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    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Solving Mathematical Puzzles: a Deep Reasoning Challenge Position Paper</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Federico Chesani</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Paola Mello</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Michela Milano</string-name>
          <email>michela.milanog@unibo.it</email>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>DISI - Universita di Bologna V.le Risorgimento</institution>
          ,
          <addr-line>2, 40136 Bologna</addr-line>
          <country country="IT">Italy</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>This is the era of big-data: high-volume, high-velocity and high-variety information assets are being collected, demanding cost-effective information processing. Analytic techniques primarily based on statistical methods are showing astonishing results, but exhibit also limited reasoning capabilities. On the other end of the spectrum the era of bigreasoning is emerging with next-generation cognitive and autonomous end-to-end solvers. A problem description in terms of text and diagrams is given: problem solvers should automatically understand the problem, identify its components, devise a model, identify a solving technique and nd a solution with no human intervention. We propose a challenge: to design and implement an end-to-end solver for mathematical puzzles able to compete with primary school students. Mathematical puzzles require mathematics to solve them, but also logic, intuition and imagination are essential ingredients, thus calling for an unprecedented integration of many di erent AI techniques.</p>
      </abstract>
      <kwd-group>
        <kwd>Deep Reasoning</kwd>
        <kwd>Arti cial Intelligence</kwd>
        <kwd>Mathematical Puzzles</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>This is the era of big-data: high-volume, high-velocity and high-variety
information assets that demand cost-e ective information processing for enhanced
insight and decision-making. Analytic techniques primarily based on statistical
methods are showing astonishing results, but exhibit also limited reasoning
capabilities. At the same time, we are assisting to a number of achievements in
(almost all) Arti cial Intelligence (AI) related elds, such as Natural Language
Processing (NLP), Image and Video Recognition, Symbolic Reasoning, Neural
Networks, Machine Learning and Data Mining, Query Answering (to cite a few).
The number of achieved results is indeed impressive, and public debates (also
in non-scienti c communities) set on re about the possibilities/risks and the
social and ethical roles of AI in general.</p>
      <p>
        Despite the noteworthy results, the human intervention is still essential in a
number of steps when tackling complex problems with AI tools. For example,
humans intervene in identifying problem components and the hidden knowledge
in the description of the problem. Generally speaking, human intervention is
still required to enable the transition from the description of the problem to a
model and a solution approach. Recently, human intervention in problem solving
has been related to Computational Thinking, that helps with these tasks and
cognitive skills by de ning distinctive problem-solving techniques and general
intellectual practices [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ].
      </p>
      <p>In a long-term vision, however, next-generation arti cial cognitive systems
and robots will be autonomous end-to-end solvers that perform the whole
problemsolving task starting from its description without any human intervention. Such
autonomous intelligent agents will be pro-active and problem-solving driven in
nding the right knowledge representation and encoding for modelling the
problem and reasoning techniques for solving it.</p>
      <p>This long-term vision of Arti cial Intelligence results is still far from being
achieved nowadays (and in the foreseeable future). Nevertheless, we strongly
believe that considering and possibly solving single parts of the problem in a
signi cant case study would be an important step forward, a way of starting a
real-world discussion about the applications, implications and ethics of arti cial
intelligence and a source of inspiration for future arti cial cognitive systems.</p>
      <p>
        Since the dawn of Arti cial Intelligence, challenges have been considered as
a mean to push forward the limit of what computers can do autonomously, and
to measure the level of \intelligence" achieved. Problems and issues have been
identi ed in real-world applications and scenarios, but also thanks to
contributions of visionary researchers like Turing, and from a speci c human activity,
i.e. the ability of playing games. Notably, two recent success in AI have been
about games, and computers winning over human players ( Jeopardy game and
Watson1, Go game and AlphaGO[
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]).
      </p>
      <p>In this paper, we argue for the opportunity of considering the deep reasoning
challenge, where next-generation cognitive and autonomous end-to-end solvers
will be able to deal with problems with no human intervention. A problem
description in terms of text and diagrams is given: the end-to-end problem solver
should automatically understand the problem, identify its components, devise
a model, identify a solving technique and nd a solution. To better clarify the
deep reasoning challenge, we ground it on a (simple to be described) goal:
By the middle of the 21st century, (a team of ) fully autonomous
agent(s) shall win a mathematical puzzle competition against
primary school students, winners of the most recent
competitions.</p>
      <p>Mathematical puzzles are an integral part of recreational mathematics and in
general are played by humans. They have speci c rules as multi-player games
have, but they do not usually involve competition between two or more
players. Instead, one must nd a solution that satis es the given conditions. Puzzles
1 http://www.ibm.com/smarterplanet/us/en/ibmwatson/
are described by text and images: to solve them, a human player uses
understanding and intuition, as well as common sense, simple logical and
mathematical/geometry knowledge, causal relations, and many others reasoning-related
capabilities. The focus is on deep reasoning featuring (a) the extraction of
comprehensive knowledge from multi-modal descriptions (texts, pictures and images,
sound and speech, gesture, etc.); (b) the ability of determining both the proper
model and the corresponding reasoning capability; and (c) the capability of
effectively solving the problem (possibly with a feedback from/to the two previous
steps). Moreover, being usually played by humans, mathematical puzzles involve
small quantity of data.
2</p>
    </sec>
    <sec id="sec-2">
      <title>Inside the Deep Reasoning Challenge</title>
      <p>In a computer-aided problem solving process, there is always a substantial
human intervention that enables the encoding of a problem described by text and
diagrams in a model and a solution algorithm. Human intervention is essential
for identifying problem components (decision variables, constraints, logical
relations, objective functions), and the hidden knowledge in the description of the
problem. Usually, a domain expert reads the text and diagrams of the problem,
he/she decides the modelling and solving approach based on his/her experience,
and frames the model. At this point, an automatic problem solving procedure
completes the jobs producing one or many solutions if they exist2.</p>
      <p>A road to achieve deep reasoning could consist of gradually removing the
human intervention and let the computer perform the whole task autonomously.
Possible steps for automatic problem solving could be the following ones:
1. Read and \understand" relevant text and diagrams of a mathematical puzzle.
2. Identify relevant components/sub-problems the original problem can be
decomposed in.
3. Identify a modelling and solving technique(e.g., logic and resolution,
constraint satisfaction, planning, mathematical equations, heuristic search).
4. Identify problem components and hidden knowledge, and suitable encodings
(possibly guided by the chosen modelling technique).
5. Frame the problem model - represent the original problem and its
components by means of an equivalent, machine-understandable model, suitable
for reasoning.
6. Solve the problem - by running an automated problem solving procedure.
For the sake of understanding, we introduce these steps as sequential and
consecutive. However, it is a matter of discussion if they are in the right order, if
there should be one or more iterations, and how much each step in uences the
other ones.</p>
      <p>
        These steps resemble those proposed in 1945 by the mathematician George
Polya in \How to Solve It", and then addressed by Minsky[
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. Moreover, they can
2 Note that in mathematical puzzles the solution always exists and it is unique.
be related to the four key techniques of Computational Thinking: de-composition
- i.e. breaking down a complex problem or system into smaller, more
manageable parts; pattern recognition - i.e. looking for similarities among and within
problems; abstraction - i.e. focusing on the important information only, ignoring
irrelevant detail; and algorithms, that is substituted here with the more general
terms problem solving or inference engine peculiar of AI applications.
      </p>
      <p>
        Hence, in our context, Computational Thinking becomes the more general
process of Arti cial Intelligence Thinking:
\AI thinking is concerned with frameworks, skill sets, and general tools
that are distilled from AI research and practice and are of general interest
to everyone, not just AI researchers. Compared against computational
thinking, AI thinking goes beyond the logic- and algorithm-based
perspectives and should emphasize items such as how to leverage knowledge
bases and case bases in problem solving, capture and reason about
common sense, enable processing of semantics and contexts, and deal with
unstructured data, among others". [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ]
      </p>
      <p>
        To make our challenge more practical, we propose the following few examples.
Example 1: A confused bank teller. A confused bank teller transposed the dollars
and cents when he cashed a check for Ms Smith, giving her dollars instead of
cents and cents instead of dollars. After buying a newspaper for 50 cents, Ms
Smith noticed that she had left exactly three times as much as the original check.
What was the amount of the check?
Example 2: Triangles. How many triangles are in Figure 1?
Example 3: Knights and Knaves (from [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ]). In a village there are two inhabitants
Frank and Jacob. Either Frank is a knight, or Frank is a knave. Either Jacob
is a knight, or Jacob is a knave. Knights always say the truth. Knaves always
say the false. Frank says that Frank is a knave, or Jacob is a knight. Is Frank a
knight or a knave? Is Jacob a knight or a knave?
      </p>
      <p>Apparently there is no common feature underlying these problems, but they
certainly require skills as natural language understanding, diagram
understanding, basic mathematical knowledge, hidden knowledge discovery, common sense
knowledge identi cation (1 dollar corresponds to 100 cents), problem modelling
and solving capabilities. Example 1 can be addressed by means of Constraint
Programming techniques, while Example 3 would call for some logic formalism
and a corresponding procedure (e.g., propositional logic and resolution).
Example 2 instead would call for a tight integration between text understanding and
image recognition algorithms.</p>
      <p>One cornerstone of the challenge is that these skills should be problem-solving
driven. The fact that a bank teller is confused, the name of Ms Smith and the
newspaper bought do not help the solution process and should be discarded. The
fact that we are talking about the two inhabitants, Jacob and Frank, does not
play any important role in the problem solving activity. They could be as well
two friends, students or anything else without changing the problem model. This
requires a paradigm shift with respect to traditional natural language processing
techniques that try to extract contextual knowledge for every word in the phrase.</p>
      <p>Notice also that, even if Figure 1 is quite easy to understand (at least from
a human viewpoint), this is not generally true. Accompanying pictures could
require a deeper understanding, and the same holds for the textual part. From a
computer perspective, shape recognition algorithms could easily achieve the
correct answer. However, deep reasoning would call here for the right mix between
natural language processing and image recognition.
3</p>
    </sec>
    <sec id="sec-3">
      <title>Discussion</title>
      <p>
        A number of similar challenges have been proposed. In the context of the Aristo
Project, a challenge [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ] has been proposed, with the goal of having the computer
pass elementary school math and science exams. Natural language
comprehension, as well as images and pictures understanding are required as fundamental
steps, together with some form of inference and algebraic/mathematical solving
techniques. The Euclid project [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] is investigating the fundamental steps to
automatically solve geometric problems. These challenges have a strict relation to our
proposed notion of deep reasoning, but they mainly focus to provide end-to-end
problem solvers stuck to one speci c solution method (e.g., mathematical
equations, logic), within well-speci ed domains (such as geometry problems). Deep
reasoning should be able to cope with problems described through a number of
diverse input media (natural language, still images, diagrams, moving pictures,
and sounds) and, more fundamental, it should comprise also the choice of the
solution method, as well as the choice of the proper problem model.
      </p>
      <p>
        Given the breath and the complexity of the challenge, the reader might
question if it has the right \size" to foster research advances w.r.t. existing
state-ofthe-art solutions. An important feature of research challenges is the possibility
of facing them is a stepwise fashion, thus providing short-term goals, as well as
long-term ones. The proposed challenge o ers a number of di erent intermediate
steps: for example, we could approach problems at increasing complexity levels.
Moreover, we could focus on problem solvable with a single technique, and then
moving towards the use of an ensemble of techniques. Also, in the beginning
human collaboration might be envisaged as well, fostering a research direction
on how this collaboration could be achieved, as proposed in [
        <xref ref-type="bibr" rid="ref3 ref4">4, 3</xref>
        ]. A further
research question would be on how to measure the advancements: the number of
correctly solved puzzles, the quality of the solution, the required time, and the
autonomy level, are all dimension that would provide measurable outcomes.
      </p>
      <p>We are aware that the proposed challenge is hard and of di cult solution
nowadays, but we strongly believe that even studying and solving only single
parts of the problem would be an important step forward, and a source of
inspiration for future Arti cial Intelligence researches and applications. In addition,
on the road to autonomy, it would be interesting to study which level of human
intervention and interaction with the machine are needed to e ectively
collaborate to solve the problem.</p>
    </sec>
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