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      <title-group>
        <article-title>Beyond Analytical Modeling, Gathering Data to Predict Real Agents' Strategic Interaction</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Rustam Tagiew (tagiew@informatik.tu-freiberg.de)</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Institute for Computer Science of TU Bergakademie Freiberg</institution>
          ,
          <country country="DE">Germany</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>This paper presents research proposals on the interdisciplinary research infrastructure for understanding human reasoning in game-theoretic terms. Strategic reasoning impacts human decision making in social, economical and competitive interactions. The provided introduction summarizes concepts from AI, game theory and psychology. First result is a concept of interdisciplinary game description language as a part of the focused interdisciplinary research infrastructure. The need of this domain-speci c language is motivated and is aimed to accelerate the current developments. As second result, the paper provides a summary of ongoing research and its signi cance.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>Introduction</title>
      <p>Di erent scienti c disciplines predict outcomes of human social, economical and
competitive interactions on the granularity level of individual decisions [1, p.4].
Autonomous intelligent systems, which perceive, decide and act in an
environment according to their preferences, are called agents in AI, MAS and sociology.
People and implemented arti cial agents are called as real agents.</p>
      <p>
        A rational agent makes always decisions, whose execution has according to
his subjective estimation the most preferred consequences for him [
        <xref ref-type="bibr" rid="ref2 ref3">2,3</xref>
        ]. Level of
intelligence impacts the quality of the subjective estimation. Rationality justi es
agents' decisions and predictions of other agents' decisions. In strategic
interactions, agents are rational and apply mutually and even recursively the concept
rationality. Game theory predicts outcomes of strategic interactions [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. Further,
game is a notion [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] for the formal structure of a concrete strategic interaction.
Agents involved in a game are called players.
      </p>
      <p>
        A game in normal form consists of strategies (sets of decisions) and players'
preferences over outcomes [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. Finite normal form games contain a nite number
of outcomes. Game theory is there to provide equilibria id est to solve games.
An equilibrium is an irrevocable combination of players' strategies { none of
the players can improve his outcome by altering his chosen strategy. If players'
preferences are de ned by their payo functions, the equilibria of nite normal
form games are guaranteed [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. A payo or also utility function assigns a numeric
value as magnitude of preference to every outcome. Calculation of equilibria is
generally NP-hard [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. GAMBIT is a software library for this task [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
      </p>
      <p>In the case of players, who are intelligent enough to solve their game, an
equilibrium should (immediately) occur independently of players' builds or even
real identities. This is fundamentally di erent to the common AI approach
(referenced further as game playing), where programs compete the last decades in
playing chess e.g. still without achieving any irrevocable solution [2, chap.5].
Although the existence of an equilibrium is proven for chess, analytical abilities of
none of the present game theorists su ces to show at least, whether the
equilibrium implicates the win of the whites. If at least one of the players is not able
to solve the game, an equilibrium is not guaranteed to occur.</p>
      <p>
        Although the modern game-theoretic textbooks contain mostly ctive
scenarios, the reader is asked to resist the conclusion that real-life cases can not be
formalized as games. Contrary to parlor games, a concrete strategic interaction
with lacking explicit rules is to be formalized as a game. Manual formalization
is not guaranteed to be accurate and mostly results in far too simpli ed \toy
games" as criticized in AI literature [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. Scaling down the space of games can
enable automatic formalization [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ]. A player faces this problem as well as a strict
outsider like a game theorist. He has to answer the question correctly, which
interacting agents really exist in the environment and in what kind of game he
is involved in. It is called incomplete information in game-theoretic terms [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ], if
this question can not be clari ed.
      </p>
      <p>
        Incomplete information transforms to imperfect information, if a
probability distribution over all possible formalizations of a game can be provided [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ].
Poker e.g. is a game of imperfect information, where every player is supposed
to be aware about the probability distribution over the possible hands, but does
not know the current hands. It is not obligatory that a game becomes a common
knowledge (CK) among its players { it is also possible that a player bears his own
variant of the game in mind, he misconceives to be involved in. As a reminder,
CK is that, what everybody knows and everybody knows that everybody knows
it and in nitely prepending \everybody knows that" [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ].
      </p>
      <p>
        CK of the game would not exist during a poker round, if Alice hides cards
in her sleeve unknown to her opponent Bob. Alice considers that Bob's actions
should conform the equilibria calculated in the original game and she calculates
the equilibria of a global game consisting of the original game and the \cheated"
game [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ]. Players may have an intractable number of mutual nested believes
about the details of their game. For instance, Alice could reckon to some extent
that Bob also cheats, Bob could suspect Alice of considering him as a cheater and
so on. An intractable number of mutual nested believes results in an intractable
size of the global game, where no game-theoretic solution is guaranteed to be
calculated or even to exist in the case of in nity. Therefore, cases are
concentrated on, where a game of imperfect information is its players' CK.
      </p>
      <p>
        This paper concentrates on the relevance of strategic reasoning in real agents'
decision making, which causes an (immediately) occurring equilibrium, if the
unbounded intelligence is assumed. In the cases of absent strategic reasoning, game
theory can still predict the direction of convergence id est towards an
equilibrium. This is proposed by Price [
        <xref ref-type="bibr" rid="ref12">12</xref>
        ] for prediction of stochastic processes, more
precisely populations in biological terms, and is called evolutionary game theory
[
        <xref ref-type="bibr" rid="ref13">13</xref>
        ]. A convergence is also observed in the case of using reinforcement learning
instead of strategic reasoning [14, e.g.]. The assumption of this paper is that
the usage of the concept strategic reasoning can be extended by newer methods.
This assumption does not negate the existence of reinforcement learning e.g. in
real agents' strategic interactions and is discussed next in the case of people.
      </p>
      <p>
        Although the real human preferences are a subject of philosophical
discussions [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ], the application of strategic reasoning assumes that they can be
captured in concrete interactions as required for modeling rationality. The
consideration of people as rational agents is disputed at least in psychology [16,
pp.527{530], where even a scienti cally accessible argumentation exposes the
existence of stable and consistent human preferences as a myth [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ]. Since the
last six decades nevertheless, the common scienti c standards for econometric
experiments are that subjects' preferences over outcomes can be insured by
paying di ering amounts of money [
        <xref ref-type="bibr" rid="ref18">18</xref>
        ]. However, insuring preferences by money is
criticized by the term homo economicus as well.
      </p>
      <p>
        The ability of identifying other agents and of modeling their reasoning
corresponds with the psychological term ToM (Theory of Mind) [
        <xref ref-type="bibr" rid="ref19">19</xref>
        ], which lacks
almost only in the cases of autism. For application of strategic reasoning,
subjects as well as researchers, who both are supposed to be non-autistic people,
may be then able of modeling of others' strategic reasoning too. In Wason task
at least, subjects' reasoning does not match the researchers' one though [
        <xref ref-type="bibr" rid="ref20">20</xref>
        ].
People may use no logic at all [
        <xref ref-type="bibr" rid="ref21">21</xref>
        ], but also mistake seriously in the calculus of
probabilities [
        <xref ref-type="bibr" rid="ref22">22</xref>
        ].
      </p>
      <p>
        The data of econometric experiments does not match the equilibria of games
according to which they are conducted [
        <xref ref-type="bibr" rid="ref23 ref24">23,24</xref>
        ]. That means that the strategic
reasoning according to the global (researchers' point of view) game does not
arise among the subjects due to a set of reasons, which should be clari ed.
There is a need for more than only the pure analytical game theory, because
even people familiar with game theory are observed to deviate from equilibria in
multiple cases [
        <xref ref-type="bibr" rid="ref24">24</xref>
        ]. It is gathering and analyzing of data from experiments and
eld studies. This paper steps further { it proves the potential of making the
interdisciplinary research on real agents' strategic interactions more e cient. Like
in bio-informatics [
        <xref ref-type="bibr" rid="ref25">25</xref>
        ], it is supposed to be done by an interdisciplinary research
infrastructure { domain speci c languages and common tools.
      </p>
      <p>The paper is organized as follow. Next section summarizes the main concepts
for the interdisciplinary research infrastructure. Then, the section 3 presents
detailed the hitherto research. At the end, the results are concluded in order to
gure out the remaining construction sites.
2</p>
    </sec>
    <sec id="sec-2">
      <title>Conceptualizing Interdisciplinary Research</title>
    </sec>
    <sec id="sec-3">
      <title>Infrastructure</title>
      <p>A conceptualization of the already partially existing (interdisciplinary) research
infrastructure for real agents' strategic interactions follows. It aims to provide
an elaborate overview and an exhaustive motivation. Arti cial agents are also
included into consideration, although this paper concentrates mostly on people.
People can be replaced by arti cial agents in order to simulate or to intervene
human strategic interactions. Whether simulation or intervention { in both cases,
arti cial agents can cut costs, allow a direct control of their builds, can be
numerously deployed and are almost unlimited in period of use.</p>
      <p>In order to avoid incomplete information, which can make the application of
strategic reasoning intractable, an explicit formalization is to be used. Because
a formalization of a concrete strategic interaction can be inaccurate, it is
reasonable to execute it inversely. A concrete strategic interaction has to be created
out of an already existing game. This is game realization and a software-based
game realization is a game implementation [1, p.108]. Game realization is the
almost always unmentioned action after mechanism design [2, p.632]. Mechanism
design is inverse to game solving { adjusting of a game to already predetermined
desired equilibria. If game realization is impossible, mechanism design is futile.</p>
      <p>
        In real-life cases, games can be realized by physical conditions, by
nonparticipating agents, by participating agents themselves or by a subset of the
3 previous instances [
        <xref ref-type="bibr" rid="ref26">26</xref>
        ]. If participating agents are responsible for a (partial)
game realization, they should prefer the compliance with rules over the
advantages from \cheating". A non-participating agent responsible for game realization
can be modeled as rational too. For instance, the attorney in prisoner's dilemma
keeps his word in order to not risk his reputation, where prisoner's dilemma is
supposed to be familiar to the reader.
      </p>
      <p>
        In the case of game implementation, the software can be divided into
fractions: game management, game-solving algorithms, game-playing algorithms and
auxiliary algorithms. Game management is the part of software, which executes
the rules and calculates outcomes [
        <xref ref-type="bibr" rid="ref27">27</xref>
        ]. It may also record in order to gather data
[
        <xref ref-type="bibr" rid="ref28">28</xref>
        ]. Human-computer interfaces aka proxy agents [
        <xref ref-type="bibr" rid="ref29">29</xref>
        ] are examples of auxiliary
algorithms. Additionally, game implementation minus game-solving/playing
algorithms is called game infrastructure [1, p.53].
      </p>
      <p>
        In the case of explicit rules, the question about the form of games arises.
The normal form is one of the two most general forms to express games in
nonco-operative game theory. In co-operative game theory or also coalitional game
theory [
        <xref ref-type="bibr" rid="ref30">30</xref>
        ], players may covenant and group into coalitions. The process of
negotiating and the way of ensuring the agreements themselves are not issues of
co-operative game theory. From non-co-operative game-theoretic point of view,
disadvantages should arise for the players, who break the agreements. From both
points of view, a player makes a rational decision, whether it is his own behavior
or an agreement about a co-operative behavior. Both points of view are
considered to be equal [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ]. Due to the fact that the pure analytical game theory does
not su ce, the interest is focused a more detailed form { the extensive form {
the second most general to express games in non-co-operative game theory. In
contrast to others, the extensive form captures separately the actions' sequences
and their alternating subsequences in a representation known as game tree in AI.
Therefore, the actions' sequences can be called as root paths. The normal form
and the coalitional formalization are skipped as argued because of their higher
abstraction. Also skipped is the consideration of continuous games [
        <xref ref-type="bibr" rid="ref31">31</xref>
        ], where
equilibra can be acquired by solving of di erential equations and no general form
exit.
      </p>
      <p>The theoretical appropriateness of the extensive form does not result a
computational one { the problem is the inappropriate size of a games represented in
extensive form. For instance, one can consider that the rules of chess are sent
as a game tree via network. It is rather an Interdisciplinary Game Description
Language (IGDL) having expressive power of the extensive form, which is needed
for 4 rough categories of considered instances within and beyond game
implementations. These categories are A) game-solving algorithms, B) game-playing
algorithms, C) non-solving/playing algorithms (game management, mechanism
design, auxiliaries etc.) and D) scienti c human users (sociologists e.g.).</p>
      <p>
        Less important issues are skipped out of this consideration for IGDL { issues
like adjustments for evolutionary mechanism design [
        <xref ref-type="bibr" rid="ref32">32</xref>
        ] and for non-scienti c
human users. Reducing the size compared with an equivalent representation in
extensive form is called further compactness [1, p.65]. Compactness is not the
only criterion for IGDL. For the categories A{D, one can summarize the partial
criteria as following:
1. Computational speed-up. Regularities like symmetries can be used in
order to reduce the computation time of equilibria [
        <xref ref-type="bibr" rid="ref33">33</xref>
        ]. This feature is captured
by formalisms called succinct games and should be also provided by IGDL.
Reduction of computation time by using compact representation applies also
to game-playing algorithms [34, e.g.] and can be considered in the case of
game management.
2. Re-usability &amp; comparability. A language for games forces the re-usability
and also comparability of game-playing algorithms as suggested by Pell [
        <xref ref-type="bibr" rid="ref35">35</xref>
        ].
This applies also for game-solving algorithms [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] and for non-solving/playing
algorithms algorithms [
        <xref ref-type="bibr" rid="ref36">36</xref>
        ].
3. Interdisciplinary human usability. IGDL should prevent the scienti c
manual game-theoretic formalization from resulting in \toy games" as
criticized in AI literature [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. A graphical representation of a game may improve
the usability even more [
        <xref ref-type="bibr" rid="ref37">37</xref>
        ].
4. Decidability. This feature should be provided for IGDL in order to
ensure that the calculation of outcomes de nitely terminates [
        <xref ref-type="bibr" rid="ref38">38</xref>
        ]. This also
important for game-solving/playing algorithms to be able to calculate the
consequences of actions.
5. General compact interchange format. For interfacing instances of the
categories A{D, IGDL should satisfy the need of a compact interchange
format. At same time, IGDL should be as general as possible, where the
facility to express n-person games of imperfect information is most general.
Finally, instances of all the mentioned categories should be at least
theoretically IGDL-compatible in order to skip reformatting, id est to facilitate their
e cient mutual integration.
6. Time. Time remains the issue disregarded by the extensive form. As one
can conceive by comparing game playing in fast chess and in normal chess,
time given for making decisions impacts them. Therefore, time is needed to
be included in IGDL in order to ascertain the time dependent details by
the explicit rules. Otherwise, the durations of actions' sequences e.g. may
depend on the current game implementation and not be given explicitly in
advance conjoined with the game.
      </p>
      <p>
        Some examples for usage of IGDL can be provided. As 1st example,
IGDLcompatible chess playing algorithms can be incorporated into system, which
compete in playing other chess-like games described in IGDL. As 2nd example,
a IGDL-based game editor can be used to allow non-computer scientists to set-up
their own experiments. As 3rd example, data gathered in experiments conducted
according to a game described in IGDL can be compared with the equilibria
calculated by IGDL-based game-solving algorithms for the same game. As 4th
example, game described in IGDL can be easily forwarded to the IGDL-based
game-playing algorithms for an approximative solution, if IGDL-based
gamesolving algorithms fail to output timely. As 5th example (proposed by [
        <xref ref-type="bibr" rid="ref39">39</xref>
        ]), the
data of the experiments conducted based on IGDL can be better compared or
even stored in a central web database like the state of art in bio-informatics.
Games described in a special language with and without conjoined time
dependent details are called further game descriptions.
3
      </p>
    </sec>
    <sec id="sec-4">
      <title>Summarizing Ongoing Research</title>
      <p>IGDL is the desired domain-speci c language, which has already some
precursors and these precursors are summarized in this section. It is also possible that
the ongoing research will bear di erent concurrent versions of IGDL. In order
to assess the hitherto approaches better, a rough categorization of the used
formal means is provided. Such categories are functions, graphs, logic, Petri-nets
and so on. Tab.1 contains the regarded approaches and their rough categories.
The ability to describe simultaneous moves (id est actions) is subset to more
general imperfect information, because other players' actions can be unobserved
only during a simultaneous execution. In deterministic games, it is impossible to
describe a probability distribution over possible subsequences of actions.</p>
      <p>
        In discrete non-co-operative game theory, there are di erent approaches for
compact game forms, whose aim is computational speed-up [
        <xref ref-type="bibr" rid="ref33">33</xref>
        ]. The most
important of them chronologically ordered are congestion games [
        <xref ref-type="bibr" rid="ref40">40</xref>
        ], sequential
form [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ], graph games [
        <xref ref-type="bibr" rid="ref41">41</xref>
        ], local e ect games [
        <xref ref-type="bibr" rid="ref42">42</xref>
        ] and action graph games [
        <xref ref-type="bibr" rid="ref43">43</xref>
        ].
The software GAMUT can generate random games of these and other kinds,
where the extensive form is included [
        <xref ref-type="bibr" rid="ref52">52</xref>
        ]. Computational speed-up of sequential
form in solving 2-person-games of imperfect information is used in GAMBIT [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
      </p>
      <p>
        GAme LAnguage (Gala) [
        <xref ref-type="bibr" rid="ref44">44</xref>
        ] is developed in order to provide an interface to
the game-solving algorithms. Factually, Gala a ords Prolog-based game
descriptions, where a game of extensive form or of normal form can be generated. The
generated game-theoretic representation can be forwarded to GAMBIT or other
game-solving algorithms. The main improvement of Gala compared to these
representations is the game descriptions' compactness as perceived at least at the
      </p>
      <p>
        Approach Crit. Means Class of games
Citation Used
congestion games 1,4 functions subset of n-person games,
[
        <xref ref-type="bibr" rid="ref40">40</xref>
        ] A,C simultaneous moves
sequential form 1,4 matrices 2-person games of
[
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] A,C imperfect information
graph games 1,4 graphs, n-person games,
[
        <xref ref-type="bibr" rid="ref41">41</xref>
        ] A,C functions simultaneous moves
local e ect games 1,4 functions subset of n-person games,
[
        <xref ref-type="bibr" rid="ref42">42</xref>
        ] A,C simultaneous moves
action graph games 1,4 graphs, n-person games,
[
        <xref ref-type="bibr" rid="ref43">43</xref>
        ] A,C functions simultaneous moves
Gala 2 logic n-person games of
[
        <xref ref-type="bibr" rid="ref44">44</xref>
        ] A imperfect information
MAID 1,4 Bayes-nets n-person games of
[
        <xref ref-type="bibr" rid="ref45">45</xref>
        ] A,B imperfect information
continuous games 6 functions subset of 2-person games of
[
        <xref ref-type="bibr" rid="ref46">46</xref>
        ] A imperfect information
timed games 6 functions 2-person games
[
        <xref ref-type="bibr" rid="ref47 ref48">47,48</xref>
        ] B
GDL 1,2,4 logic deterministic n-person games,
[
        <xref ref-type="bibr" rid="ref38">38</xref>
        ] B,C simultaneous moves
GDL-II 1,2,4,5 logic n-person games of
[
        <xref ref-type="bibr" rid="ref49">49</xref>
        ] B,C imperfect information
game Petri-nets 1 Petri-nets deterministic n-person games,
[
        <xref ref-type="bibr" rid="ref50">50</xref>
        ] A simultaneous moves
PNSI 2,4{6 Petri-nets n-person games of
[
        <xref ref-type="bibr" rid="ref51">51</xref>
        ] A{C imperfect information
SIDL2.0 2,5,6 logic n-person games of
[1, p.98] C imperfect information
z-Tree-language 2,3,5,6 imperative n-person games of
[
        <xref ref-type="bibr" rid="ref36">36</xref>
        ] C,D language imperfect information
examples from Gala's software package. Due to full-scale Prolog, Gala does not
provide decidability. Therefore, the generation of extensive form games from
Gala game descriptions must not terminate.
      </p>
      <p>
        There is a subset of game-playing algorithms, which is not only aimed to play
games, but also to simulate human (strategic) reasoning in them. Simulating
human reasoning falls in the subject of cognitive science. There are currently two
di erent approaches, where the human strategic reasoning has to be expressed in
a general language in order to facilitate an e cient comparability of the models.
The rst is based on cognitive architectures [
        <xref ref-type="bibr" rid="ref53">53</xref>
        ][
        <xref ref-type="bibr" rid="ref54">54</xref>
        ], which are languages for
models of general human reasoning. The second is based on Multi-Agent In uence
Diagrams (MAID) [
        <xref ref-type="bibr" rid="ref45">45</xref>
        ]. The second factually conforms the game-theoretic point
of view on strategic interactions and provides the alternative language MAID
for describing games. MAID are shown to be expressive enough to represent
n-person games of imperfect information in the algorithms for game playing.
MAID can be also transformed to extensive form in order to solve them [
        <xref ref-type="bibr" rid="ref55">55</xref>
        ].
      </p>
      <p>
        The previously discussed literature does not mention the inclusion of time
dependent details in game descriptions, what some theoretical approaches from
game theory, concurrency theory [
        <xref ref-type="bibr" rid="ref56">56</xref>
        ] and control engineering [
        <xref ref-type="bibr" rid="ref48">48</xref>
        ] aim. A current
work [
        <xref ref-type="bibr" rid="ref46">46</xref>
        ] in game theory extends extensive form games of perfect information
and continuous time [
        <xref ref-type="bibr" rid="ref57">57</xref>
        ] to such of imperfect information { continuous games.
In [
        <xref ref-type="bibr" rid="ref57">57</xref>
        ][
        <xref ref-type="bibr" rid="ref46">46</xref>
        ], only a subset of such games is regarded { the set of player's actions
is always the same. Generally, a point of time is assigned to every action and
time grows strictly over a sequence of actions.
      </p>
      <p>
        Game Description Language (GDL) succeeded in sparking an international
programing competition on general game playing [
        <xref ref-type="bibr" rid="ref38">38</xref>
        ]. A concrete game
description in GDL is sent to an arti cial game player and never to its human
programmer { the programmer knows only the structure of GDL. This satis es the
criterion 2. For the criterion 5, generality of IGDL's precursors is a trend { either
it will be possible to describe n-person games of imperfect information in IGDL
or IGDL should be extended to facilitate that. This trend caused the
development of GDL-II [
        <xref ref-type="bibr" rid="ref49">49</xref>
        ], which is an extension of GDL for n-person games of
imperfect information. Like GDL, GDL-II is based on Datalog, which is a version of
Prolog [
        <xref ref-type="bibr" rid="ref58">58</xref>
        ]. Datalog guarantees decidability by banning functions, limiting
variables' ranges and restricting recursion. Due to the decidability, the existing game
management algorithm based on GDL-II is guaranteed to terminate. However,
the ban of functions worsen compactness. For instance, if arithmetic addition is
needed to describe actions' consequences in a game, the result for every required
summands' combination must be separately de ned in the game description.
      </p>
      <p>
        There are no time dependent details included explicitly in GDL-II game
descriptions. GDL and GDL-II describe games in a way STRIPS-like [
        <xref ref-type="bibr" rid="ref59">59</xref>
        ] languages
do. In languages for planning tasks, STRIPS-like descriptions can be replaced by
descriptions based on Petri nets [
        <xref ref-type="bibr" rid="ref60">60</xref>
        ]. Petri Nets for Strategic Interaction (PNSI)
is a game description language, which is proposed chronologically between GDL
and GDL-II [
        <xref ref-type="bibr" rid="ref37">37</xref>
        ]. PNSI uses basic Petri nets instead of logic. Petri nets are also
known being used in game theory to describe subclasses of games [
        <xref ref-type="bibr" rid="ref50">50</xref>
        ]. PNSI
provides decidability [1, p.89]. The advantages of PNSI compared with GDL-II
are the graphical representation of Petri nets and the ability to describe games of
equidistant time. Equidistant time means that the game management algorithm
for PNSI pauses exactly for one chronon between two game states [
        <xref ref-type="bibr" rid="ref51">51</xref>
        ], where
a game state is also a node of its game tree. In this context, a chronon is a
constant period of time, which is explicitly known to players. During a chronon,
players' actions can be submitted. The game management algorithm for GDL-II
is not of equidistant time, because the next state is calculated exactly after the
submission of the last action, if it is inside the allowed time period. The time
point of the last submission may vary depending on players. Of cause, GDL-II
is supposed be also able to describe games of equidistant time, if its game
management algorithm is modi ed as proposed for PNSI.
      </p>
      <p>
        For PNSI, there exist an algorithm that can generate games of extensive form
from game descriptions as in the case of Gala [
        <xref ref-type="bibr" rid="ref51">51</xref>
        ]. Therefore, PNSI provides an
interface to game solving algorithms. A game of extensive form generated based
on a PNSI game description is a slightly modi ed state transition system of the
underlying basic Petri net. In this context, a state transition system is an
oriented graph consisting of game states, where every edge represents a progression
in time. There is still no algorithm for GDL-II to generate games of extensive
form. A state transition system can be also generated for GDL-II game
descriptions [
        <xref ref-type="bibr" rid="ref49">49</xref>
        ]. Therefore, generation of extensive form games is supposed to be also
possible for GDL-II game description.
      </p>
      <p>
        PNSI su ers of insu cient compactness as well as GDL-II but in a di
erent way. The arithmetic addition and subtraction are banned in Datalog, but
inherently supported by basic Petri nets. On the other hand, basic Petri nets
require every state to be decoded as a vector of natural numbers and do not have
other operations than the addition and the subtraction. The game description
of the parlor game Nim needs in PNSI much less space than in GDL-II [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ]. The
opposite for chess, a GDL-II chess description needs less.
      </p>
      <p>Dropping the criterion of decidability may dramatically improve
compactness. Strategic Interaction De nition Language (SIDL) is based on ISO-Prolog,
does not provide decidability and attains for example games a higher
compactness [1, p.98]. Of cause, the widely used game description in an imperative
language can be also mentioned. However, the game management part of software
aka game server is then required to send its own code in order to provide explicit
rules [1, p.54].</p>
      <p>
        For scienti c human users beyond computer science, there is an ongoing
development of user-friendly software for experiments [
        <xref ref-type="bibr" rid="ref61">61</xref>
        ]. RatImage [
        <xref ref-type="bibr" rid="ref62">62</xref>
        ] and
TEEC [
        <xref ref-type="bibr" rid="ref61">61</xref>
        ] are examples of the rst generation of such software. They are
libraries, which facilitate programming. The second generation provides already
domain-speci c languages for the game management and the layout of
humancomputer interfaces. These are ComLabGames [
        <xref ref-type="bibr" rid="ref63">63</xref>
        ] and z-Tree [
        <xref ref-type="bibr" rid="ref36">36</xref>
        ]. z-Tree is
the most used [
        <xref ref-type="bibr" rid="ref39">39</xref>
        ]. There is a z-Tree-language, which is actually an imperative
language, in which the game and also the human-computer interfaces can be
described. This language does not provide decidability. It has no relations to game
solving or playing algorithms.
4
      </p>
    </sec>
    <sec id="sec-5">
      <title>Conclusion</title>
      <p>A large-scale view on the problem of understanding human strategic reasoning
is presented. The elaborated solution is the development of the interdisciplinary
research infrastructure. This research infrastructure is proposed to make the
interdisciplinary research more e cient, as it is already observed in similar
interdisciplinary problems. As an underline of the large-scale view, there are matters
chained from di erent sources, which have been never cited together before. For
instance, GDL-II and z-Tree are such matters.</p>
      <p>The elaborated concept is the domain-speci c language IGDL. A summary
of its precursors shows that none of these is developed enough to satisfy IGDL's
full outline. There is still no language, which incorporates the graphical
representation like PNSI, compactness improvements like GDL-II and a proven human
usability like z-Tree-language.</p>
    </sec>
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