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<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>A Neuro-symbolic Approach to Argument Comparison in Structured Argumentation</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Damián Ariel Furman</string-name>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Stephanie Anneris Malvicini</string-name>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Maria Vanina Martinez</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Paulo Shakarian</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Gerardo Ignacio Simari</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Yamil Osvaldo Soto</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Arizona State University</institution>
          ,
          <addr-line>Tempe, AZ</addr-line>
          ,
          <country country="US">United States of America</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Artificial Intelligence Research Institute (IIIA-CSIC)</institution>
          ,
          <addr-line>Carrer de Can Planas, Barcelona, Catalonia</addr-line>
          ,
          <country country="ES">Spain</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires</institution>
          ,
          <addr-line>Intendente Güiraldes 2160, Ciudad Universitaria, Buenos Aires</addr-line>
          ,
          <country country="AR">Argentina</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>Defeasible Logic Programming (DeLP) is a structured argumentation formalism that uses a dialectical process to decide between contradictory conclusions. Such conclusions are supported by arguments, which are compared using a comparison criterion, to decide which one prevails in conflict situations. The definition of a formal comparison criterion is a central problem in structured argumentation, which is typically assumed to be provided by the user or knowledge engineer. In this work, we propose an integration between an argumentative approach to defeasible reasoning, such as DeLP, and machine learning models. Concretely, our goal is to train a neural network to learn a comparison criterion between arguments given a training set comprised of pairs of arguments labeled with which one prevails. We conducted several experiments, using a synthetic DeLP program generator, in order to assess the performance of a neural architecture under diferent kinds of DeLP programs. Our results show that under specific circumstances, a comparison criterion for arguments can be successfully learned by data-driven models.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;Structured Argumentation</kwd>
        <kwd>Defeasible Reasoning</kwd>
        <kwd>Defeasible Logic Programming</kwd>
        <kwd>Neuro-symbolic reasoning</kwd>
        <kwd>Neuro-symbolic learning</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        The integration between machine learning and argumentation has received some attention
in the past; though interesting results have been obtained, there are still many aspects to
investigate; for a survey of works on this subject, see [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. In this work, we focus on combining
neural networks and an argumentative approach to defeasible reasoning. To explain why this
integration is of our interest, we are going to briefly discuss some of the main characteristics of
both parts.
      </p>
      <p>
        Machine learning [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ] is an exciting field that has matured into being capable of delivering
important applications in the recent years after decades of slower progress. Today, much of
the work in areas such as visual processing, language, and speech recognition is at least in part
reliant on machine learning. In particular, neural networks [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ], as a particular machine learning
model, are capable of intrinsic massively parallel processing, which makes them suitable for
several complex domains.
      </p>
      <p>
        On the Knowledge Representation and Reasoning side, defeasible reasoning [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] is, intuitively,
the process of tentatively inferring or deriving logical conclusions from available information—
i.e., since the connection between premises and conclusions is a tentative one, then we can
evaluate the rejection of our conclusions in the presence of information that contradicts them.
In this work, we adopt an argumentative approach to defeasible reasoning, where queries are
analyzed in a dialectical process that exhaustively considers arguments for and against specific
answers in search of warrants, which refers to deciding how available information supports
specific conclusions.
      </p>
      <p>The combination of neural networks and argumentation is attractive because both fields
can benefit from the capabilities of the other. On the one hand, neural networks can improve
the performance of argumentative systems by allowing them to take advantage of available
information (e.g., in real-world datasets) and to adapt to dynamic environments, with high
volumes of data and where answers must be given quickly. On the other hand, argumentation
can help neural networks deal better with inconsistent and incoherent information, can increase
their explanatory power, and can also aid them in expressing specific domain knowledge.</p>
      <p>
        In this work, our goal is to train a neural network to compare arguments and decide which one
prevails in a conflict. For that purpose, we need the network to learn a specific component called
a comparison criterion, which compares two arguments and decides which one prevails. This
can benefit argumentative systems by allowing them to learn a new comparison criterion from
examples, in a dynamic way and relevant to the particular situations that diferent programs
aim to deal with. In general, it is not always simple to define a comparison criterion that fits
the complexity of arguments in a given domain, so this task is often assumed to be carried out
by a knowledge engineer. An approach like ours can therefore improve the performance of
argumentative systems, for example in legal reasoning, where they could learn from datasets
related to jurisprudence. While prior work on the integration of neural and symbolic AI
architectures has introduced parameterized constants [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ] and parameterized operators [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ], we
believe this is the first time a comparison criterion has been parameterized, thus advancing the
eforts in the field.
      </p>
      <p>Our two main hypotheses for this preliminary work are:
1. A neural network can learn a comparison criterion and decide, given two arguments,
which one is preferred (if any), and
2. the complexity of the comparison criterion and the generated programs, and the number
of examples afect the performance of the network.</p>
      <p>This work is organized as follows. In Section 2 we review some basic concepts about the
argumentation formalism that we use, called Defeasible Logic Programming (DeLP). In Section 3
we describe several aspects about the approach taken to arrive at an adequate neural encoding
of arguments. Results obtained from the experimentation are shown in Section 4. In Section 5
we discuss related work, and finally, we summarize our main results and describe future lines
of research in Section 6.</p>
    </sec>
    <sec id="sec-2">
      <title>2. Background</title>
      <p>
        We now recall some basic concepts on Defeasible Logic Programming, which from now on we
refer to as DeLP for short; for the full details of the formalism, we refer the reader to [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
      </p>
      <sec id="sec-2-1">
        <title>2.1. Defeasible Logic Programming (DeLP)</title>
        <p>
          DeLP [
          <xref ref-type="bibr" rid="ref7">7</xref>
          ] is a formalism that combines logic programming and defeasible argumentation. A
DeLP program  = (Π, Λ) is comprised of a set of facts and strict rules (Π), and a set of
defeasible rules (Λ). In this work, we consider an extension of DeLP [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ], called PreDeLP, that
incorporates presumptions, which can be thought of as a kind of defeasible facts.
        </p>
        <p>
          In the following, we briefly recall the most relevant concepts for PreDeLP from [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]. In the
PreDeLP language, a literal  is a ground atom or a negated ground atom. We represent strong
negation with “∼ ” and say that  and ∼  are complementary. A strict rule  (resp., defeasible
rule) has the form:
 ←
1, . . . ,  (resp., L≺− −
        </p>
        <p>L1 , . . . , Ln ),
where  is the head of , and 1, . . . , , with  ⩾ 1, is the body of . Facts are ground literals
representing atomic information. Strict rules represent a strong relation between body and
head . Both facts and strict rules constitute strict (sound) information.</p>
        <p>
          A defeasible rule hea d≺− − body represents a weaker connection between body and head . It
can be understood as expressing that “reasons to believe in the antecedent body provide reasons
to believe in the consequent head ” [
          <xref ref-type="bibr" rid="ref9">9</xref>
          ], but it may be the case that body is true and head is not.
Note that the symbols ← an≺ d− − denote meta-relations between a literal and a set of literals,
and have no interaction with language symbols. As in Logic Programming, strict and defeasible
rules are not conditionals nor implications, they are inference rules [
          <xref ref-type="bibr" rid="ref10 ref7">7, 10</xref>
          ].
        </p>
        <p>A fact (resp., presumption) is a strict (resp., defeasible) rule with an empty body, denoted
with  (resp., L≺− − ). Intuitively, presumptions are defined as pieces of information that are
tentatively taken to be true, usually in the absence of acceptable reasons to the contrary. Since
they express reasons to believe in some information, they represent weaker assertions than facts.
Definition 1 (PreDeLP). A PreDeLP program  , denoted with (Ω, Θ, Δ, Φ), is a set of strict
rules Ω, facts Θ, defeasible rules Δ, and presumptions Φ.</p>
        <p>
          Next, we introduce the concept of annotated derivation, or just derivation, where we adopt
the definition given in [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ].
        </p>
        <p>Definition 2. Let  be a PreDeLP program and  a literal. An annotated derivation  of 
from  , consists of a finite sequence of rules, facts, and possibly presumptions [1, . . . , ], where
 is
1. a fact ,
2. a presumption , or
3. the head of the rule . Furthermore, if a rule  is in the sequence, then its body 1, . . . , ,
is such that for all  , with 1 ⩽  ⩽ ,  is a fact, a presumption or it appears as the head
, for some rule  with 1 ⩽  &lt; .</p>
        <p>A derivation  is strict when neither presumptions nor defeasible rules occur in ; otherwise,
 is defeasible. A literal  is strictly derived from  , denoted  ⊢ , if there exists a strict
derivation for  from  ; on the other hand,  is defeasibly derived from  , denoted  |∼ , if
there exists a defeasible derivation for  from  and no strict derivation exists. A derivation 
for  is minimal if no proper sub-derivation ′ of  ( i.e.,  subsumes ′) is also a derivation
of . Considering minimal derivations avoids the insertion of unnecessary elements that will
weaken its ability to support the conclusion by possibly introducing needless points of conflict.
Given a derivation  for , there exists at least one minimal sub-derivation ′ for .</p>
        <p>A PreDeLP program  = (Ω, Θ, Δ, Φ) is contradictory if there exist derivations for two
complementary literals. We denote with Π = (Ω, Θ) the strict part of  , and assume that the
sub-program Π is non-contradictory. Two literals 1 and 2 disagree w.r.t.  if Π ∪ {1, 2} is
contradictory.</p>
        <p>Queries and Arguments. A query is issued to a program  = (Ω, Θ, Δ, Φ) in the form
of a ground literal  . The dialectical process used in deciding if  is warranted involves the
construction and evaluation of arguments that either support or interfere with the query.
Definition 3. Given a program  = (Ω, Θ, Δ, Φ), let  be a ground literal, and  a derivation
for  obtained from  . An argument for  constructed from  , denoted with ⟨,  ⟩, is the set of
facts, presumptions, and rules (strict and defeasible) used in the derivation .</p>
        <p>Thus, we have that an argument ⟨,  ⟩ is a minimal non-contradictory set of facts,
presumptions, and rules, strict and defeasible, contained in  .</p>
        <p>Given a program  , a literal  is warranted if and only if there exists a non-defeated argument
⟨,  ⟩ supporting  . In order to establish whether ⟨,  ⟩ is a non-defeated argument, defeaters
for ⟨,  ⟩ are considered, i.e., counterarguments that by some criterion are preferred to ⟨,  ⟩.
An argument ⟨,  ⟩ is a counterargument for ⟨ℬ,  ⟩ if and only if ⟨,  ⟩ ∪ ⟨ℬ,  ⟩ ∪ Π is
contradictory. Given a preference criterion ≻ , an argument ⟨,  ⟩ is called a proper defeater of
an argument ⟨ℬ,  ⟩ if it is preferred to ⟨ℬ,  ⟩ according to ≻ , or is called a blocking defeater of
⟨ℬ,  ⟩ if it is equally preferred or is incomparable with ⟨ℬ,  ⟩ according to ≻ . In both cases,
⟨,  ⟩ defeat ⟨ℬ,  ⟩. Figure 1 shows an example where an argument ⟨,  ⟩ is, according to an
unspecified comparison criterion ≻ , a proper defeater of argument ⟨ℬ, ∼  ⟩.</p>
        <p>
          The dialectical analysis that DeLP carries out to decide if an atom is warranted is outside the
scope of this paper; we discuss the main points, and refer the reader to [
          <xref ref-type="bibr" rid="ref7">7</xref>
          ] for more details. Since
there may be several defeaters for an argument, many acceptable argumentation lines could arise
from one argument, leading to a tree structure. An argumentation line  = [0, 1, ..., ] is a
sequence of arguments in which every element of the sequence is a defeater of its predecessor
(except for the rfist argument). A dialectical tree provides a structure for considering all possible
acceptable argumentation lines that can be generated for deciding whether an argument is
defeated (each path from the root to a leaf corresponds to a diferent acceptable argumentation
line). This is called a dialectical tree because it represents an exhaustive dialectical analysis for
the argument at its root.
        </p>
        <p>Given a literal  and an argument ⟨,  ⟩ from a program  , to decide whether  is warranted,
every node in the tree  (⟨,  ⟩) is recursively marked as  (defeated) or  (undefeated),
obtaining a marked dialectical tree  ′(⟨,  ⟩) where:
1. All leaves in  ′(⟨,  ⟩) are marked as  ; and
2. let  be an inner node of  ′(⟨,  ⟩); then,  is marked as  if and only if every child
of  is marked as , i.e., all defeaters of  are defeated.</p>
        <p>Thus, node  is marked as  if and only if it has at least one child marked as  , i.e., at least
one defeater of  is not defeated. Given an argument ⟨,  ⟩ obtained from  , if the root of
 ′(⟨,  ⟩) is marked as  , then  ′(⟨,  ⟩) warrants  , and  is warranted from  .</p>
        <p>Given a DeLP program  , a query  returns one of the following four possible answers: YES
if  is warranted from  , NO if the complement of  is warranted from  , UNDECIDED if
neither  nor its complement are warranted from  , or UNKNOWN if  is not in the language
of the program  .</p>
      </sec>
      <sec id="sec-2-2">
        <title>2.2. Comparison Criteria</title>
        <p>
          As mentioned above, when two arguments attack each other, we must analyze which one
prevails. Given an argument ⟨,  ⟩ and a counter-argument ⟨ℬ,  ⟩, a comparison criterion is
used to determine if ⟨,  ⟩ is preferred to ⟨ℬ,  ⟩ and, therefore, defeats ⟨ℬ,  ⟩. The definition
of such a formal criterion is a central problem in structured argumentation, i.e., in those systems
where the defeat relation must be computed from the structure of arguments. Although the
comparison criterion used in DeLP is modular, the default one is Generalized Specificity [
          <xref ref-type="bibr" rid="ref11 ref9">9, 11</xref>
          ].
This criterion, intuitively, favors arguments with greater information content (classic specificity)
or with less use of rules (a more direct derivation)—in other words, an argument is deemed
better than another if it is more precise or more concise.
        </p>
        <p>
          In the presence of presumptions, Generalized Specificity does not always have the intended
results; for that reason, other preference criteria have been developed, such as
Presumptionenabled Specificity [
          <xref ref-type="bibr" rid="ref8">8</xref>
          ]. According to this criterion, the accumulation of presumptive information
in an argument weakens both the argument itself and its conclusion, meaning that given two
presumptive arguments, if one uses a subset of the presumptions used by the other one, the
former is considered to be a better argument. Figure 2 shows a simple example of the use of
each criterion.
        </p>
        <p>
          Towards other types of comparison criteria. The criteria discussed above are examples
of domain-independent argument comparison criteria; however, in real life applications it
may be necessary to introduce a criterion that depends on the particular domain and usage of
information. In [
          <xref ref-type="bibr" rid="ref7">7</xref>
          ], an alternative general criterion is proposed assuming it is possible to elicit
a preference order among the set of defeasible rules in the program, which is later lifted to a
preference order among arguments that can be built from it.
        </p>
        <p>
          In [
          <xref ref-type="bibr" rid="ref12">12</xref>
          ], an approach to handle multiple argument preference criteria is proposed in the
setting of argumentation-based recommender systems using DeLP as the underlying knowledge
representation and reasoning framework. The proposal allows to change the criterion that can
be used in the comparison process, and even to use several criteria simultaneously that can
be combined through adequate operators. Nevertheless, establishing which criteria should be
used, and determining whether it needs to change over time, is not a trivial task. In the next
section, we develop our proposal that seeks to learn domain (or application) specific criteria
using neural networks.
        </p>
      </sec>
    </sec>
    <sec id="sec-3">
      <title>3. Training a Neural Network to Compare Arguments</title>
      <sec id="sec-3-1">
        <title>3.1. General Overview</title>
        <p>
          Our methodology for training neural network models is comprised of three steps. First, we
use a synthetic DeLP program generator [
          <xref ref-type="bibr" rid="ref13">13</xref>
          ] to produce a set of programs. Then, for each
generated program, and using a DeLP solver [
          <xref ref-type="bibr" rid="ref10 ref14">10, 14</xref>
          ], we generate a list of pairs of arguments
compared during the inference process indicating which one was chosen by the solver as a
defeater. Finally, we train the neural network, having as input the pairs of arguments and a
scalar as output, indicating which argument is preferred (or if neither is, which occurs in the
        </p>
        <sec id="sec-3-1-1">
          <title>DeLP program</title>
        </sec>
        <sec id="sec-3-1-2">
          <title>DeLP Solver</title>
        </sec>
        <sec id="sec-3-1-3">
          <title>Neural</title>
        </sec>
        <sec id="sec-3-1-4">
          <title>Network</title>
          <p>Argument
pairs
Defeater</p>
        </sec>
        <sec id="sec-3-1-5">
          <title>Dialectical tree</title>
          <p>case of blocking defeaters).</p>
          <p>Figure 3 illustrates our vision of how a neural network and the DeLP solver can be integrated,
where the former is trained to learn a criterion and carry out the comparison between arguments,
while the latter carries out the dialectical analysis.</p>
        </sec>
      </sec>
      <sec id="sec-3-2">
        <title>3.2. Synthetic Program Generation and Experimental Settings</title>
        <p>For the programs obtained from the DeLP generator, we consider two criteria: Generalized
Specificity and Presumption-enabled Specificity . In addition, we explored two types of program
settings: complexity (simple or complex programs) and the presence of blocking defeaters. The
complexity of programs depends mainly on the following parameters:
• MAX_BODYSIZE (sets the highest value in the average length of the defeasible derivation
of any argument),
• MIN_ARGSLEVEL (sets the number of dialectical trees),
• RAMIFICATION (sets the number of argumentation lines), and
• TREE_HEIGHT (sets the length of argumentation lines).</p>
        <p>
          We suggest the reader to see [
          <xref ref-type="bibr" rid="ref13">13</xref>
          ] for more details on the synthetic DeLP program generating
processes. The presence of blocking defeaters indicates whether or not they are considered
when generating the pairs of arguments to be compared.
        </p>
        <p>For each setting combination, three datasets were generated with diferent sizes: 200, 500,
and 1000 programs. Table 1 shows the average number of argument pairs per program based
on the program configuration described above.</p>
      </sec>
      <sec id="sec-3-3">
        <title>3.3. Encoding Arguments</title>
        <p>In order to be amenable to neural training methods, we need to develop a vector encoding of
arguments obtained from DeLP programs, where the encoding is done in such a way that the
connection between internal components is adequately represented.</p>
        <p>Complexity</p>
        <p>Simple
Simple
Complex
Complex</p>
        <p>Blocking
×
✓
×
✓
#Argument pairs per program
9.63
18.80
57.07
243.52</p>
        <p>The network input is constructed by encoding a pair of conflicting arguments into a single
tensor, with the following conventions (illustrated in Figure 4):
• Value “1” is used to represent defeasible rules, while “− 1” is used to represent strict rules.
• Each atom is represented with an id consisting of an integer value strictly greater than 2.</p>
        <p>The same integer will be used to represent the same atom in the context of a pair of
conflicting arguments. The negation of an atom is represented by the negative counterpart
of the number representing that atom.
• Rules and atoms are separated using “2”, while arguments are separated using value“− 2”.
• Arguments have a fixed length so if the representation of the argument is smaller than
that fixed length, zeros are used to fill the unused space and the neural network ignores
them.
• For the output, we have three possible values:
– 0 if the first argument is preferred over the second one,
– 1 if the second argument is preferred over the first one, and
– 2 if no argument is preferred over the other, i.e., the arguments are blocking defeaters.</p>
        <p>As mentioned, we developed this encoding because it maintains the relationship between
the inner components of the arguments, and it allows each argument to be represented as a
tensor of the same length. Algorithms 1 and 2 describe the full processes of encoding a single
argument and the construction of the input, respectively.</p>
        <p>The following example shows how a pair of conflicting arguments are encoded and how the
input is built from both encodings. Figure 4 provides a graphical illustration of the example.
Example 1. Let ⟨, 8⟩ and ⟨ℬ, ∼ 8⟩ be two conflicting arguments.</p>
        <p>In this case, literal 8 is represented with value 7, 0 with 8, and 9 with 9, while 8 is represented
with − 7. The symbo l≺− “ − ” is represented with value 1, while − 1 is used after the value 8 to indicate
that 0 is a fact. Rules are separated from facts and presumptions using the value 2, and both
arguments are concatenated on the final input vector adding a value of − 2 in between.
⟨, 8⟩
Encoding of ⟨, 8⟩
: [(a 8≺− − a0 ), 0]
: [7, 1, 8, 2, 8, − 1, 0, ..., 0]
⟨ℬ, ∼ 8⟩ : [(∼ a 8≺− − d9 ), (d 9≺− − true)]</p>
        <p>Encoding of ⟨ℬ, ∼ 8⟩ : [− 7, 1, 9, 2, 9, 1, 0, ..., 0]
8 -1
Argument 1</p>
        <p>Argument separator</p>
        <p>Argument 2
7
1
8
2
encodedArgument ← [ ]
for each element in Argument do
encodedHead ←
encodedArgument .append (encodedHead )</p>
        <p>LiteralToInteger (element .head )
if element .isFact or element .isStrictRule then</p>
        <p>encodedRuleType ← − 1
else</p>
        <p>encodedRuleType ← 1
encodedArgument .append (encodedRuleType)
for each literal in element .body do</p>
        <p>encodedArgument .append (LiteralToInteger (literal ))
if element is not Argument .last then</p>
        <p>encodedArgument .append (2)
return encodedArgument
For the output, the value 0 represents that ⟨, 8⟩ defeats ⟨ℬ, ∼ 8⟩:</p>
        <p>Input : [7, 1, 8, 2, 8, − 1, 0, ..., 0, − 2, − 7, 1, 9, 2, 9, 1, 0, ..., 0]</p>
        <p>Output : 0</p>
        <p>After presenting the neural encoding, in the next section we discuss the neural architecture
proposed and used in our empirical evaluuation.</p>
      </sec>
      <sec id="sec-3-4">
        <title>3.4. Neural Network Architecture</title>
        <p>For this preliminary proposal, we used a simple neural network architecture with 3, 000
parameters (10 linear, fully connected hidden layers with 300 nodes each). The output of the neural
Algorithm 2: EncodeNetworkInput</p>
        <p>Input: Argument1 , Argument2
encodedArgument1 ←</p>
        <p>EncodeArgument (Argument1 )
encodedArgument2 ←</p>
        <p>FillToMaxLength(encodedArgument1 )</p>
        <p>EncodeArgument (Argument2 )
input ←
input .append (− 2)
input .append (FillToMaxLength(encodedArgument2 ))
returNn ienpuutral network training - Datasets
Complexity
e
l
p
m
i
S
x
e
l
p
m
o
C</p>
        <p>Blocking defeaters
Blocking defeaters
s
e
Y
o
N
s
e
Y
o
N</p>
        <p>Presumptions
Presumptions
Presumptions
Presumptions
s
e
Y
o
N
s
e
Y
o
N
s
e
Y
o
N
s
e
Y
o
N</p>
        <p>Amount of programs
Amount of programs
Amount of programs
Amount of programs
Amount of programs
Amount of programs
Amount of programs
Amount of programs
network depends on the characteristics of the arguments being processed:
In the next section, we discuss the details of our experimental evaluation using this setup.</p>
      </sec>
    </sec>
    <sec id="sec-4">
      <title>4. Experimental Evaluation</title>
      <p>Dataset. Diferent datasets were created combining all possible values of the following settings:
with single or complex programs, with or without blocking defeaters, using Presumption-enabled
1</p>
      <p>Specificity or Generalized Specificity, and the number of programs from which arguments were
extracted. Figure 5 shows an overview of the diferent datasets considered.</p>
      <p>Experimental Setup. For each dataset, a 3-fold cross-validation was done by training three
networks with three diferent random partitions of train and test, respecting a proportion of
80% and 20% respectively.</p>
      <p>Results. Figures 6 and 7 show the average Accuracy, Precision, Recall, and F1 scores of the
three models along with the standard deviation of the F1 scores for both criteria.</p>
      <p>Our results show that a simple neural network architecture with 3, 000 parameters can obtain
close to perfect performance in learning two diferent comparison criteria for arguments of
DeLP programs of varying complexity with only proper defeaters by analyzing examples of
argument comparisons. If programs have also blocking defeaters, performance is still very good:
models achieve high accuracy, precision, recall, and F1 score for datasets generated from simple
programs and good accuracy score also for complex programs, though precision, recall, and F1
scores drop, indicating a bias towards the majority class, the blocking defeaters.</p>
      <p>Larger datasets created with more programs perform slightly better. Although the
improvement is in general very small, it was consistent in all our experiments. Complex programs have
worse performance than simple programs only in the presence of blocking defeaters and/or
presumptions. Finally, the large diference in performance between blocking and non-blocking
datasets could be explained because of the diferent types of classification done while training
with them, using binary vs. multi-class classification.</p>
    </sec>
    <sec id="sec-5">
      <title>5. Related Work</title>
      <p>
        In general terms, this work falls within the area known as Neuro Symbolic Artificial Intelligence
(NeSy AI) [
        <xref ref-type="bibr" rid="ref15 ref16">15, 16</xref>
        ], a rich field that encompasses the combination of deep neural networks with
symbolic logic for reasoning and learning. Currently, NeSy AI frameworks are capable of
carrying out a variety of tasks such as incorporating prior knowledge into deep learning architectures,
guiding the learning process with logical constraints, providing symbolic explainability, and
using gradient-based approaches to learn logical statements.
      </p>
      <p>
        More specifically, this paper focuses on Argumentation and Machine Learning, an area that
aims to integrate the advantages of both fields to address their limitations (for a survey, see [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]).
These two fields can greatly benefit from each other: argumentation can improve machine
learning in several ways, e.g., by providing it with explainability [
        <xref ref-type="bibr" rid="ref17 ref18">17, 18</xref>
        ], and machine learning
can aid argumentation by building arguments from real data, as in argument mining [
        <xref ref-type="bibr" rid="ref19 ref20">19, 20</xref>
        ]. The
integration of argumentation and machine learning has been proven to be fruitful in diferent
domains, like social network analysis [
        <xref ref-type="bibr" rid="ref21">21</xref>
        ], healthcare [
        <xref ref-type="bibr" rid="ref17 ref22">22, 17</xref>
        ], law [
        <xref ref-type="bibr" rid="ref22 ref23">23, 22</xref>
        ], and security [
        <xref ref-type="bibr" rid="ref24 ref25">24, 25</xref>
        ].
      </p>
      <p>
        Finally, the following line of work is closely related to our own, though it is essentially
diferent in spirit. In [
        <xref ref-type="bibr" rid="ref26">26</xref>
        ] an algorithm for translating an agent’s knowledge base, expressed
as an ODeLP rule base, into a Perceptron-based neural network is introduced. In [
        <xref ref-type="bibr" rid="ref27 ref28 ref29">27, 28, 29</xref>
        ]
the authors propose combining a set of criteria specified as a DeLP program with a Fuzzy ART
neural network model for solving ambiguities in clustering problems, while [
        <xref ref-type="bibr" rid="ref30">30</xref>
        ] also proposes
to combine a counter-propagation neural network with a DeLP program for filtering HTML
      </p>
    </sec>
    <sec id="sec-6">
      <title>6. Conclusions and Future Work</title>
      <p>DeLP and neural networks are powerful knowledge representation and problem-solving tools
whose combination can be very fruitful. In this preliminary work, we have investigated the
feasibility of training a neural network to learn a comparison criterion, obtaining promising
results not only for proper defeaters but also when including blocking ones. Particularly,
supporting our hypotheses we can say that:
1. Experimental results provide support for Hypothesis 2, since evidence shows that
performance of the neural network is afected when the complexity of the program or the
comparison criterion increases.
2. With respect of the number of examples being used, we can’t confirm that more examples
lead to better performance since we obtained similar results on the experiments with
only proper defeaters, and the experiments with blocking defeaters showed a decrease in
performance with larger datasets.</p>
      <p>
        As future work, we are interested in studying how other, possibly arbitrary and
domaindependent comparison criteria can be learned from data. Towards this end, we are exploring
how we can address the general lack of real-world datasets by deriving rules from text in natural
language, for which we can take advantage of recent developments in Large Language Models
(LLMs). Previous successes in applying DeLP to real-world programs like cyber attribution [
        <xref ref-type="bibr" rid="ref24">24</xref>
        ]
support working in this direction, where instead of relying on knowledge engineering eforts we
might develop general templates that can be instantiated en masse and then, after automatically
deriving sets of arguments, these can be labeled based on available ground truth. It will be
interesting to analyze whether the classical comparison criteria used in this work come up in
such scenarios, or perhaps close variants or entirely new ones arise.
      </p>
      <p>We are also interested in studying possible interactions between the dialectical analysis of
arguments that DeLP carries out and neural computation architectures. Finally, it would be
interesting to explore combining our models with diferent attention mechanisms.</p>
      <sec id="sec-6-1">
        <title>ACKNOWLEDGMENTS</title>
        <p>This work was supported by funds provided by Universidad Nacional del Sur (UNS)
under grants PGI 24/N046 and PGI 24/ZN057), Agencia Nacional de Promoción Científica y
Tecnológica under grants PICT-2018-0475 (PRH-2014-0007) and PICT-2020-SERIEA-01481,
and CONICET under grants PIP 11220200101408CO and PIP 11220170100871CO. The
authors also acknowledge support by the Spanish project PID2022-139835NB-C21 funded by
MCIN/AEI/10.13039/501100011033, MCIN/AEI/ 10.13039/501100011033 and by “European Union
NextGenerationEU/PRTR”.</p>
        <p>
          The authors would like to thank Mario A. Leiva for providing the code for the DeLP program
generator that he developed [
          <xref ref-type="bibr" rid="ref13">13</xref>
          ], and for his help during its deployment in this project.
        </p>
      </sec>
    </sec>
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