<!DOCTYPE article PUBLIC "-//NLM//DTD JATS (Z39.96) Journal Archiving and Interchange DTD v1.0 20120330//EN" "JATS-archivearticle1.dtd">
<article xmlns:xlink="http://www.w3.org/1999/xlink">
  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Value of Smart Data for Supply Chain Decisions in a Data Rich, Uncertain World</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Ganesh Sankaran</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>
        <contrib contrib-type="author">
          <string-name>Martin Knahl</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Guido Siestrup</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ismini Vasileiou</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>Decision Making Under Uncertainty in Digital Supply Chains</institution>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Hochschule Furtwangen University</institution>
          ,
          <addr-line>Robert-Gerwig-Platz 1, 78120 Furtwangen</addr-line>
          ,
          <country country="DE">Germany</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>University of Plymouth, Drake Circus</institution>
          ,
          <addr-line>Plymouth, Devon PL4 8AA</addr-line>
          ,
          <country country="UK">United Kingdom</country>
        </aff>
      </contrib-group>
      <fpage>49</fpage>
      <lpage>54</lpage>
      <abstract>
        <p>Data-driven decisions are becoming increasingly relevant for supply chains as traditional paradigms are being replaced with concepts and approaches more suited for the advent of big data. However, the prevailing consensus is that companies are struggling to cope with an overabundance of data, which presents the following pertinent question: how to efficiently analyze data applying filters of relevance and insightfulness to make effective decisions? There is currently a lack of research focus on providing quantitative tools to do such analyses. This paper, besides offering thoughts on decision-making uncertainty in a digital supply chain context, describes an approach to address the research gap. The approach (which involves developing a quantitative model) is further elucidated by utilizing an example in the agricultural supply chain that illustrates how value of data can be quantified by measuring the performance impact of insights delivered using uncertainty reduction as the leverage.</p>
      </abstract>
      <kwd-group>
        <kwd>Supply Chain Management</kwd>
        <kwd>Digital Technologies</kwd>
        <kwd>Big Data Analytics</kwd>
        <kwd>Uncertainty</kwd>
        <kwd>Data Driven Decision Making</kwd>
        <kwd>Value of Data</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>-</title>
      <p>
        opportunity to achieve parity in the OIPT sense (between information processing need
and attendant capacity) and drive improved performance resulting in a higher utilization
of data. However, various studies show that most digital data that is captured is not
utilized [
        <xref ref-type="bibr" rid="ref4">4</xref>
        ] and less than 1% of unstructured data is analyzed at all [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ]. Research in the
areas of digital transformation and Value of Information (VOI) offer up some clues to
clarify this contradiction.
      </p>
      <p>
        Digital transformation is about innovating new business models and ways of value
creation and capture, focusing on the dual outcomes of customer engagement and
integrated digitized solutions. It is perhaps better understood by contrasting with a related
term – digitization, which on the other hand, is a narrower technology-centric view [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ].
Not surprisingly, supply chains that focus on transformation perform significantly
better than peers [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. On the other hand, a lack of transformation focus leads to unmet
expectations and such companies are apt to complain, as have six out of 10 respondents
in this survey of 3000 executives, of having more data than they can use effectively [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ].
      </p>
      <p>
        A related line of research inquiry concerns VOI in a big data context. Research into
Information Systems (IS) following IS economics tradition highlight the lack of tools
to quantify data and the need to address the challenge of “finding a way to quantify the
value of information that considers both insightfulness and risks” [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ]. The two lines of
inquiry are linked, and the convergence is in the fact that supply chains that are
transformation focused are more likely to want to justify investments and therefore also want
to quantify value of data - and this is where this research aims to contribute.
      </p>
      <p>Approaches for Measuring Business Value of Data</p>
    </sec>
    <sec id="sec-2">
      <title>State-of-the-Art</title>
      <p>
        Using a resource-based view, which holds that heterogeneity of organizational
resources is a source of value (as it differentiates a firm from competition), Melville et al.
[
        <xref ref-type="bibr" rid="ref9">9</xref>
        ] argue for consideration of competition and environmental factors to measure value
of data as they are seen to impact value. Higher the level of competition or industry
concentration, higher is the marginal product and, conversely, lack of competition
creates slack resources leading to lower productivity [
        <xref ref-type="bibr" rid="ref10">10</xref>
        ]. Environmental factors or
external focus, on the other hand, is seen to enhance performance as timely and accurate
information regarding a firm’s external environment are preconditions for agility [
        <xref ref-type="bibr" rid="ref11">11</xref>
        ].
      </p>
      <p>
        Besides several empirical studies that adopt a general view on the impact of data on
value and emphasize the link between data-driven decision making and firm output and
productivity (see [
        <xref ref-type="bibr" rid="ref12 ref13">12, 13</xref>
        ] for representative examples), there are also several studies on
particular problem instances. Ketzenberg et al. [
        <xref ref-type="bibr" rid="ref14">14</xref>
        ] assessed VOI in the presence of
uncertainty around demand, return, and product recovery delivering a key insight that
greater the uncertainty, greater is the VOI. Dunke and Nickel [
        <xref ref-type="bibr" rid="ref15">15</xref>
        ] incorporated
forward-looking information in supply chain planning and proposed an optimization
model that utilizes preview of future information with help of lookahead devices (e.g.
sensors) to transform an uncertain future into a certain one.
2.2
      </p>
    </sec>
    <sec id="sec-3">
      <title>Need for Further Research</title>
      <p>
        The discussion above points to a wealth of empirical studies and models for specific
problems. However, a general-purpose quantitative model with a normative character
(elaborated in 2.3) is lacking. In a review of 117 articles on the topic of research
contributions in this area, Viet et al. [
        <xref ref-type="bibr" rid="ref16">16</xref>
        ] had found that, in a supply chain decisions’
context, there is disproportionate attention being paid to inventory whilst other areas have
received insufficient attention. They also report that the impact of new and innovative
data sources (e.g. sensor data) remains under-explored. In laying out a research agenda
for future information systems research, Abbasi et al. [
        <xref ref-type="bibr" rid="ref8">8</xref>
        ] call for research on the “value
of various data sources and channels in terms of quality of insights, enabling new
capabilities, and quantifiable business value.”
2.3
      </p>
    </sec>
    <sec id="sec-4">
      <title>Model Conceptualization</title>
      <p>
        Before describing the proposed model, it is instructive to go over key model attributes
that were considered as prerequisites: (1) Quantitative: the overarching question calls
for the ability to measure the incremental value of insights from digital data. This
necessitates a quantitative-based model that yields a numerical solution. (2) Predictive:
The model must emulate a decision-making process where the performance potential
of data-driven insights can be studied. This requires the model to embody predictive or
simulative capability. (3) Relevant: Zadeh’s principle of incompatibility holds that
complexity makes relevance and precision impossible to obtain simultaneously [
        <xref ref-type="bibr" rid="ref17">17</xref>
        ].
Therefore, the model needs to be built on a framework that lends itself to strike the right
balance. From a performance measurement perspective, it needs to be inclusive (one of
the key characteristics of a good performance measurement framework [
        <xref ref-type="bibr" rid="ref18">18</xref>
        ]) and not
predisposed to any specific supply chain strategy. For instance, both cost (primary
focus for efficient supply chains) and agility (primary focus for responsive supply chains)
measures need to be supported. (4) Usable: as the key question being addressed most
interests supply chain managers, the model should, despite its quantitative rigor, include
a graphical component for the decision-making process to be analyzed visually as well.
      </p>
      <p>
        The proposed model is grounded in the Approximate Dynamic Programming (ADP)
methodology [
        <xref ref-type="bibr" rid="ref19">19</xref>
        ] (also called reinforcement learning). It is an active field of research
that has a long history owing to its evolution from work done in optimal control theory
and stochastic approximation (dynamic programming and Markov decision processes).
ADP’s choice as the model’s underpinning is due to its suitability vis-à-vis
prerequisites set forth earlier and its effectiveness in addressing the class of problems typical of
the supply chain problem domain. One way to justify this claim is by noting the
subcomponents of ADP and highlighting structural similarities between ADP and Supply
Chain (SC) problems. ADP problem formulation consists of policy, reward, value and
model environment. The solution involves an appropriate choice of policy, which is a
set of endogenous controllable variables (e.g. reorder point in SC) in the face of
uncertainty expressed by the model environment (exogenous information, for e.g., customer
demand in SC) to maximize cumulative rewards or value (e.g. global perspective in
SC). The approximate nature of ADP allows problems involving large state-spaces
(typical of SC) to be solved by using an approximation architecture. The approximation
architecture or the learning element allows better policies to be adopted as the system
learns to interpret the uncertain environment better and develops a more accurate
picture of the (delayed) consequence of actions on value. For the proposed model, this last
aspect is crucial to modelling the recalibration of uncertainty due to infusion of digital
data. [
        <xref ref-type="bibr" rid="ref20">20</xref>
        ]
      </p>
      <p>
        The model incorporates formalisms to represent key elements of uncertainty and
digital data. For this research, uncertainty is viewed as an empirical quantity [
        <xref ref-type="bibr" rid="ref21">21</xref>
        ] that
can be modelled as a probability distribution. Furthermore, a Bayesian view of
probability is adopted (other view being frequentist) [
        <xref ref-type="bibr" rid="ref21">21</xref>
        ], which is suitable in this
problemcontext of decision-making where beliefs about states of the world are conditioned on
all available information. Quantification of uncertainty is a relatively untapped aspect
in stochastic optimization literature [
        <xref ref-type="bibr" rid="ref22">22</xref>
        ] but will be an essential component in the
model as it impacts policy selection and consequently its predictive ability. In the case
of digital data, a semantic model (for example, based on W3C SSN ontology [
        <xref ref-type="bibr" rid="ref23">23</xref>
        ]) is
adopted that provides similar modelling rigor. Finally, for model visualization, System
Dynamics (SD) approach is the primary candidate [
        <xref ref-type="bibr" rid="ref24">24</xref>
        ]. SD provides an intuitive
representation of causal relationships between variables and their impact on performance.
2.4
      </p>
    </sec>
    <sec id="sec-5">
      <title>Illustration of Model Aspects: Example in the Agricultural Supply Chain</title>
      <p>The example pertains to the production and sales of seeds that starts with the production
stage (that involves sowing, growing, harvesting, treatment and packaging) and
culminates in the sales of seeds to farmers. The problem of estimating yield is the focus of
the example and it helps elicit the salient model features.</p>
      <p>Once sales projections are made, production is planned assuming a certain yield
(using factors like crop physiology). However, this is at best a noisy or imprecise estimate
and the reality at harvest time tends to vary widely from projections. One key
implication is the planning of treatment and packaging capacity, which is often a bottleneck. If
the capacity planned is insufficient, it leads to lost sales and higher than required
capacity leads to poor utilization and impinges on profits. However, advances in digital
technologies provide the ability to use sensors and the like, which act as lookahead
mechanisms and can provide advance insights during the lengthy sow-grow-harvest
cycle, which can help revise noisy prior estimates with updated, sharper posterior
estimates. The dynamics of interaction are presented in Fig. 1. As can be seen from the
illustration, relevant sensor data (e.g. weather, water content) that are predictors of yield
when captured can be utilized to revise estimates and perform contingency planning in
the form of organizing additional subcontracting capacity or shaping demand
(promotions) to better match demand and supply. In this way, the proposed model emulates
decision making with and without insights from digital data to evaluate the impact on
metrics (e.g. backorders, capacity utilization). The key objective is to make the model
suitable for assessing investments (for instance by facilitating small-scale experiments)
by focusing on the potential for better decision making under uncertainty whereby
return on investment can be calculated as a function of incremental value due to insights.
An implication of wide adoption of digital technologies by supply chains is the increase
in decision-making complexity and uncertainty, which translates to a greater burden on
information processing needs and capabilities. This strain is apparent in various studies
that show that digital data is heavily under-utilized.</p>
      <p>This paper proposed a quantitative-based model that assesses data in terms of its
insightfulness, thereby enabling supply chains to address the problem of
under-utilization and seeks to provide a means to evaluating digital data based on its moderating
influence on uncertainty and its impact on process performance metrics.</p>
      <p>The focus of the next stage of research is resolving design decisions pertaining to
model conceptualization, which is followed by model development. The third and final
stage will be model solving that is supplemented with a case-oriented proof-of-concept.</p>
    </sec>
  </body>
  <back>
    <ref-list>
      <ref id="ref1">
        <mixed-citation>
          1.
          <string-name>
            <surname>Silver</surname>
            <given-names>EA</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Pyke</surname>
            <given-names>DF</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Peterson</surname>
            <given-names>R</given-names>
          </string-name>
          (
          <year>1998</year>
          )
          <article-title>Inventory management and production planning and scheduling, 3</article-title>
          . ed. Wiley, New York, NY
        </mixed-citation>
      </ref>
      <ref id="ref2">
        <mixed-citation>
          2.
          <string-name>
            <surname>Simon</surname>
            <given-names>HA</given-names>
          </string-name>
          (
          <year>1977</year>
          )
          <article-title>The new science of management decision, Rev</article-title>
          . ed. Prentice-Hall,
          <string-name>
            <given-names>Englewood</given-names>
            <surname>Cliffs</surname>
          </string-name>
          ,
          <string-name>
            <surname>N.J.</surname>
          </string-name>
        </mixed-citation>
      </ref>
      <ref id="ref3">
        <mixed-citation>
          3.
          <string-name>
            <surname>Galbraith</surname>
            <given-names>JR</given-names>
          </string-name>
          (
          <year>1974</year>
          )
          <article-title>Organization Design: An Information Processing View</article-title>
          .
          <source>Interfaces</source>
          <volume>4</volume>
          (
          <issue>3</issue>
          ):
          <fpage>28</fpage>
          -
          <lpage>36</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref4">
        <mixed-citation>
          4.
          <string-name>
            <surname>Manyika</surname>
            <given-names>J</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Chui</surname>
            <given-names>M</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Bisson</surname>
            <given-names>P</given-names>
          </string-name>
          et al. (
          <year>2015</year>
          )
          <article-title>Unlocking the potential of the Internet of Things</article-title>
          . https://www.mckinsey.
          <article-title>com/business-functions/digital-mckinsey/our-insights/the-internetof-things-the-value-of-digitizing-the-physical-world</article-title>
          .
          <source>Accessed 21 Jan 2019</source>
        </mixed-citation>
      </ref>
      <ref id="ref5">
        <mixed-citation>
          5.
          <string-name>
            <surname>DalleMule</surname>
            <given-names>L</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Davenport</surname>
            <given-names>TH</given-names>
          </string-name>
          (
          <year>2017</year>
          )
          <article-title>What's Your Data Strategy? https://hbr</article-title>
          .org/
          <year>2017</year>
          /05/whats-your
          <article-title>-data-strategy</article-title>
          .
          <source>Accessed 12 November 2018</source>
        </mixed-citation>
      </ref>
      <ref id="ref6">
        <mixed-citation>
          6.
          <string-name>
            <surname>Ross</surname>
            <given-names>JW</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Sebastian</surname>
            <given-names>IM</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Beath</surname>
            <given-names>CM</given-names>
          </string-name>
          et al. (
          <year>2017</year>
          )
          <article-title>Designing Digital Organizations - Summary of Survey Findings</article-title>
          . https://media-publications.bcg.com/MIT-CISR-
          <article-title>Designing-DigitalSurvey</article-title>
          .
          <source>PDF. Accessed 12 Nov 2018</source>
        </mixed-citation>
      </ref>
      <ref id="ref7">
        <mixed-citation>
          7.
          <string-name>
            <surname>LaValle</surname>
            <given-names>S</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Lesser</surname>
            <given-names>E</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Shockley</surname>
            <given-names>R</given-names>
          </string-name>
          et al. (
          <year>2011</year>
          )
          <article-title>Big Data, Analytics and the Path From Insights to Value</article-title>
          . https://sloanreview.mit.edu/article/big
          <article-title>-data-analytics-and-the-path-from-insightsto-value/</article-title>
          .
          <source>Accessed 28 Jun 2018</source>
        </mixed-citation>
      </ref>
      <ref id="ref8">
        <mixed-citation>
          8.
          <string-name>
            <surname>Abbasi</surname>
            <given-names>A</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Sarker</surname>
            <given-names>S</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Chiang</surname>
            <given-names>RHL</given-names>
          </string-name>
          (
          <year>2016</year>
          )
          <article-title>Big Data Research in Information Systems: Toward an Inclusive Research Agenda</article-title>
          .
          <source>Journal of the Association for Information Systems</source>
          <volume>17</volume>
          (
          <issue>2</issue>
          )
        </mixed-citation>
      </ref>
      <ref id="ref9">
        <mixed-citation>
          9.
          <string-name>
            <surname>Melville</surname>
          </string-name>
          , Kraemer, Gurbaxani (
          <year>2004</year>
          )
          <article-title>Review: Information Technology and Organizational Performance: An Integrative Model of IT Business Value</article-title>
          .
          <source>MIS Quarterly</source>
          <volume>28</volume>
          (
          <issue>2</issue>
          ):
          <fpage>283</fpage>
        </mixed-citation>
      </ref>
      <ref id="ref10">
        <mixed-citation>
          10.
          <string-name>
            <surname>Melville</surname>
            <given-names>N</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Gurbaxani</surname>
            <given-names>V</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Kraemer</surname>
            <given-names>K</given-names>
          </string-name>
          (
          <year>2007</year>
          )
          <article-title>The productivity impact of information technology across competitive regimes: The role of industry concentration and dynamism</article-title>
          .
          <source>Decision Support Systems</source>
          <volume>43</volume>
          :
          <fpage>229</fpage>
          -
          <lpage>242</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref11">
        <mixed-citation>
          11.
          <string-name>
            <surname>Tambe</surname>
            <given-names>P</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Hitt</surname>
            <given-names>LM</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Brynjolfsson</surname>
            <given-names>E</given-names>
          </string-name>
          (
          <year>2012</year>
          )
          <article-title>The Extroverted Firm: How External Information Practices Affect Innovation and Productivity</article-title>
          .
          <source>Management Science</source>
          <volume>58</volume>
          :
          <fpage>843</fpage>
          -
          <lpage>859</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref12">
        <mixed-citation>
          12.
          <string-name>
            <surname>Brynjolfsson</surname>
            <given-names>E</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Hitt</surname>
            <given-names>LM</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Kim</surname>
            <given-names>HH</given-names>
          </string-name>
          (
          <year>2011</year>
          )
          <article-title>Strength in Numbers: How Does Data-Driven Decisionmaking Affect Firm Performance?</article-title>
          SSRN Journal
        </mixed-citation>
      </ref>
      <ref id="ref13">
        <mixed-citation>
          13.
          <string-name>
            <surname>Yu</surname>
            <given-names>W</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Chavez</surname>
            <given-names>R</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Jacobs</surname>
            <given-names>MA</given-names>
          </string-name>
          et al. (
          <year>2018</year>
          )
          <article-title>Data-driven supply chain capabilities and performance: A resource-based view</article-title>
          .
          <source>Transportation Research Part E: Logistics and Transportation Review</source>
          <volume>114</volume>
          :
          <fpage>371</fpage>
          -
          <lpage>385</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref14">
        <mixed-citation>
          14.
          <string-name>
            <surname>Ketzenberg</surname>
            <given-names>ME</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Laan</surname>
            <given-names>E</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Teunter</surname>
            <given-names>RH</given-names>
          </string-name>
          (
          <year>2006</year>
          )
          <article-title>Value of Information in Closed Loop Supply Chains</article-title>
          .
          <source>Production and Operations Management</source>
          <volume>15</volume>
          :
          <fpage>393</fpage>
          -
          <lpage>406</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref15">
        <mixed-citation>
          15.
          <string-name>
            <surname>Dunke</surname>
            <given-names>F</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Heckmann</surname>
            <given-names>I</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Nickel</surname>
            <given-names>S</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Saldanha-</surname>
          </string-name>
          da
          <string-name>
            <surname>-Gama</surname>
            <given-names>F</given-names>
          </string-name>
          (
          <year>2018</year>
          )
          <article-title>Time traps in supply chains: Is optimal still good enough?</article-title>
          <source>European Journal of Operational Research</source>
          <volume>264</volume>
          :
          <fpage>813</fpage>
          -
          <lpage>829</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref16">
        <mixed-citation>
          16.
          <string-name>
            <surname>Viet</surname>
            <given-names>NQ</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Behdani</surname>
            <given-names>B</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Bloemhof</surname>
            <given-names>J</given-names>
          </string-name>
          (
          <year>2018</year>
          )
          <article-title>The value of information in supply chain decisions: A review of the literature and research agenda</article-title>
          .
          <source>Computers &amp; Industrial Engineering</source>
          <volume>120</volume>
          :
          <fpage>68</fpage>
          -
          <lpage>82</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref17">
        <mixed-citation>
          17.
          <string-name>
            <surname>Lovell</surname>
            <given-names>B</given-names>
          </string-name>
          (
          <year>1995</year>
          )
          <article-title>A Taxonomy of Types of Uncertainty</article-title>
          . Dissertations and Theses
        </mixed-citation>
      </ref>
      <ref id="ref18">
        <mixed-citation>
          18.
          <string-name>
            <surname>Beamon</surname>
            <given-names>BM</given-names>
          </string-name>
          (
          <year>1999</year>
          )
          <article-title>Measuring supply chain performance</article-title>
          .
          <source>Int Jrnl of Op &amp; Prod Mnagemnt</source>
          <volume>19</volume>
          (
          <issue>3</issue>
          ):
          <fpage>275</fpage>
          -
          <lpage>292</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref19">
        <mixed-citation>
          19.
          <string-name>
            <surname>Powell</surname>
            <given-names>WB</given-names>
          </string-name>
          (
          <year>2014</year>
          )
          <article-title>Clearing the Jungle of Stochastic Optimization</article-title>
          . In:
          <string-name>
            <surname>Newman</surname>
            <given-names>AM</given-names>
          </string-name>
          , Leung J (eds)
          <article-title>Tutorials in operations research: Bridging data and decisions</article-title>
          . INFORMS, Hanover, Md, pp
          <fpage>109</fpage>
          -
          <lpage>137</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref20">
        <mixed-citation>
          20.
          <string-name>
            <surname>Sutton</surname>
            <given-names>RS</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Barto</surname>
            <given-names>AG</given-names>
          </string-name>
          (
          <year>1998</year>
          )
          <article-title>Reinforcement learning: An introduction / Richard S. Sutton</article-title>
          and
          <string-name>
            <given-names>Andrew G.</given-names>
            <surname>Barto</surname>
          </string-name>
          .
          <article-title>Adaptive computation and machine learning</article-title>
          . MIT Press, Cambridge, Mass., London
        </mixed-citation>
      </ref>
      <ref id="ref21">
        <mixed-citation>
          21.
          <string-name>
            <surname>Morgan</surname>
            <given-names>MG</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Henrion</surname>
            <given-names>M</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Small MJ</surname>
          </string-name>
          (
          <year>1990</year>
          )
          <article-title>Uncertainty: A guide to dealing with uncertainty in quantitative risk and policy analysis / M. Granger Morgan and Max Henrion with a chapter by Mitchell Small</article-title>
        </mixed-citation>
      </ref>
      <ref id="ref22">
        <mixed-citation>
          22.
          <string-name>
            <surname>Powell</surname>
            <given-names>WB</given-names>
          </string-name>
          (
          <year>2017</year>
          )
          <article-title>A Unified Framework for Stochastic Optimization</article-title>
          . https://castlelab.princeton.edu/wp-content/uploads/2017/09/Powell-UnifiedFrameworkStochasticOptimization_
          <article-title>July222017</article-title>
          .pdf.
          <source>Accessed 30 Jan 2019</source>
        </mixed-citation>
      </ref>
      <ref id="ref23">
        <mixed-citation>
          23.
          <string-name>
            <surname>Ganzha</surname>
            <given-names>M</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Paprzycki</surname>
            <given-names>M</given-names>
          </string-name>
          ,
          <string-name>
            <surname>Pawlowski</surname>
            <given-names>W</given-names>
          </string-name>
          et al. (
          <year>2017</year>
          )
          <article-title>Streaming semantic translations</article-title>
          .
          <source>In: 2017 21st International Conference on System Theory, Control and Computing (ICSTCC): Proceeeings : October 19 - 21</source>
          ,
          <year>2017</year>
          , Sinaia, Romania. IEEE, [Piscataway, New Jersey], pp
          <fpage>1</fpage>
          -
          <lpage>8</lpage>
        </mixed-citation>
      </ref>
      <ref id="ref24">
        <mixed-citation>
          24.
          <string-name>
            <surname>Duggan</surname>
            <given-names>J</given-names>
          </string-name>
          (
          <year>2006</year>
          )
          <article-title>A Comparison of Petri Net and System Dynamics Approaches for Modelling Dynamic Feedback Systems</article-title>
        </mixed-citation>
      </ref>
    </ref-list>
  </back>
</article>