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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>A Case Study Exploring Suitability of Bottom Up Modelling and Actor-based Simulation for Decision Making</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>India vinay.vkulkarni@tcs.com</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Asha Rajbhoj Tata Consultancy Services Research Pune</institution>
          ,
          <country country="IN">India</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Prashant Kumar Tata Consultancy Services Research Pune</institution>
          ,
          <country country="IN">India</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>Souvik Barat Tata Consultancy Services Research Pune</institution>
          ,
          <country country="IN">India</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>Traditionally, the top-down design method and analysis techniques, such as system dynamic model, have been used extensively for understanding complex systems. In top-down approach, a system is specified in terms of global state and the desired analyses are performed using aggregated macro-behaviour that represents the overall system. Essentially, the individual elements and their peculiarities are not differentiated with an assumption that the inherent dynamics of the overall system is precisely known to the system modellers. This paper, in contrast, presents a case wherein the system behaviour emerges from the individual elements and their interactions. The paper further demonstrates the usability of bottom up approach, actor based modelling abstraction, and actor based simulation technique to understand complex systems (with emergent behaviour) using a case study on decision making of a Research and Innovation (R&amp;I) organisation.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1 INTRODUCTION</title>
      <p>
        Two design alternatives, named top-down approach and bottom-up
approach, exist for specifying and analysing complex systems [
        <xref ref-type="bibr" rid="ref1">1</xref>
        ].
In top-down approach, a system is visualised in terms of global
state and the behaviour is represented using aggregated
macrobehaviour of the system elements. For example, the System
Dynamics (SD) model [
        <xref ref-type="bibr" rid="ref2">2</xref>
        ] uses the concepts of stocks, flows and
information to represent system state and system level nonlinearity,
feedback loops and the time delays. The behaviour is described
using differential equations. In principal, these modeling elements
and equations represent generalized form of an overall system that
approximates the peculiarity of individual elements. Conceptually,
the top-down approach considers a reductionist view [
        <xref ref-type="bibr" rid="ref3">3</xref>
        ] to
understand system using the mathematical rigour from operational
research, optimization theory, and sophisticated AI algorithms. The
bottom-up approach, in contrast, considers the micro-behaviour of
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individual elements and their interactions in precise form as oppose
to the overall system behaviour. Conceptually, the bottom-up
approach relies on emergentism [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] as advocated in actor model of
computation [
        <xref ref-type="bibr" rid="ref5 ref6">5, 6</xref>
        ], and agent-based systems [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
      </p>
      <p>
        Traditionally, the top-down approach is popular choice (as compare
to the bottom-up approach) for analysing and understanding the
complex systems in the context of critical business needs such as
decision making activities. Existing modelling and analysis tools
supporting top-down approach are extremely efficient for
describing and simulating the aggregated system behaviour.
However, they are not appropriate for precise understanding of
complex and dynamic system that exhibits emergent behaviour and
deals with large number of socio-technical [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] elements having
adaptive, autonomous and dynamic behaviours.
      </p>
      <p>In this paper, we demonstrate the effectiveness of bottom-up
modelling approach to understand a complex and dynamic system
(with emergent behaviour) using a case study that illustrates
decision making of an industrial Research and Innovation (R&amp;I)
organisation. The goals of R&amp;I organisation is to convert
innovative ideas into business offerings, and make significant
scholastic impacts to the research community (through publications
and patents). In this context, the behaviour of the overall R&amp;I
organisation is not well-defined - rather it emerges from the
activities of the individual researchers. Moreover, the progress of
the organisation largely relies on the effective utilization of the
researchers within the dynamic compositions structure where they
operate (i.e., research project).</p>
      <p>
        We adopt the concept of actor model of computation [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] to
represent constituent elements, such as the research projects and
researchers, of R&amp;I organisation; formulate simulation setting by
allowing these elements to interact with each other (as oppose to
describing overall R&amp;I organisation specification); and use actor
based simulation technique to observe the emergent behaviour. The
what-if scenario playing and exploration of decision alternatives to
achieve organisational goals are accomplished through multiple
simulation runs and comparing their results.
      </p>
      <p>The rest of the paper organised as follows: the section 2 introduces
R&amp;I case study, section 3 illustrates the specification of the key
elements of R&amp;I organisation. The simulation runs to explore the
decision alternatives of two key stakeholders of the R&amp;I
organisation namely R&amp;I head and research project head are
illustrated in section 4. The paper concludes in section 5 by
highlighting our learnings from R&amp;I case study and future
explorations.</p>
    </sec>
    <sec id="sec-2">
      <title>2 CASE STUDY DETAILS</title>
      <p>We consider an industrial Research and Innovation (R&amp;I)
organisation of an IT firm that invites new ideas from its
researchers and makes appropriate attempts to convert promising
ideas into innovative business offerings. The R&amp;I organisation
adopts an organisation structure and relies on a research
development process to realise its goals to transform ideas into
business offerings and make significant scholastic impacts. The
organisation structure and behaviour are described below:
Structure: The structural of R&amp;I organisation is depicted in Fig. 1
using a class diagram. As shown in the figure, the R&amp;I organisation
contains multiple research projects and researchers. A research
project is a unit that is formed with appropriate researchers to
transform a research idea into business offering. A research project
is associated with Research Project Type wherein a research project
type represents specific characteristics of the research project. For
example a research project that focuses an immediate industrial
problem expects quick turn-around time (for converting an idea
into business offering) whereas an idea that has potential to change
the state-of-the-art and/or state-of-the-practice takes longer
duration to reach expected maturity level. Similarly an idea that is
not well-explored in research community expects rigorous research
work, comprehensive validation strategy, and convincing
evidences to establish the success. In this paper, we consider three
research project types namely PT1, PT2 and PT3 for illustration
purpose. PT1 type research project focuses on standard research
requirements (with moderate research activity, moderate
solutioning activity, takes moderate time to complete and has
medium risk), PT2 type of research project focuses on
wellexplored research topic (i.e., less research work, more solutioning,
relatively short-term and comparatively less risk), and PT3 type of
research project deals with long term research on unexplored topic
(i.e., more research work, more solutioning, long term and high
risk).</p>
      <p>A research project comprises multiple researchers. A researcher
contributes research work to the research project based on their
research experiences, skills and educational background. In this
case study, the researchers are classified into 4 grades called Chief
Scientist, Senior Scientist, Scientist and Junior Researcher
(labelled as Developer). A range of work capability (i.e., quantum
of work that a researcher is capable of contributing to a research
project) and range of value weightage of the research work
(effectiveness factor of the contributed work) are associated with
these research grades.</p>
      <p>In this setting, two key stakeholders control the organisation and its
units. The R&amp;I organisation is owned by a unit owner, termed as
R&amp;I Head, and a research project is headed by designated
researcher (known as Research Project Head). All research project
heads reports to R&amp;I head.</p>
      <p>Behaviour: The process for transforming research idea into
business offering starts with a new idea from individual researcher
or a group of researchers. The initiator submits new idea as a
research proposal to the research council (designated researchers)
for evaluation. A research project is formed once the idea is
accepted by the research council. Research project largely follows
process steps as described using a state machine in Fig. 2. A
research project progresses through 7 states namely research
problem formulation/definition (RP Def), literature review (LR),
defining line of attack (LoA), defining solution (Solutioning),
internal technical validation through toy-yet-believable
proof-ofconcept (TYB PoC), solution validation through near real-life
proof-of-concept (N_R_L PoC), and external validation through
customer proof-of-concept (Customer PoC). An idea is transformed
into business offering once the Customer PoC is completed
successfully. The state of a research project advances based on the
research work contributed by researchers, and research is
acknowledge in research community through publications and
patents. For example, a research project moves from LR state to
LoA state when adequate research work is performed to address all
research questions of a research project (through literature
reviews), and the literature review outcomes are validated though
appropriate publications. A research project may move from an
internal state to shelved for future work (Shelved FFW) or shelved
for suitable opportunity in future (Shelved PoC) state if the project
is not progressed for a specific duration. For example, the research
project in LR state may move to Shelved FFW state if the progress
is not substantial for 4 weeks in a row. Essentially, each research
project defines the entry-criteria and exist-criteria for all states in
terms of two factors – the progress on the core activities associated
with a state (e.g., literature review activity for LR state) and
validation of the research work through publications. This case
study uses three publication categories namely journal, conference
and workshops and two sub-categories (for each category) termed
as tier 1 and tier 2 for defining such criteria. In addition to these
succession criteria, the R&amp;I unit defines the rules for moving a
research project into shelved states as shown in Fig. 2.
The progress of a research project largely relies on the research
work contributed by individual researchers. A researcher
contributes work for core activities (such as literature review,
arriving at solution, and validating though PoC) and validation
effort (publication and patent related work) based on the
instructions provided by the research project head. The effective
work contribution of an individual researcher for a research project
is primarily a function over effort spent on specific activity and the
value weightage associated with the grade (and the quality) of a
researcher. Further there is a non-linearity associated with the
contribution from individual researcher towards the project
progress. An individual contribution can be accounted to research
project contribution if the contribution is above some threshold
value. For example, a researcher with a value weightage 0.5 spend
30 minutes in a day for literature review related work (which is
equivalent of 15 minutes effective work) cannot be a contribution
from an individual to a research project. One can say that the
minimum one hour of effective work from an individual in a day
should be considered as effective work to a research project.
The external factors, such as paper acceptance, also influence the
research project progression. For example, state transition of a
research project is a function over number of papers accepted for a
specific category. The acceptance of a paper in a
journal/conference/workshop largely depends on internal factors
(such as the quantum of core work done, effort spent for preparing
a paper, the rank of the researchers who contributed to the paper
and the experience of the involved researchers), and external
factors such as the rank of the conference and inherent randomness
associated with the review process, etc.</p>
      <p>
        In this paper, we models individual elements of R&amp;I organisation,
i.e., different kinds of researchers, research projects and
journal/conference/workshop authority, and their interactions to
define R&amp;I organisation. The specification of R&amp;I organisation is
illustrated in section 3.
We model R&amp;I organisation using an actor based language, named
as ESL [
        <xref ref-type="bibr" rid="ref9">9</xref>
        ], that we have developed by extending the concept of
actor model of computation [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] (as described in [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]) for our
overarching research initiative1. ESL is capable of representing an
organisation using a set of modular, autonomous and reactive actors
wherein an actor may define probabilistic behaviour and interacts
with other actors to support emergentism. In particular, an actor
encapsulates the values that represent actor characteristics, state
information, historical data, and the internal elements; actor
exhibits autonomous, stochastic and temporal behaviour, and
supports an interaction protocols to interact with others.
The R&amp;I organisation specification contains two types of internal
actors namely research project actor and researcher actor. It also
contains an actor to represent conference/workshop/journal
authority as shown in Fig. 3.
      </p>
      <p>A research project actor contains:
a. Characteristic variables: to capture the parameters associated
with state transition rules, such as the quantum of core work
expected for each state (as shown in Fig. 2) and expected
publication counts for all publication categories in a state (as
shown in Fig. 2); and the other factors such as the minimum
quantum of effective work expected from an individual
researchers to consider the work as an effective contribution
to a research project.
b. State variables: to represent research project state (i.e., one of
the 7 states presented in Fig. 2), work progress (i.e., how much
work is completed for core activity, publication and patent
related work) in a state, and output produced in a state (i.e.,
number of papers accepted for different publication
categories).
c. History: traces of the research project, and
d. Internal elements: the number of researchers (having their own
grade and behaviour) allocated to a research project.</p>
      <p>The behaviour of a research project actor specifies the state
transition rules using the events that occur within research project
actor (e.g., an event indicating an actor has completed targeted core
work for a state or achieved specific publication targets) and/or the
outside of research project actor (e.g., a paper is accepted in a
journal/conference/workshop). The behaviour of a research project
largely follows the behaviour described by the state-machine
depicted in Fig. 2 and realizes the interaction protocol depicted in
Fig. 3. The type specific variations of the research project to
represent project types PT1, PT2 and PT3 are realised by
parameterising the characteristic variables.</p>
      <p>A research actor encapsulates the characteristics variables that
capture the grade, experiences, areas of interest, efficiency factors
(value weightage), and the work capabilities (a list tuples
describing the research activities and corresponding work limit) of
a researcher. It also captures the work distribution instruction, i.e.,
the list of research work that a researcher should do in week (a
researcher gets this instruction at the time of allocation to a research
project as Expected Work event). The state variable of a researcher
actor captures work done in week and publication counts for
various publication categories; the history captures the experiences
that include the kinds of work done in the past, their quantum, and
achievements such as publication and patent histories. The
behavioural specification captures inherent dynamism and
uncertainty. The dynamism in work contribution from a researcher
to a research project is implemented by factoring evolving value
weightage of the researchers (value weightage changes as the
researcher gain experiences) and considering an uncertainty in
working hours for an activity (typically it is point value from
range). The nonlinearity in effective contribution to a research
project is implemented by considering effective work (computed
from the quantum of work spent in a week and value weightage of
a researcher, where former value is uncertain and later one is
dynamic) to a research project if the effective work is significant
(i.e., effective work is more than a threshold value). The difference
in characteristics of Chief Scientist, Senior Scientist, Scientist and
Developer are realised by parameterising the characteristic
variables of researcher actor.</p>
      <p>The external entity of this case study, i.e., journal editors,
conference organisers and workshop organisers are visualised as
actor with probabilistic behaviour. The research project actor that
sends a paper to this actor gets an acceptance or rejection
notification after a time delay. The acceptance rate and time delay
are pre-defined in this implementation but one may realise a
complex conference system by implementing the dynamics
associated with the paper acceptance behaviour.</p>
    </sec>
    <sec id="sec-3">
      <title>4 SIMULATION</title>
      <p>A simulation of R&amp;I organisation specification is essentially
execution of multiple research projects that start with RP Def state
with specific number of Chief Scientists, Senior Scientists,
Scientists and Developers. The simulation progresses with time
event that represents a ‘week’ time. Researchers contribute efforts
on various activities (as decided by the research project heads and
the research capability of research actor) using contributed work
event (as shown in Fig. 3) every week tick. Research project
consumes contributed work event and computes effective
contribution. Contributed effort gets wasted if effective work is
below expected quantity. The research project triggers submit
paper event to the journal/conference/workshop authority (the
events are shown in Fig. 3) when expected core work and the
minimum paper submission criteria are satisfied for a type of
publication. The authority notifies the acceptance/rejection after
specified time delay. An accepted paper event updates research
project state and researcher state (and history) appropriately.
An internal state change event of a research project is triggered
once state exit criteria is satisfied. The exit criteria of PT1 research
project are shown on every transition edge in Fig 2. For example,
the transition from LR state to LoA state transition is possible only
when 8 PW (Person Week) efforts is spent on LR activity and 2
Tier1workshop papers and 2 Tier2 workshop papers are accepted.</p>
    </sec>
    <sec id="sec-4">
      <title>4.1 Decision making using simulation</title>
      <p>We illustrate relevant what-if scenarios for two stakeholders
of R&amp;I organisation namely the Research Project Head and R&amp;I
Head. The goals of the research project heads are to reach business
offering state within desired time and make significant scholastic
contributions in terms of papers and patents. The research project
heads explore the decision alternatives associated with researchers
profiles (the capability of the researchers), team distribution
(research profile), the work distribution in terms of core work and
publication related work, etc. In contrast, the R&amp;I Head, who
manages multiple research projects (with different research project
type), explores suitable strategy to maintain a steady flow of
innovative business offerings and improve research portfolio with
high impact publications and patents. In the interest of space, we
discuss limited what-if scenarios in this paper.
4.1.1 Research Project Head
In this sub-section, we first demonstrate a case (scenario 1) of an
R&amp;I organisation with five PT1 research projects each having one
Chief Scientist, two Senior Scientists, four Scientists and four
Developers , and then we explore improvement alternatives.
Initially, we observe the progress of R&amp;I organisation with a setting
defined for scenario 1 by simulating R&amp;I organisation specification
for two years (considering ‘week’ as primitive simulation tick). The
overall observation is depicted in Fig. 4.a (the graph is generated
by averaging 20 simulation runs to show statistically significant
result) and key data points are recorded in Table 1 (for readability
purpose). As shown in the figure and table, one research project
(out of 5) has reached to the final state (i.e., Customer PoC is
completed) whereas one research project has reached to N_R_L
PoC state and one has reached to TYB PoC state respectively. Two
research projects have ended up in Shelved PoC state. The key
reason for slow progression is for not achieving the publication
target as shown in the diagram (in Fig. 4.a). In particular, the
research project has gone to Shelve PoC state for not contributing
sufficient progress on Tier 1 conference paper for more than 4
weeks. It is also observed that the effort spent on patent related
activity is exceeded to an extent for some research projects.
Next we demonstrate a scenario (scenario 2) that explores the
impact on allocating more researchers to the earlier simulation
settings. In this scenario, 1 Chief Scientist, 4 Senior Scientists, 8
Scientists (instead of 4 in earlier setting) and 8 Developers (instead
of 4 in earlier setting) are allocated to PT1 research project and the
progress is observed for five PT1 research projects. The
progression, recorded in Table 1, is not satisfactory. The issue with
tier 1 conference paper is continued in this scenario and significant
wastage on tier 1 conference related work is additionally observed.
The simulation result provides a hint that the resources allocated to
the research project are not capable for tier 1 conference publication
i.e., researchers are putting their effort in tier 1 conference paper
but the effective contribution from individual researchers are not
adequate to reach individual threshold value.</p>
      <p>We further demonstrate two scenarios – scenario 3 and scenario 4.
In scenario 3, 1 Chief Scientist, 2 Senior Scientists, 4 Scientists and
4 Developers are allocated as scenario 1. However, this scenario
considers different work distribution to reduce excessive work on
patent and focus more on Tier 1 conference paper (mainly by Chief
Scientist and Senior Scientist). In this scenario, 2 research projects
have reached to customer PoC, 2 research projects have reached to
N_R_L PoC and 1 research project has reached to TyB PoC. For
further improvement, the allocation of researchers with better
experience is considered (scenario 4). With this setting, 2 research
projects have reached to Customer PoC, 3 research projects have
reached to N_R_L PoC. This scenario playing capability shows
how formation of simulation setting and simulation results lead to
a decision making. In next section, we illustrate the scenario
playing capability of R&amp;I head.
4.1.2 R&amp;I Head
As discussed earlier, R&amp;I head tries to improve the flow of business
offerings (i.e., the ideas that reaches to Customer PoC state) and
maximize the publication portfolio in terms of publications and
patents. We configure an R&amp;I organisation with five PT1 type
research projects, five PT2 type research projects and five PT3 type
research projects. The simulation results describing research
project progresses and publication counts of these three types of
research projects are shown in Fig. 5. As shown in the figure, the
PT2 type research projects are producing more business offerings
than PT3 type research projects and PT3 type research projects are
producing more business offering than PT1 type research projects.
In contrast, PT3 types research project are producing more
publications than PT1 types research projects and PT1 type
research projects are performing better than PT2 for publication.
Thus PT2 type research project is better for churning out business
offerings but not so effective for scholastic impacts whereas PT3
type research projects are better for scholastic impacts but not
affective for producing business offerings.</p>
      <p>R&amp;I head can explore the suitable combination of PT1, PT2 and
PT3 in R&amp;I organisation to optimise the business impact and
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scholastic impact through simulation runs. For example, the R&amp;I
head can explore what will be the situation if PT2 types of research
projects are encouraged within R&amp;I organisation. We evaluate this
scenario by reducing PT1 type of research project to 2 (from 5),
increasing PT2 type of research to 8 (from 5), and keeping PT3 type
research project count unchanged. We observed marginal
improvement in business offering as shown in Table 2 but
significant reduction in publications and patents counts as shown in
Table 3. For an illustration of scenario playing capability, we
simulated another scenario with 4 PT1 type research projects, 2 PT2
type research projects and 9 PT1 type research project. The
simulation result is recorded in Table 2 and Table 3 respectively.
As shown in the tables, the significant improvement is observed in
publication (shown in Table 3) without any trade off on business
offering (as shown in Table 2).
In this paper, we adopted bottom up approach as a design
methodology and exploited actor model [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ] as design abstraction to
specify R&amp;I organisation. Further, we applied simulation technique
to explore decision alternatives of two key stakeholders of R&amp;I
organisation. In particular, we visualised R&amp;I organisation using its
constituent elements; the constituent elements are specified using
the concept of actor; and finally emergent behaviour is observed
through simulation run (i.e., the output produced by ESL simulation
engine). We also demonstrated how probabilistic behaviour (e.g.
paper acceptance), randomness (e.g. effort spent in day),
nonlinearity (e.g., effective research work), and dynamism (e.g.
resources experience) of individual elements (that are represented
as actors) influence the overall system behaviour (e.g. progress of
research project and R&amp;I organisation as a whole) over multiple
simulation runs.
      </p>
      <p>
        From methodology perspective our focus (while specifying R&amp;I
organisation) was to find constituent elements of R&amp;I organisation,
understand their micro-behaviours and interactions (rather than
understanding the overall system behaviour of R&amp;I organisation).
Moreover, the what-if scenario playing are also driven by
individual elements (for example, what will be the situation if a
research project head recruits more eligible researchers in a
research project, or research head instructs team member to work
differently) and emergentism rather the following the principles of
top-down approaches [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ] where the primary exploration objective
is to change high-level system parameters and observe system
performance.
      </p>
      <p>We found the use of bottom up approach is favorable for two key
activities: a) specification: the specification does not expect
additional expertise (other than knowing specification language)
for abstracting out the system behaviour in terms of equations or
any other aggregated form (one should specify elements as one see
them in reality), and b) exploration of decision alternative: the
change specification to explore decision alternatives are localized
within actor (no need to find out a system parameter that represents
the changes). The complete case study (not elaborated in this paper
due to space limitation) makes us believe that the bottom up
approach, actor model and simulation are suitable for
understanding the intricacy of socio technical systems.
However, we acknowledge that the case study is not sufficiently
large to validate our claim. More experiments and real life business
critical case studies are needed. At present, we are working on a
case study with more complexities. For example, we considered the
research projects as fairly independent element and they do not
compete with other research projects for resources (i.e.,
researchers) and research outputs. Moreover, we experimented our
options without any constraints such as financial constraint and
resource limitation. The psychological aspect of the researchers
while working in a research project are also not considered in this
case study. Introducing them in our case study and exploring
tradeoff, competition and optimization (under constraints) are our next
focus.</p>
    </sec>
    <sec id="sec-5">
      <title>ACKNOWLEDGEMENT</title>
      <p>We would like to thank Prof. Tony Clark (Sheffield Hallam
University, UK) for providing necessary support to extend ESL for
completing this case study and Prof. Balbir Barn (Middlesex
University, London) for his guidance on design methodology.</p>
    </sec>
  </body>
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