<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Archiving and Interchange DTD v1.0 20120330//EN" "JATS-archivearticle1.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>A Constrained Method of Constructing the Logic Classification Trees on the Basis of Elementary Attribute Selection</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Igor Povkh</string-name>
          <email>Igor.povkhan@uzhnu.edu.ua</email>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Uzhgorod National University</institution>
          ,
          <addr-line>89 B, Zankovetska str., Uzhgorod, 88000</addr-line>
          ,
          <country country="UA">Ukraine</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>A problem of constructing the logic classification tree model on the basis of a constrained elementary attribute selection method for the geologic data array has been considered. The method of the real data array approximation by a set of elementary attributes with a fixed criterion of the branching procedure stopping at the stage of constructing the classification tree has been suggested. This method allows the desired model accuracy to be provided, its structural complexity to be reduced and the necessary efficiency indices to be achieved. Based on the suggested elementary attribute selection method modification, the software has been developed enabling a set of different-type applied problems to be used.</p>
      </abstract>
      <kwd-group>
        <kwd>logic classification tree</kwd>
        <kwd>image recognition</kwd>
        <kwd>classification</kwd>
        <kwd>attribute</kwd>
        <kwd>branching criterion</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>The classification tree methods, the regressive trees used actively both for the
artificial intellect theory problems, being the means of decision adoption support and big
data array analysis, and for the related practical field of economy, management etc
[1] still remain an important segment of the decision tree concept application. The
principal available methods of training selection processing at the recognition
function constructing do not allow the required accuracy level of the recognition system to
be achieved and their complexity in the data system construction process to be
regulated [2, 3]. This shortcoming is not peculiar for the recognition system construction
methods based on the logic classification tree methods.</p>
      <p>Classification trees are one of the basic methods of automatic data analysis. The
first comprehensive studies and concepts of the idea of using the decision/
classification trees date back to the works of S. Hawland and E. Hunt [4]. Note that the logic
classification tree (LCT) flexibility, i.e. the ability to take into account and investigate
sequentially the effect of the influence of certain variables and structure attributes, is
their important specific feature. Respectively, there are a series of reasons providing
the LCT structures with higher flexibility as compared to the traditional data analysis
methods and tools. For instance, the ability to perform one-dimensional branching to
analyze the influence (importance, quality) of certain variables allows one to work
with different-type variables in a form of predicates [5].</p>
      <p>The problem of selecting the branching stopping rule (the LCT construction
stopping criterion) is a basic issue in the classification tree construction. Analyzing the
available logic tree construction methods and algorithms, one may distinguish two
basic approaches in this direction, i.e. the use of the statistical methods of estimation
of the necessity of further manifold partitioning/branching (the so called early
stopping or pre-pruning) and application of the logic tree depth (number of layers)
limitation scheme.</p>
      <p>Thus, let us note that the LCT construction method scheme described, e.g., in [6, 7],
has one principal disadvantage related to the fact that the number of elementary
attributes in the tree increases considerably with the number of vertices in the logic tree
structure (the LCT layer increase). Certainly, such complication of the resulting LCT
affects negatively the apparatus possibilities of the recognition system (i.e. memory,
processor time). The LCT method modification (the constrained method) on the basis
of a stage-by-stage selection of elementary attributes shall be suggested to overcome
the above negative issues.</p>
      <p>In practice, the LCT construction algorithms and methods quite often provide at
the output the structurally complicated logic trees (in the meaning of the number of
vertices, number of branches, belonging to the class of non-regular trees) that are not
uniformly filled with the data and have different number of branches. Such
complicated tree-like structures are quite difficult to be used in the external analysis due to a
large number of nodes (vertices) and step-by step partitions of the initial training
selection (TS) that contain minimal number of objects (in the worst case, possibly, even
single objects). Obviously, it is better to have a certain LCT with a minimal number
of vertices (nodes) that correspond to the absolute majority of the initial TS objects.
Just at this stage a principal problem of the LCT theory appears, i.e. the problem of
possible construction of all the logic tree variants that correspond to the initial TS and
the minimal by depth (number of layers) logic tree selection [8–12].</p>
      <p>2</p>
    </sec>
    <sec id="sec-2">
      <title>Formal problem statement</title>
      <p>
        Let the TS be defined in the following form:
( x1, f R ( x1 )),..., ( xm , f R ( xm )) .
(
        <xref ref-type="bibr" rid="ref1">1</xref>
        )
      </p>
      <p>Note that here xi  G, f R ( xi ) {0,1,..., k 1} , (i  1,2,..., m) , m is a number
of objects with TS; f R ( xi ) is a certain finitely significant function that defines the
partition R of the manifold G into the classes (images) H 0 , H1,..., H k 1 . Relation
f R ( xi )  l , (l  0,1, ,..., k 1) means that xi  H l , where xi  {xi1 , xi2 ,..., xin } ,
xi1 are the values of the j  th attribute for the object xi , ( j  1,2,..., n) , and n is a
number of attributes in the TS.</p>
      <p>
        Thus, the TS is the array (more strictly, the sequence) of certain sets, and each set
is the array of values of certain attributes and functions of the above set. One may say
that the array of the attribute values is a certain pattern, whereas the value of the
function relates the above pattern to the relevant image [13]. A problem is set to construct
LCT  L on the basis of the initial TS (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ) array and determine the values of its
structural parameters p (i.e. F (L( p, xi ), f R ( xi ))  opt ).
      </p>
      <p>3</p>
    </sec>
    <sec id="sec-3">
      <title>Literature review</title>
      <p>Present study continues a cycle of works dedicated to the problem of the tree-like
recognition schemes and the discrete object logic classification methods and
algorithms [3, 7–13]. They deal with the issues of constructing, analyzing and optimizing
the logic classification trees. For instance, it is known [14] that the resulting
classification rule (scheme) constructed by the arbitrary method or by the branched attribute
selection algorithm has a tree-like logic structure. The logic tree consists of the
vertices (attributes) grouped in layers that are obtained at a certain step (stage) of the
recognition tree construction [15–17]. The problem of synthesizing the recognition trees
that will be represented by the algorithm tree (graph) is an important one, according to
Ref. [18–21]. Unlike the available methods, the main peculiarity of the tree-like
recognition systems is that the importance of certain attributes (attribute groups or
algorithms) is determined with respect to the function that defines the object partition into
the classes [22]. For instance, in Ref. [23], the case of the decision tree construction
for a set of low-informative attributes is considered.</p>
      <p>The ability of the LCT to execute one-dimensional branching to analyze the
influence (importance, quality) of certain variables gives a possibility to work with the
different-type variables in a form of predicates (while in case of the algorithmic
classification trees (ACT) the relevant autonomous classification/recognition algorithms
shall be applied) [24, 25]. Such a logic tree concept is being used actively in the
intellectual data analysis, where the target goal is to synthesize a model that shall predict
the value of the target variable on the basis of a set of initial data at the system input
[26]. Since the principal idea of the branched attribute selection methods and
algorithms could be defined as the optimal approximation of a certain initial TS by a set of
elementary attributes (the object attributes), then their central problem, i.e. the issue
of selecting an efficient branching criterion (vertices, attributes and discrete object
attributes) comes on line [27–29]. The work [17] is devoted just to these principal
problems by raising the questions of qualitative estimation of certain discrete
attributes, sets and their fixed combinations. This allows an efficient mechanism of
branching realization to be implemented.</p>
      <p>Note that the absolute majority of known decision tree construction algorithms
belong to the ‘greedy algorithm’ class. In other words, if at a certain stage some vertex
(attribute, node) was selected and used for the initial selection partitioning into the
initial selection subsets, the algorithm fails to return at the next stage to selecting the
other vertex (node) with higher-quality partition indices. This means, in fact, that at
the stage of the logic tree construction it is impossible to determine whether the
selected branching vertex will perform some optimal partition [30, 31] at the final stage.
For instance, at the decision tree synthesis, the issues of choosing the criterion of the
attribute (the LCT vertex), after which the initial TS will begin, the training (the LCT
structure construction) stopping criterion and the logic tree (the LCT sub-tree) branch
withdrawal criterion will remain the central ones [32].</p>
      <p>The logic classification tree structures obtained on the basis of the branched
attribute selection methods are characterized, on the one hand, by the compactedness,
and, on the other hand, by the non-uniformity of the layer filling (rarity) as compared
to the regular trees (the algorithm with a single estimation of the attribute importance
[10]. Note that the issues of convergence of the LCT construction process according
to the elementary attribute selection methods and those of selecting the criterion of the
logic tree synthesis process stopping (e.g. limitation by the logic tree depth or
complexity, the accuracy or the structure error number) still remain important [33]. The
solution of these issues from the viewpoint of a constrained (modified) LCT
construction method shall be presented below.</p>
      <p>Thus, notwithstanding a certain range of problems that arise when constructing
and using the decision trees (the LCT concept in the general sense), one has to fix
their following advantages:
i) the tree-like models are distinguished by a principally fast stage of training the
recognition system;
ii) there exists a possibility to synthesize a manifold of decision rules within the
area, where it is difficult even for a qualified expert to form a set of
recommendations;
iii) synthesis of rules (classification rules, decision rules) in the natural language;
iv) the resulting tree-like model obtained is intuitively understandable;
v) the prediction constructed at the final stage of model operation is characterized
by a high accuracy even as compared to the statistical and neural network
models;
vi) a possibility to construct non-parametric model.</p>
      <p>Hence, taking into account the aforementioned, one may conclude that the
decision tree models together with the neural network approach [22, 34] are an important
and relevant tool for the data structure extensive analysis and presentation.
4</p>
    </sec>
    <sec id="sec-4">
      <title>A concept of training selection data approximation by a set of ranked elementary attributes</title>
      <p>
        Consider some defined general-form (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ) training selection (HS) and a certain
system (set) of elementary attributes for the initial selection array 1 ( x), 2 ( x),..., n ( x) .
Let us introduce the following manifolds:
      </p>
      <p>Gr1,...,rn  {x  G / a1 ( x)  r1,..., an ( x)  rn} .</p>
      <p>Note that the system of manifolds Gr1 ,...,rn is a complete partition of the manifold
G realized by the elementary attributes 1, 2 ,..., n . One has to keep in mind that
some of the manifolds Gr1 ,...,rn</p>
      <p>may be empty.</p>
      <p>Let us set Sr1 ,...,rn</p>
      <p>as the number of entrances into the training selection of the
pairs ( xi , f R ( xi )), (1  i  m) that satisfy condition xi  Gr1 ,...,rn .</p>
      <p>Similarly, we shall set Sr1j,...,rn , ( j  0,1,..., k  1) as the number of entrances
into the training selection of the pairs ( xi , f R ( xi )), (i  1,..., m  m) that satisfy
conditions xi  Gr1,...,rn and f R ( xi )  j .</p>
      <p>Let us introduce the following quantities:
 r1 ,...,rn
 Sr1m,...,rn ;  r1j,...,rn  SSrr11j ,,......,,rrnn ;  r1,...,rn  majx r1j ,...,rn .</p>
      <p>
        for any (i  1,..., m) , then
 r1,...,rn  0
(
        <xref ref-type="bibr" rid="ref3">3</xref>
        )
and
      </p>
      <p>Note that if xi  Gr1,...,rn
 r1j ,...,rn  0 , ( j  0,..., k  1) .</p>
      <p>The  r1,...,rn</p>
      <p>quantity characterizes the frequency of entrances of the members of
sequence x1, x2 ,..., xm into the manifold Gr1,...,rn . The  r1j ,...,rn quantity
characterizes the frequency of the object x belonging to the image (class) H J , provided
x  Gr1,...,rn . It should be noted here that condition x  Gr1,...,rn is equivalent to the</p>
      <p>The  r1,...,rn
elementary attribute one: 1 ( x)  r1, 2 ( x)  r2 ,..., n ( x)  rn .</p>
      <p>quantity characterizes the information efficiency of recognizing the
belonging of x to one of the classes H 0 , H1,..., H k 1 , subject to the basic
condition: x  Gr1,...,rn , certainly.</p>
      <p>Assume that at the next stage x  Gr1,...,rn . Then the question arises, to what of the
classes H 0 , H1,..., H k 1 x could be related. Obviously, x must be related to the
class H l , for which the following relation holds true:</p>
      <p> r1,...,rn  rl1,...,rn ,{0  l  k 1} . (4)</p>
      <p>Note that this relation is a certain final classification rule. It is obvious that the
larger is  r1,...,rn , the higher is its general efficiency.</p>
      <p>As mentioned above, the initial TS is meant a single information that represents
the images H 0 , H1,..., H k 1 . Therefore, the class H l means a manifold of all the
TS pairs ( xi , f R ( xi )) that satisfy the basic relation f R ( xi )  l .</p>
      <p>The mean efficiency of recognizing the images H 0 , H1,..., H k 1 defined by the
TS data with the help of the elementary attributes 1, 2 ,..., n shall be estimated by
the following quantity:
oS (1, 2 ,..., n ) 
r1,...,rn
 r1,...,rn *  r1,...,rn .</p>
      <p>The quantity oS (1, 2 ,..., n ) could be considered the estimate of the TS
approximation by a set of elementary attributes 1, 2 ,..., n . From relation (5), the
following expressions for  r1,...,rn ,  r1j ,...,rn and  r1,...,rn result:
1
k

r1 ,..., rn
 j
r1 ,...,rn
 0 ,</p>
      <p>r1 ,..., rn
0  r1 ,..., rn 1
k 1
 0,  r1j ,...,rn  1;</p>
      <p>j0
 
r1,...,rn  1, (r1,..., rn {0,1}) .</p>
      <p> 1 ;</p>
      <p>From relation (6), the following properties of the quantity oS (1, 2 ,..., n )
resequence x1,..., xm , for which the following relations hold true:
xi  Gr1,...,rn .

  r1,...,rn  b
(5)
(6)
(7)
(8)
sult directly:
1
k
i)
ii)
k</p>
      <p> oS (1, 2 ,..., n )  1 ;
oS (1, 2 ,..., n )  1   r1,...,rn  1;</p>
      <p>Note that the above properties are valid for any r1,..., rn that satisfy relation
i(1  i  m, xi  Gr1,...,rn ) . It follows from the second part of relation (7) that the
set of elementary attributes 1,..., n shall then and only then realize a complete
recognition of images H 0 , H1,..., H k 1 (defined by the initial TS). This means that
the set of elementary attributes will be a test given oS (1, 2 ,..., n )  1 , while
b, (
formula (5) enables one to find such algorithm sets.</p>
      <p>Consider one more important peculiarity of the functional estimation of the set of
elementary attributes with respect to the initial TS. Let us have a certain number
1</p>
      <p> b  1) and let M b be a total number of entrances of the objects xi into the
The above relations represent the recognition efficiency for the objects xi by
means of a certain set of elementary attributes 1,..., n larger than b .</p>
      <sec id="sec-4-1">
        <title>The number  b </title>
        <p>m</p>
        <p>b is a fraction of entrances of the objects xi into the
sem
quence x1,..., xm , for which the recognition efficiency by means of the elementary
attribute set 1,..., n is larger than b .</p>
      </sec>
      <sec id="sec-4-2">
        <title>The number  b is expressed as:</title>
        <p>Note that expression</p>
        <p>means summation over all r1,..., rn that satisfy
rela b </p>
        <p>  r1 ,..., rn .</p>
        <p>r1 ,..., rn  b

r1,...,rn b
1
tion  r1,...,rn  b . Let us assume that oS (1, 2 ,..., n )  c and k
from expression (5) and relation for oS (1, 2 ,..., n )  c , we have:
It results from relation (14) that, if c  1 , then there exists the quantity b
(dependent on c ) that:</p>
      </sec>
    </sec>
    <sec id="sec-5">
      <title>A constrained method of classification tree construction on the basis of elementary attribute selection</title>
      <p>Note that the main idea of the stage-to-stage elementary attribute selection is to
maximize the value of the attribute Wm ( f ) quality [2]. The latter means that such
generalized attribute f</p>
      <p>
        must be found in the logic tree algorithms for the training
selection (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ), for which the value of Wm ( f ) is as large as possible.
      </p>
      <p>It should be noted that the elementary attribute importance (informativeness)
means here the value that could be calculated, as a variant, by the following
functionals [13].</p>
      <p>It should be noted that each LCT vertex (Fig. 1) comprises either certain attribute
(mark)  ij or number mij that belongs to the manifold {0,1,..., k  1} . Since the
vertex containing mij is known as the final LCT vertex, it is also called usually the
logic tree leaf.</p>
      <p>Two guiding lines (arrows) denoted 0 and 1 go out from the vertex with the
attribute  ij . The guiding line 0 corresponds to the value  ij  0 , whereas the guiding
line 1 – to  ij  1 . The logic tree is conditionally divided into the layers (levels), and
the j - th LCT layer contains the corresponding attributes 1j , 2j ,..., .</p>
      <p>Note that all the elementary attributes at all the LCT layers, beginning from the
first one and ending by the n - th one, represent, in fact, the attributes obtained after
the n steps (stages) of the LCT construction. The elementary attributes located at the
n - th layer are those derived, respectively, at the n - th step (stage) of the logic tree
construction process.</p>
      <p>
        Note that such classification tree (Fig. 1) realizes (represents), in fact, some
generalized attribute ( x) defined at the manifold G that takes a value from the manifold
{0,1,..., k  1} . After constructing the attribute fi ( x) , a stage of a check-test begins.
Thus, in the check-test regime, a total number S of all those pairs ( xi , f R ( xi )) from
selection (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ), for which relation f R ( xi )  fi ( x) holds true, is calculated.
S
At the next stage, we have to check condition
  . Here  is a parameter that
m
characterizes the estimate of training efficiency with respect to the current problem
(TS). If this condition is satisfied, the classification tree construction process
terminates, and the generalized attribute
      </p>
      <p>
        fi ( x) represented by the structure tree
(Fig. 1) ensures selection (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ) approximation.
      </p>
      <p>Let us emphasize that such scheme of constructing the logic classification tree has
one principal disadvantage related to the fact that the number of elementary attributes
 ij in the tree increases considerably (here i is the elementary attribute number in
the set, j is that of the attribute location layer). Certainly, such complication of the
resulting classification tree affects negatively the apparatus capabilities of the
recognition system (i.e. memory, processor time).</p>
      <p>To overcome the above negative issues, one may suggest the following
modification of the TS data approximation method using the elementary attribute set.</p>
      <p>Let us fix some positive number Z . Consider a logic tree with structure shown in
Fig. 1 that reflects a certain predicate (generalized attribute) fi ( x) .</p>
      <p>So, at the test stage we calculated a certain number S that occurs in relation
  . Now, besides the number S , for each unfinished path r1r2r3 of the logic
tree (Fig. 1), we calculate also the number Sr1r2r3 , where Sr1r2r3 is a number of all
pairs ( xi , f R ( xi )) from TS that, in fact, belong to the path r1r2r3 and satisfy relation
f R ( xi )  l(r1r2r3 ) . Thus, Sr1r2r3 is a number of all those errors made by a certain
predicate fi ( x) (generalized attribute) represented by the LCT (Fig. 1) on the path
S
m</p>
      <p>At the next step, we choose the number S of such paths (r1r2r3 )1,..., (r1r2r3 )Z ,
for which the number Sr1r2r3</p>
      <p>will be maximal. For example, let Z  3 , and the
following relation holds true: S000  S100  S101  S001  S010  S011 .</p>
      <p>Then the paths 000,100,101</p>
      <p>will be chosen only. The further
construction/selection of vertices (elementary attributes)  r1r2r3
paths only.
will be realized for the above</p>
      <p>We shall call this classification tree scheme a constrained method of the LCT
structure construction, because, according to this scheme, the paths with the maximal
number of errors will continue only.</p>
      <p>It should be noted here that, in case of using the above processes at the end of the
paths r1r2r3 that do not belong to the selected Z paths, the values l(r1r2r3 ) shall be
preserved.</p>
      <p>
        Note that the process of the constrained method of the LCT structure construction
could be applied in case when the initial TS (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ) is not fixed, i.e. when at each process
step a separate selection is made.
      </p>
      <p>6</p>
    </sec>
    <sec id="sec-6">
      <title>Model selection</title>
      <p>Note that the LCT construction scheme suggested above allows one to regulate the
classification tree model complexity or to develop a model with prescribed accuracy.
Here the task of choosing the classification tree model from a set of constructed LCTs
for a certain problem is determined by an array of parameters having an essential
importance with respect to a current applied problem (the TS data set).</p>
      <p>Obviously, in order to compare the LCT models and select a particular one, we
have to distinguish its principal parameters (i.e. the image space dimensionality, the
number of vertices etc) and determine their errors with respect to the array of the
input data.</p>
      <p>It is principally important to consider, at this stage of study, the quality criteria of
obtained information models dependent on the model errors, initial TS data array
capacity (the number of training pairs and the problem attribute space dimensionality)
and the number of the model parameters etc.</p>
      <p>It is apparent that the model errors at the TS and ST data arrays for each of the
classes defined by the initial condition of the current applied problem are critically
important parameters of developed LCT model, and they must be necessarily
minimized.</p>
      <p>Note that reduction of the LCT structure complexity (i.e. the number of attributes
in the LCT structure, the total number of vertices in the LCT model and that of
transitions in the LCT structure), as well as the parameters of the information system total
memory consumption and processor time remain here a principal moment. Thus, a
total integral quality index in the following form:</p>
      <sec id="sec-6-1">
        <title>QMain </title>
      </sec>
      <sec id="sec-6-2">
        <title>FrAll</title>
        <p>VAll   pi
i</p>
        <p> ErAll
 e M All .</p>
        <p>(15)
is an important quality index of constructed model in a form of the classification tree
with the parameters of the LCT model structure being taken into account.</p>
        <p>Note that here the parameter ErAll is a total number of the LCT model errors at
the data arrays of the initial test and training selections, respectively, while M All is a
total capacity of these two data arrays. The FrAll parameter characterizes a number
of vertices in the obtained LCT model with the resulting values f R (RF, i.e. the
classification tree leaves), whereas the VAll parameter is a total number of all the types of
vertices in the LCT model structure. A set of parameters pi is the most important
characteristic of the classification tree to be estimated (the number of elementary
attributes used in the classification tree model, the number of transitions between the
classification tree vertices, layers etc).</p>
        <p>It should be noted that this integral LCT model quality index will take values from
zero to unit. The less is this index, the worse is the quality of the constructed tree, and,
in contrary, the larger is this index, the better the model obtained is.</p>
        <p>7</p>
      </sec>
    </sec>
    <sec id="sec-7">
      <title>Experiments and results</title>
      <p>The suggested constrained method of constructing the LCT models (i.e. the
modified method of elementary attribute selection) has been approved for the problem of
classifying an array of geological data (an autonomous recognition system was
constructed for it on the basis of a tree-like classification model), namely, a problem of
oil-bearing formation separation. The initial parameters of the above applied problem
are listed in the following table.
tions) in the  (1.5 /1) proportion dominated in the training information array, while
the TS itself consisted of 1,250 objects. The constructed recognition system efficiency
was estimated at the test sampling of 240 objects, whereas the ST was a segregated
TS part (consisting of the discrete objects of known classification). The training and
the test selection array data were obtained on the basis of the geological survey on the
territory of Transcarpathian province during the 2001–2011 period.</p>
      <p>A fragment of the principal results of the above experiments (comparative tests of
the LCT model construction methods at the applied problem data array) is presented
in Table 2. The constructed LCT models provided the desired level of accuracy preset
by the problem condition, system response rate and operating memory consumption,
but demonstrated different structural complexity of classification tree and generalized
attribute set construction (in the case of the algorithmic classification tree model [7]).</p>
      <p>Note that estimation of the classification tree model quality suggested here reflects
the basic parameters (characteristics) of classification trees and could be used as the
optimality criterion in the procedure of estimating an arbitrary tree-like recognition
system, for instance, in case of the random LCT construction and selection methods
taken from Ref. [17].</p>
      <p>The constrained method of elementary attribute selection (the modified LCT
construction method) suggested in this work was compared to the complete LCT method,
the algorithm with a single (initial) estimation of the discrete attribute importance and
the algorithmic classification tree method, and has shown, in general, a reasonable
result.</p>
      <p>And, finally, please note that the principal idea of classification tree method on the
basis of the autonomous algorithms in the own structure is to provide the
stage-tostage approximation of the initial TS data array by the selected algorithm set (that is
reflected in the tree construction itself). On the one hand, the ACT structure obtained
is characterized by a high flexibility with respect to the applied problems and a
relatively compact structure of the model itself, while, on the other hand, it requires the
sufficient apparatus costs (i.e. memory and processor time) to save the generalized
attributes (classification rule parameters) and the initial quality estimation of the fixed
classification algorithms in accordance with the TS data. Therefore, as compared to
the ACT concept, the LCT method (i.e. the constrained elementary attribute selection
method) possesses high classification scheme response rate, relatively low apparatus
costs for the tree structure (the data structure) saving and operating and high quality
(regulated complexity) of the discrete object classification.</p>
    </sec>
    <sec id="sec-8">
      <title>Conclusions</title>
      <p>Thus, one may conclude that the problem of the LCT construction automation on
the basis of a constrained method of the TS approximation by a set of elementary
attributes has been solved and the scheme of the classification tree construction with
the prescribed accuracy has been suggested. Present paper analyzes the constrained
method of the LCT model construction that allows the prescribed-accuracy
classification trees to be constructed by regulating the complexity of the scheme under
generation. Such approach enables the optimal structure of the LCT model under
construction to be achieved and provides the necessary and sufficient accuracy of the
classification tree obtained.</p>
      <p>The scientific novelty of the obtained results is that for the first time a simple
constrained method/scheme of the LCT construction has been suggested for the first time
on the basis of selecting the elementary attributes with the permanent estimation of
their importance at each step of classification tree construction with the ability of a
further priority-related construction of the fixed LCT construction blocks. Note that
this method at each branching (LCT generating) step takes into account the influence
of a certain object attribute value on the resulting RF value f R in the classification
tree structure.</p>
      <p>Branching criteria in the LCT structure presented in this paper could be effectively
used not only to estimate the informativeness efficiency of certain elementary
attributes, but to calculate the importance of the attribute sets and combinations as well.
This allows the question of specific features of the LCT model construction for less
informative attributes to be raised [23]. We have also suggested a general integral
index of the LCT model quality that allows the general classification tree
characteristics to be represented effectively. Moreover, it can be used to select the most optimal
LCT in case of the methods of random LCT construction [17].</p>
      <p>The practical merit of the results obtained lies in the fact that suggested
constrained LCT model construction method provides possibility to construct cost-saving
and efficient classification models with prescribed accuracy. This method was
realized in the ORION III system algorithm library to solve different applied
classification problems. The above practical applications have confirmed the performance
ability of the LCT models constructed and software developed. These studies may be
addressed in future towards the further development of the LCT methods,
optimization of the software realizations of the suggested constrained method of the LCT
construction, as well as towards its practical approval for a number of real problems in
the field of classification and recognition.
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