantic is perceived to be a

difficult challenge.

In this paper we discuss the implementation of

two prototypes for Data Mining purposes: we have

used a combination of DAPHNE which was initially

designed for clustering on numeric data types

(Carrasco, 1999) and dmFSQL which was designed

for fuzzy (or flexible) queries (Galindo 1998,

Galindo 1998b, Galindo 1999). At this point, we

would like to point out that Data Mining is an

autonomous and self-interesting field of research, in

which techniques from other fields could be applied.

Among these techniques are the use of dmFSQL

(data mining Fuzzy SQL), which is a database query

language which incorporates fuzzy logic. In

particular, we use dmFSQL to solve, in real time,

queries, which obtain objects (tuples) with similar

characteristics, i.e. objects of a specific group

through a process of clustering. Often, the clustering

is carried out on a set of examples from the database

and not on the entire database. We present some

experimental results with this alternative solution in

the context of a bank. This area needs a Data Mining

system tailored to its needs, because this area

manages very large databases and these data has a

very concrete meaning. Thus, data must be treated

according to this meaning. Finally, as conclusions

we consider that this model satisfies the

requirements of Data Mining systems [Chen 1996,

Frawley 2001) (handling of different types of data,

high-level language, efficiency, certainty,

interactivity, etc.) and this new level of personal

configuration makes the system very useful and

flexible.

2 dmFSQL A LANGUAGE FOR

FLEXIBLE QUERIES

The dmFSQL language (Galindo 1998, Galindo

1998b, Galindo 1999) extends the SQL language to

allow flexible queries. We have extended the

SELECT command to express flexible queries and,

due to its complex format, we only show an abstract

with the main extensions added to this command:

- Linguistic Labels: If an attribute is capable of

undergoing fuzzy treatment then linguistic

labels can be defined on it. These labels will be

preceded with the symbol $ to distinguish them

easily. They represent a concrete value of the

attribute. dmFSQL works with any kind of

attributes (see 2.1.1 section) therefore, by

example, a label can have associated: a

trapezoidal possibility (Figure 1), a scalar (if

there is a similarity relationship defined

between each two labels in the same domain), a

text, a XML document, etc.

Figure 1: Trapezoidal possibility distributions: A, B

- Fuzzy Comparators: In addition to common

comparators (=, >, etc.), dmFSQL includes

fuzzy comparators in Table 1. There are some

different kinds of fuzzy comparators. By

example a fuzzy comparator is used to compare

two trapezoidal possibility distributions A, B

with A=$[α

,β

,γ

,δ

] B=$[α

,β

,γ

,δ

] (see

Figure 1). In the same way as in SQL, fuzzy

comparators can compare one column with one

constant or two columns of the same type. More

information can be found in (Galindo 1998b,

Galindo 1999). These definitions can are based

in fuzzy set theory, classical distance functions

and other type of similarity functions.

Table 1: Fuzzy Comparators for dmFSQL

Fuzzy Comparator (fcomp)

for:

Possibility Necessity

Significance

FEQ NFEQ Fuzzy EQual

FGT

FGEQ

NFGT

NFGEQ

Fuzzy Greater Than

Fuzzy Greater or Equal

FLT

FLEQ

NFLT

NFLEQ

Fuzzy Less Than

Fuzzy Less or Equal

MGT

MLT

NMGT

NMLT

Much Greater Than

Much Less Than

- Fulfilment Thresholds γ: For each simple

condition a Fulfilment threshold may be

established with the format <condition>

THOLD

, indicating that the condition must be

satisfied with a minimum degree γ in [0,1]

fulfilled.

- CDEG(<attribute>) function: This function

shows a column with the Fulfilment degree of

the condition of the query for a specific

attribute, which is expressed in brackets as the

argument.

- Fuzzy Constants: We can use and store all of

the fuzzy constants (which appear in Table 2) in

ICEIS 2005 - ARTIFICIAL INTELLIGENCE AND DECISION SUPPORT SYSTEMS

136

dmFSQL.

Table 2: Fuzzy Constants of dmFSQL

F. Constant Significance

UNKOWN

UNDEFINED

NULL

Unknown value but the attribute is applicable

The attribute is not applicable or it is meaningless

Total ignorance: We know nothing about it

A=$[α

,β

, γ

,δ

]

$label

[n, m]

Fuzzy trapezoid (α

≤β

≤ γ

≤δ

): See Figure 1

Linguistic Label: It may be a trapezoid or a scalar

(defined in dmFMB)

Interval “Between n and m” (α

=β

=n and

=δ

=m)

Fuzzy value “Approximately n” (β

=γ

=n and n-

=δ

=margin)

2.1 Architecture of dmFSQL

In this section, we shall describe the first prototype

to be integrated in our approach. At present, we have

a dmFSQL Server available for Oracle© Databases,

mainly programmed in PL/SQL. The architecture of

the Fuzzy Relational Database with the dmFSQL

Server is made up by:

1. Data: Traditional Database and data mining

Fuzzy Meta-knowledge Base (dmFMB).

2. dmFSQL Server.

2.1.1 Data: Traditional Database and dmFMB

The data can be classified in two categories:

- Traditional Database: They are data from our

relations with a special format to store the fuzzy

attribute values. The fuzzy attributes are

classified by the system in 4 types:

- Fuzzy Attributes Type 1: These attributes

are totally crisp (traditional), but they have

some linguistic trapezoidal labels defined on

them, which allow us to make the query

conditions for these attributes more flexible.

Besides, we can use all constants in Table 2 in

the query conditions with these fuzzy

attributes.

- Fuzzy Attributes Type 2: These attributes

admit crisp data as well as possibility

distributions over an ordered underlying

domain. With these attributes, we can store and

use all the constants we see in Table 2.

- Fuzzy Attributes Type 3: These attributes

have not an ordered underlying domain. On

these attributes, some labels are defined and on

these labels, a similarity relation has yet to be

defined. With these attributes, we can only use

the fuzzy comparator FEQ, as they have no

relation of order. Obviously, we cannot store or

use the constants fuzzy trapezoid, interval and

approximate value of Table 2.

- Attributes Type 4: There are different kinds

of data in a database used in diverse

applications (relational data, objects, hypertext,

XML, etc.) therefore, it would be desirable that

a Data Mining system would carry out its work

in an effective way. In order to manage these

data we have defined these attributes. It is a

generic type (fuzzy or crisp), which admits

some fuzzy treatment. We permitted this

attribute is formed by more than a column of

the table (complex attributes). Therefore, with

attributes Type 4 is possible to redefine the

attributes Type 1, 2 and 3 using other

representations (by example, alternative

representation to the fuzzy trapezoid) or fuzzy

comparators. With these attributes, we can

store and use the constants linguistic label in

Table 2.

- data mining Fuzzy Meta-knowledge Base

(dmFMB): It stores information about the Fuzzy

Relational Database in a relational format. It

stores attributes which admit fuzzy treatment

and it will store different information for each

one of them, depending on their type:

- Fuzzy Attributes Type 1: In order to use

crisp attributes in flexible queries we will only

have to declare them as being a fuzzy attribute

Type

1 and store the following data in the dmFMB:

Trapezoidal linguistic labels: Name of the label

and α

, β

, γ

and δ

values (as in Figure 1).

Value for the margin of the approximate values

(see Table 1). Minimum distance in order to

consider two values very separated (used in

comparators MGT/NMGT and MLT/NMLT).

- Fuzzy Attributes Type 2: As well, as

declare them as being a fuzzy attribute Type 2,

these attributes have to store the same data in

the

dmFMB as the fuzzy attributes Type 1.

- Fuzzy Attributes Type 3: They store in the

dmFMB their linguistic labels, the similarity

degree amongst themselves and the

compatibility between attributes of this type,

i.e., the attributes that use the same labels and

that can be compared amongst them.

- Attributes Type 4: The dmFMB stores

information for the fuzzy treatment of the

attributes Type 4:

- Fuzzy Comparison Functions: The

user can define the functions of comparison

(Table 1) for the treatment of each attribute

of Type 4. The format is: CDEG (A fcomp

B) -> [0,1] with CDEG the compatibility

degrees, A, B two attributes or linguistic

USING dmFSQL FOR FINANCIAL CLUSTERING

137

labels Type 4 and fcomp any fuzzy

comparator in Table 1. The user can

associate each attribute functions already

defined in the dmFMB.

- Representation Functions: The user

can optionally define it to show the

attributes in a more comprehensible way.

Of course, the user can associate each

attribute functions already defined in the

dmFMB

- Linguistic labels: They represent a

concrete value of the attribute.

- Complex attributes: We permitted this

attribute is formed by more than a column

of the table. Therefore, the dmFMB stores

information on structure of the attributes

Type 4.

2.1.2 dmFSQL Server

It has been programmed mainly in PL/SQL and it

includes three kinds of functions for attributes Type

1, Type 2 and Type 3:

- Translation Function: It carries out a lexical,

syntactic and semantic analysis of the dmFSQL

query. If errors, of any kind whatsoever, are found, it

will generate a table with all the found errors. If

there are no errors, the dmFSQL query is translated

into a standard SQL sentence. The resulting SQL

sentence includes reference to the following kinds of

functions.

- Representation Functions: These functions are

used to show the fuzzy attributes in a

comprehensible way for the user and not in the

internally used format.

- Fuzzy Comparison Functions: They are utilized

to compare the fuzzy values and to calculate the

compatibility degrees (CDEG function).

As we have seen, Translation and Representation

Functions are included in the dmFMB for the

attributes Type 4.

3 USING dmFSQL TO

CLUSTERING PROCESS

In this section, we shall describe the integration of

dmFSQL Server to the clustering process. This is a

part of a project, which is currently under

investigation with some Spanish banks. It deals with

customer database segmentation, which allows

differentiated treatment of customers (Direct

Marketing).

Included in this project we have a prototype

called DAPHNE (Carrasco, 1999). It is a generic

tool for clustering focused on the financial

environment. The prototype uses techniques, which

come from diverse fields: hierarchical clustering,

unsupervised learning based on fuzzy-set tools,

statistical techniques, etc. In this paper, we show a

new version of DAPHNE witch incorporate the

dmFSQL Server to do effective clustering.

Following we explain the full process.

Operation of DAPHNE: In the first step, the

relevant features of the customers for the clustering

are chosen using the user's knowledge. For this

selection, the user can use a method that we have

developed for automatic selection of relevant

characteristics based on genetic algorithms (Martín-

Bautista 1998). Therefore, the user inserts a new

project for clustering in the meta-database of the

prototype specifying the table or view with the

source data (id_table_clustering) and the attributes,

which DAPHNE will use for the clustering

(col_clu

, col_clu

,…, col_clu

). Theses attributes

have to define in the dmFMB as Type 1, 2, 3 or 4

specifying their characteristics. The user does not

need to specify anything on the domains of the

previously used attributes. It is important to note that

they are not restriction: on the type of attributes to

use for the clustering process (text, scalar, binary,

numerical, etc) and the on possible uncertainty of the

value of this attributes (unknown, undefined, null

and certain degree of belong). Besides the user

specify the weight of each attributes in the clustering

process (w_clu

, w_clu

,…, w_clu

such that w_clu

∈ [0,1] with r=1..m and verifying )

∑

cluw

1 _

Subsequently the main processes of DAPHNE are

explained, as well as its underlying theoretical base:

1. Computing Ultrametric Distance Matrix (see

Figure 2): This process attempts to obtain the

population's ultrametric distance matrix. Since the

results by Dunn, Zadeh y Bezdek (Delgado 1996)

it has been well known that there is equivalence

between hierarchical clustering, max-min

transitive fuzzy relation, and ultrametric

distances. Therefore, in the ultrametric matrix all

the possible clustering that can be carried out on

the population specified. The “dendogram" or

“tree diagram" may be viewed as a diagrammatic

representation of the results of a hierarchical

clustering process which is carried out in terms of

the distance matrix. This process contains the

following treatments:

ICEIS 2005 - ARTIFICIAL INTELLIGENCE AND DECISION SUPPORT SYSTEMS

138

Benzécri

dmFS

⎟

⎠

⎞

⎜

⎝

⎛

1.0

5.7.0

2.15.6.0

6.5.2.5.0

7.6.7.6.7.0

⎟

⎠

⎞

⎜

⎝

⎛

1.0

5.5.0

15.15.5.0

5.5.2.5.0

.6.6.6.6.0

Figure 2: Computing a ultrametric distance

atrix (dendograme) for six elements

- Computing population's normalized (in [0,1])

distance matrix (by example, the matrix D in

Figure 2). For each pair of the population's

individuals (i, j) the distance that separates both

) is obtained using dmFSQL as following:

SELECT A1.ROW_ID AS i, A2.ROW_ID AS j,

1-(CDEG(A1.col_clu

)* wclu

+…+

CDEG(A1. col_clu

)* w_clu

) AS d

FROM id_table_clustering A1,

id_table_clustering A2

WHERE A1.ROW_ID < A2.ROW_ID

AND (A1.col_clu

fuzzy_ecomp

A2.col_clu

THOLD 0

| A1.col_clu

fuzzy_ecomp

A2.col_clu

THOLD 0

AND

A2.col_clu

fuzzy_ecomp

A1.col_clu

THOLD 0

| A1.col_clu

fuzzy_ecomp

A2.col_clu

THOLD 0

A2.col_clu

fuzzy_ecomp

A1.col_clu

THOLD 0)

AND … AND

(A1.col_clu

fuzzy_ecomp

A2.col_clu

THOLD 0

| A1.col_clu

fuzzy_ecomp

A2.col_clu

THOLD 0

AND

A2.col_clu

fuzzy_ecomp

A1.col_clu

THOLD 0

| A1.col_clu

fuzzy_ecomp

A2.col_clu

THOLD 0

A2.col_clu

fuzzy_ecomp

A1.col_clu

THOLD 0);

where fuzzy_ecomp

is the fuzzy equal

comparator (FEQ or NFEQ) chosen for the user

for the fuzzy attribute col_clu

. For each attribute

col_clu

the WHERE clausule has three optional

forms (specified by | symbol):

a) If fuzzy_ecomp

is symmetric:

A1.col_clu

fuzzy_ecomp

A2.col_clu

THOLD 0

b) Using a T-norm if fuzzy_ecomp

is not

symmetric:

A1.col_clum fuzzy_ecomp

A2.col_clu

THOLD 0

AND

A2.col_clum fuzzy_ecomp

A1.col_clu

THOLD 0

c) Using a T-conorm if fuzzy_ecomp

is not

symmetric:

A1.col_clum fuzzy_ecomp

A2.col_clu

THOLD 0

A2.col_clum fuzzy_ecomp

A1.col_clu

THOLD 0

- Computing population's ultrametric distance

matrix (by example, the matrix D’ in Figure 2). In

the distance matrix, each of the three elements

verifies the triangle inequality. The matrix is

transformed so that each of the three elements of

the ultrametric inequality is also verified. An

algorithm based on the method of Benzécri

(

Benzécri, 1976) is used. For this purpose, we use a

parallel algorithm using MPI (Quinn 2003).

2. Computing possible α -cuts: Since the ultrametric

matrix is finite, it contains only a finite set of

different values. Thus, for the hierarchical clustering

or ultrametric matrix we can always determine

unequivocally the set of all possible different α -

cuts, that is, the set of all different equivalence

relations associated with the matrix. In other words,

every α -cut implies a different partition or the

population's clustering. By example, in the Figure 2

the possible α -cuts are 0.1, 0.15, 0.2, 0.5 and 0.6.

3. Clustering: This process assigns each individual

in the population to a certain cluster. In order to do

so it is necessary to obtain a certain partition from

the ultrametric matrix. Therefore, the problem

consists of choosing an α -cut among the possible

α -cuts already obtained, according to the

hypothesis that no previous information about the

USING dmFSQL FOR FINANCIAL CLUSTERING

139

structure of the data is available. The partition can

be obtained in different ways according to the user's

choice:

- Absolute good partition. We obtain the partition

determined by the α -cut 0.5 (Vila 1979). By

example, in the Figure 2 the α -cut 0.5 determines

the classes {5, 6, 3} and {4, 2, 1}.

- A good partition. We use an unsupervised

learning procedure based on fuzzy-set tools. This

procedure determines a good partition as the

minimum value of a measure denned on the set of all

possible α -cuts (Delgado 1996).

- Partition that determines a certain number of

groups. By means of a binary search algorithm on all

possible α -cuts, we obtain the α -cut which

implies a number of groups which are closest to the

user's request.

4 EXPERIMENTAL RESULTS

This system has been applied to some problems of

the segmentation of bank customers in real life

situations. Here we show a particular case of

segmentation. The relevant attributes identified by

the banking expert have been:

- Payroll (payroll): is a binary attribute that

indicates if the client receives payroll through

the financial company (value 1) or not (value 0).

We decide define this attribute as Type 4

specifying a FEQ comparator in the dmFMB

based in the Sokal and Michener distance.

- Average account balance of the client in last 12

moths (balance): it is obtained through an

analytic study in the company data warehouse

system. This is a crisp attribute but we decide

define this as Type 1 in the dmFMB using the

uzzy constants value #n = 500 (approximately n,

see Table 2).

- Geographic area of clients (area): there are

three areas in the study: Madrid, Barcelona

(Spanish cities) and rest of World. Obviously,

this is a scalar attribute (Type 3), therefore we

define a similarity relationship for the FEQ

comparator in the dmFMB (see Table 3).

Table 3: Similarity relationship defined for area

area

Madrid Barcelona Rest of World

Madrid 1 0.6 0

Barcelona 1 0

Rest of World 1

Now we must specify the weight of each

attributes in the clustering process in order to better

focus the customers clustering according to the user

criteria. The weights chosen are 0.4 for area and

payroll and 0.2 for balance.

Finally, by means of a sample of a few tuples the

system here proposed has obtained six clusters as the

optimum number in the population (see Table 4).

Table 4: Results of clustering: six clusters

id_

client

area

pay

roll

balance

id_

cluster

93036 Rest of World 0 -959 1

60932 Rest of World 0 1 1

65940 Rest of World 0 35 1

07788 Madrid 0 10 4

87992 Madrid 0 241 4

67476 Madrid 1 1 2

44596 Madrid 1 16 2

14160 Madrid 1 141 2

11281 Madrid 1 353 2

65532 Madrid 1 631 2

74188 Madrid 1 965 2

18096 Barcelona 0 -36 5

45700 Barcelona 0 0 5

21184 Barcelona 0 5 5

10427 Barcelona 0 9 5

49867 Barcelona 1 0 6

01384 Barcelona 1 7 6

50392 Barcelona 1 1580 3

55689 Barcelona 1 1831 3

87752 Barcelona 1 1989 3

23952 Barcelona 1 2011 3

5 CONCLUSIONS

dmFSQL Server has been extended to handling of

different types of data (Carrasco 2002) and used as a

useful tool for certain Data Mining process

(Carrasco 1999, Carrasco 2001, Carrasco 2002) and

other applications (Galindo 1999). Now we have

applied dmFSQL for the clustering problem. Besides

the specific requirements of the clustering problem,

the prototype has been designed considering the

above-mentioned desirable functionalities of Data

Mining systems:

- Handling of Different Types of Data: The

possibility of combination any type of data for the

clustering process is considered novel in the

implementations of systems of this type.

- Mining Information from Different Sources of

Data: DAPHNE is very flexible when managing data

of different DBMS.

ICEIS 2005 - ARTIFICIAL INTELLIGENCE AND DECISION SUPPORT SYSTEMS

140

- Efficiency and Interactive Mining Knowledge:

The prototype has been designed to be interactive

with the user and to give the answer in real time in

order to obtain the wanted population's partition.

- Accuracy: The use of the classic method of

Benzécri to obtain the hierarchy of parts has

guaranteed the goodness of such a partition. In

addition, the procedure to obtain a good partition

based on fuzzy sets has given excellent results

during the tests.

- Friendly Interface: The interface of DAPHNE is

graphic and completely user guided. Like-wise, the

prototype includes a meta-database, in such a way

that the management of a clustering project can

become quick and easy for the user.

Regarding future works:

- we will show a theoretical study of the

properties of the new similarity functions

incorporated in this work (combining fuzzy set

theory, classical distance functions, etc.) and

how imply the clustering process;

- we will specify an extension of dmFSQL

language that includes clustering clausules;

- we will integrate DAPHNE functionalities into

dmFSQL Server.

REFERENCES

J.P. Benzécri et coll, 1976. L'analyse des données; Tomo

I: La Taxinomie; Tomo II: L'analyse des

correspondences. Paris, Dunod.

R.A. Carrasco, J. Galindo, M.A. Vila, J.M. Medina, 1999.

Clustering and Fuzzy Classification in a Financial

Data Mining Environment. 3rd International ICSC

Symposium on Soft Computing, SOCO'99, pp. 713-

720, Genova (Italy), June 1999.

R.A. Carrasco, J. Galindo, A. Vila, 2001. Using Artificial

Neural Network to Define Fuzzy Comparators in

FSQL with the Criterion of some Decision-Maker. In

Bio-inspired applications of connectionism.-2001, eds.

J. Mira and A. Prieto, Lecture Notes in Computer

Science (LNCS) 2085, pp. 587-594. Ed. Springer-

Verlag, 2001, ISBN: 3-540-42237-4.

R.A. Carrasco, M.A. Vila, J. Galindo, 2002. FSQL: a

Flexible Query Language for Data Mining. In

Enterprise Information Systems IV, eds. M. Piattini, J.

Filipe and J. Braz, pp. 68-74. Ed. Kluwer Academic

Publishers, 2002, ISBN: 1-4020-1086-9.

M. Chen, J. Han, P.S. Yu, 1996. Data Mining: An

overview from a Data Base Perspective. IEEE

Transac. On Knowledge and Data Engineering, Vol 8-

6 pp. 866-883.

M. Delgado, A.F. Gómez-Skarmeta, A. Vila, 1996. On the

Use of Hierarchical Clustering. In Fuzzy Modelling.

International Journal of Approximate Reasoning, 14,

pp. 237-257.

W.J. Frawley, G. Piatetsky-Shapiro, C.J. Matheus, 1991.

Knowledge Discovery in Databases: An Overview. In

G. Piatetsky-Shapiro, W.J. Frawley eds. Knowledge

Discovery in Databases pp. 1-31, The AAAI Press.

J. Galindo, J.M. Medina, O. Pons, J.C. Cubero, 1998. A

Server for Fuzzy SQL Queries. In Flexible Query

Answering Systems, eds. T. Andreasen, H.

Christiansen and H.L. Larsen, Lecture Notes in

Artificial Intelligence (LNAI) 1495, pp. 164-174. Ed.

Springer.

J. Galindo, J.M. Medina, A. Vila, O. Pons, 1998. Fuzzy

Comparators for Flexible Queries to Databases.

Iberoamerican Conference on Artificial Intelligence,

IBERAMIA'98, pp. 29-41, Lisbon (Portugal), October

1998.

J. Galindo, J.M. Medina, J.C. Cubero, O. Pons, 1999.

Management of an Estate Agency Allowing Fuzzy

Data and Flexible Queries. EUSFLAT-ESTYLF Joint

Conference, pp. 485-488, Palma de Mallorca (Spain),

September 1999.

M.J. Martín-Bautista, M.A. Vila, 1998. Applying Genetic

Algorithms to the Feature Selection Problem in

Information Retrieval. In Flexible Query Answering

Systems, eds. T. Andreasen, H. Christiansen and H.L.

Larsen, Lecture Notes in Artificial Intelligence

(LNAI) 1495, pp. 272-281. Ed. Springer.

M.J. Quinn, 2003. Parallel Programming in C with MPI

and OpenMP. McGraw-Hill.

F.E. Petry, 1996. Fuzzy Databases: Principles and

Application (with chapter contribution by Patrick

Bosc). International Series in Intelligent Technologies.

Ed. H.-J. Zimmermann. Kluwer Academic Publishers

(KAP).

M.A. Vila, 1979. Nota sobre el cálculo de particiones

óptimas obtenidas a partir de una clasificación con

jerárquica. Actas de la XI Reunión Nacional de I.O.,

Sevilla, España.

USING dmFSQL FOR FINANCIAL CLUSTERING

141