=Paper= {{Paper |id=Vol-2749/paper3 |storemode=property |title=Organizational Modeling for Blockchain Oriented Software Engineering with Extended-i* and UML |pdfUrl=https://ceur-ws.org/Vol-2749/paper3.pdf |volume=Vol-2749 |authors=Anne Sofie Vingerhouts,Samedi Heng,Yves Wautelet |dblpUrl=https://dblp.org/rec/conf/ifip8-1/VingerhoutsHW20 }} ==Organizational Modeling for Blockchain Oriented Software Engineering with Extended-i* and UML== https://ceur-ws.org/Vol-2749/paper3.pdf
      Organizational Modeling for Blockchain Oriented
      Software Engineering with Extended-i* and UML

           Anne Sofie Vingerhouts1 , Samedi Heng2 , and Yves Wautelet1
                              1
                                 KU Leuven, Leuven, Belgium
                            yves.wautelet@kuleuven.be,
                       2
                         HEC Liège, Université de Liège, Liège, Belgium
                               samedi.heng@uliege.be



        Abstract. No standard modeling technique exists for Requirements Engineering
        (RE) and Organizational Modeling (OM) within Blockchain-Oriented Software
        Engineering. This paper aims to provide preliminary advices through the study of
        two modeling frameworks when representing blockchain-supported processes in
        Supply Chain (SC) Management (SCM), namely the i* framework and the Uni-
        fied Modeling Language (UML) Use Case and Sequence Diagrams. This paper
        illustrates findings on a real life case study called ‘Farm-to-Fork’. The case study
        provides a blockchain solution for the SC of farm animals. The modeling tech-
        niques are applied to uncover their pros and cons in this context. The paper points
        to the use of (extended) i* representations and the aforementioned UML diagrams
        in a complementary way because of the various perspectives they provide to de-
        velop a blockchain: while i* fits during early RE/OM phases to understand the
        ‘why’ of the SC processes, UML better fits the late RE/OM and design stages by
        offering concrete diagrams to understand the ‘what’ and ‘how’.


Keywords: i* framework, Blockchain, Blockchain-Oriented Software Engineering, Con-
ceptual Modeling, Supply Chain Management, Distributed Ledger.


1    Introduction and Related Work
Since Bitcoin’s boom in 2018, the use of the underlying Blockchain Technology (BT)
to store transactional data has driven a lot of interest. Application of BT can notably
be found in SCM. Major characteristics of BT like immutability, transparency, trace-
ability, high transactional speed, security and cost-effectiveness are indeed well aligned
with SCs key objectives [10]. There is no commonly agreed modeling standard for BT
adoption [15] so that this paper studies what modeling language could be used for such
a purpose with a specific focus on the SC domain. Two of them, i* [28] (which has
proven its relevance for complex organizational modeling) and UML’s Use Case and
Sequence Diagram [13] (largely adopted in the industry) are applied and evaluated.
     The i* framework is a goal-oriented graphical requirement modeling notation [28].
It allows an early requirement engineering analysis in environments where social actors
    Copyright c 2020 for this paper by its authors. Use permitted under Creative Commons
    License Attribution 4.0 International (CC BY 4.0).




                                             23
depend on each other for goals to be achieved, tasks to be performed, and resources to
be furnished [28]. Previous researches proved the relevance and utility of i* to model
organizational requirements of a “multi agent system” [24] facilitating stakeholder’s
interactions by depicting their dependencies and hence providing a mean for coordi-
nation. i* was previously used to model several organizational settings such as online
stores [8], hospital beds management [22,25], health care [28], SCs and more specifi-
cally outbound logistics [21], production support in the steel industry [26] and also for
the development of higher education platforms like collaborative learning software [9]
and MOOCs [23]. The i* framework is divided in two parts providing each a different
level of abstraction: The Strategic Dependency (SD) and the Strategic Rationale (SR)
model [28]. Figure 1 provides the core concepts and icons of the i* framework. The SD
model shows dependencies and the SR model depicts internal intents.

          Legend:                                             D
                                   Goal    Resource                              Some +
                                                        Dependency Link
                                                                            Contribution Link
                         Actor
            Actor
                       Boundary    Task     Softgoal
                                                       Decomposition Link   Means-ends Link




                        Fig. 1. Relevant i* Concepts and their Icons.


    UML Use Case Diagrams are well known to describe the cases in which a system
can be used. UML Sequence Diagrams are a more widely known model that allows to
describe the interactions between the different actors and a central system. This is useful
for blockchain in SC Requirements Engineering (RE) because the Sequence Diagram
can depict a specific order of system operations, which corresponds very well to the
nature of the SC flow. This similarity makes Sequence Diagrams a well-established
candidate to model blockchain initiatives in the SC domain.
    While previous literature has touched upon the adoption of BT for SCM, it has
failed to conceptually model these processes for software engineering. For example,
Niranjanamurthy et al. [12] discuss how blockchain can meet SC objectives and present
a few small case studies to demonstrate how this technology is already used in busi-
nesses. The paper neverhteless includes only superficial process descriptions. Other
research articles, like Saberi et al. [18] and Apte & Petrovsky [1] discuss the use of
blockchain in SC and its benefits and challenges but without providing a case study or
conceptual model. Bettı́n-Dı́az et al. [3], Roa [14] and Casado-Vara et al. [4] provide
exemplary flowcharts, but these only describe a generic implementation of blockchain
in the SC of virtually any company in any industry. Furthermore, Rocha et al. [15] and
Marchesi et al. [11] have tried to model blockchain implementations for a fidelity point
program and for the workings of a university group, by using different UML techniques.
However, both these cases were mostly fictional and limited.
    This paper extends on previous research by Ben Hamadi et al. [5]. The latter paper
studied the use of the i* modeling language for BT in SC for Blockchain-Oriented
Software Engineering (BOSE), based on a case study of a Belgian retail giant. The
study in this paper further investigates and elaborates on this notably by implementing
extensions to i* as proposed by Ben Hamadi et al. [5] but not developed in there; this




                                          24
has been done on a genuine case study. Moreover, the present research additionally
applies UML as a modeling technique. The latter is widely adopted in businesses for
specification stages in software engineering.

2     Research Paradigm, Question and Methodology
Research Paradigm. The research presented here takes roots in the Design Science
paradigm [6]; the latter aims to deliver generic solutions for known (or not yet consid-
ered) problems. The result of a design science research problem can be a solution in
the form an artifact, terminology, methodology, engineering tool, and so forth. In the
present research, we have enriched the i* framework to better match with the prob-
lematic of blockchain as well as applied i* and UML models for BOSE. Strengths and
weaknesses of the models are explored, and a comparison between the frameworks is
presented, based on a set of criteria.
    Research Question. Are extended i* models and UML Use Case/Sequence Di-
agrams appropriate modeling techniques to visualize the organizational structure of
blockchain ecosystems and how do these two frameworks compare?
    Research Methodology. To answer the research question, a case study is required
[17]. The chosen case study is a ‘Farm-to-Fork’ project from a Belgian consultancy
company. ‘Farm-to-Fork’ is a SC tracking prototype that uses blockchain to digitize
the food SC and make it more transparent. The Farm-to-Fork project does not have
any technical documentation available, so all information was gathered through inter-
views. Interviews have been conducted with two experts of blockchain working at the
consultancy company to gather the domain knowledge.
    A first interview was conducted in February 2020 with Interviewee 1 (I1) a blockchain
consultant who has worked on, among others, blockchain projects for the Belgian gov-
ernment. A second interview was conducted in April 2020 with Interviewee 2 (I2) an-
other blockchain expert working at the same company. He provided some additional
insights. Out of the information gathered from the interviews, we have elaborated sev-
eral conceptual models using both i* and UML techniques. A third, final validation
session was organized in May 2020 with I2; the latter then validated and confirmed the
case study description as well as the associated representations. After applying both
modeling techniques to the case study, a summary of their pros and cons is provided.
Comparing both techniques is useful to determine their shortcomings.

3     Case Study
The case study, called Farm-to-Fork concerns a blockchain solution made to track farm
animals throughout the SC process, from “their birth to your plate”. The solution also
includes an easy to use app that gives an overview of the stages of the SC process,
including QR-codes to track animals. Every participant in the network, and therefore
every node in the SC, can quickly check the origin of the animal, the quality and the
different previous steps that the animal has gone through.

3.1   Farm-to-Fork
The Farm-to-Fork prototype was created to meet the increasing expectation levels for
improved transparency in the food industry. This solution provides an answer to many




                                        25
of those struggles. I2 suggests that the most important benefits of this implementation
are the traceability and the liability aspects. Traceability ensures the ability for the SC
participants to closely monitor the animals and allows them to know the exact state
and quality of the animal (product). Therefore, it becomes much easier to detect con-
taminated batches, and to identify any such batches before they can reach the final
SC node (such as supermarkets) where they may create a health hazard to unknowing
consumers. This also helps to reduce waste. Additionally, I2 remarks that, even if a
contaminated product manages to get to consumers, it is much easier to trace down the
specific faulty batches, since all product information is meticulously and individually
stored in the blockchain. Therefore, in case a contaminated batch would still reach the
end-consumers, the health associated consequences will be much less severe.
    The liability aspect that I2 mentions refers to knowing all the actions of the SC
nodes, including their consequences. For example, fragile chicken eggs that are trans-
ported from node to node throughout the SC can break at any stage. However, disputes
can arise between the participants of the SC network about who is responsible for this.
With blockchain, these disputes can be settled very quickly as the database can tell when
and where every individual egg broke. Furthermore, the advantages do not only apply
to the producers, but also to the consumers, since the idea is also to expose a part of the
blockchain to them. Consumers can view information about a specific animal product
in the supermarket by scanning a QR-code. This enables consumers to verify the origin
and all the process steps that the animal has gone through.
    However, it is important to mention that consumers should only have access to re-
stricted, but relevant information. If a consumer would also be able to see exactly how
many chicken eggs they’ve bought from a specific farmer, they might want to skip some
parts of the SC cycle and go straight to that farmer for eggs, leaving the rest of the SC
nodes redundant and unprofitable. I2 underlines the importance to carefully assign spe-
cific access rights to each participant.
    More information about the case study – the type of blockchain and the used raft
consensus – can be found in Appendix I3 .

3.2     Overview of the Farm-to-Fork Blockchain participants
The Farm-to-Fork solution is used in a context of farm animals that go through the SC.
For this paper, the case study takes an in depth look at the logistic flow of chicken meat
from farmer to consumer.
    The possible participants for the blockchain project, their respective roles within
the SC and their minimum required input into the blockchain are listed in Table 1 (the
detail is available in Appendix II). This represents a generic model of how the solution
works in this context. More (or less) participants could be involved, depending on the
needs and context of each specific SC’s structure.

4      Using i* to model the Farm-to-Fork Blockchain
4.1     Proposed Extensions for i* for Modeling Blockchains
Two types of extensions of i* are proposed in this paper: privacy and laws and norms.
 3
     All appendices are available at: http://dx.doi.org/10.17632/zkygycmz2t.1




                                             26
                     Table 1. Farm-to-Fork Blockchain network participants.

  Blockchain    Task                            Input
  participant
  Farmer        Raising chickens.             Characteristics of chickens, the kind of poultry feed
                                              used, the sicknesses of chickens and their antibiotics,
                                              confirmation of number of caught chickens.
  Catcher        Catching the chickens.       Which chickens were caught and in which order.
  Transporter to Transports the chickens from The conditions of the transportation such as the hu-
  butcher        the farm to the butcher.     midity, the temperature, the shipment status.
  Butcher        Prepares the chicken meat.   Number of chickens (slaughtered), treatments, treat-
                                              ment conditions, storage, storage conditions, sizes
                                              and volume of the pieces, quality control.
  Packager       Packs the meat according to The amount of meat, the size and volume.
                 needs of the supermarket.
  Transporter to Transports the chicken meat The conditions of the transportation such as the hu-
  supermarket from the packager to the super- midity, the temperature, the shipment status.
                 market.
  Supermarket Sells the chicken meat to con- Amount of chicken meat and volume sold, stock data,
                 sumers.                      waste data, quality control.

    Bashir [2] and Bettin-Diaz et al. [3] note that, from the various blockchain hurdles,
the privacy issue might be one of the most challenging. The privacy of all nodes in the
network must be respected by restricting access to certain data. The nodes themselves
should be able to determine which information can be accessed by who and what in-
formation should be anonymized. The importance of privacy should not be overlooked.
Therefore, it is recommended that these privacy requirements are explicitly modeled
when visualizing blockchain in SCM. Ben Hamadi et al. [5] proposed to extend the i*
framework by adding the following concepts: access control, privacy accountability,
confidentiality and anonymity but did not implement it, this is done in this paper.
    Next to the privacy issues, I1 also stresses the importance of regulations. As blockchain
is still a relatively young technology, new regulations that limit the working of the
blockchain and/or smart contracts might become applicable. The legal binding of smart
contracts in a court of law is often a subject for debate [2]. I1 specifically refers to
the repercussions of the GDPR regulations on blockchain. Under GDPR, personal data
should remain within the EU. This imposes restrictions on public blockchains because
there is no control on where the nodes are located. I1 mentions that this is less of a
problem with private blockchains. Additionally, the ‘right to be forgotten’ conflicts with
blockchain as an immutable chain of historical transactions, although this rule lacks a
real, strict definition. Currently, a workaround exists whereby personal data is stored
‘off-chain’, outside the blockchain database. A reference and a hash of this data is then
registered in the blockchain. However, this destroys the purpose of the blockchain, since
transparency is diminished, data-ownership becomes vague, one need to find a new way
to integrate data from other participants and the data is more vulnerable to cyber-attacks.
Siena et al. [19] and Siena, Perini, Susi, & Mylopoulos [20] have introduced an i* exten-
sion to model laws and norms. [19] revolves around the application of such extensions
specifically for European food traceability systems. This is particularly interesting for
blockchain in SCM, as it is important for system developers to understand how the




                                               27
blockchain should be compliant with which regulations. Because blockchain is a tech-
nology which steadily becomes more widespread in the IT-landscape, new regulations
will emerge to control it legally.
    Figure 2 provides an overview of all suggested extensions, including their proposed
graphical notations. The i* extensions for privacy concepts and for laws and norms are
taken over from the literature.

           Concept                  Graphical notation                             Description                    References

                                                                 Privacy

                                                                      Access to data in the chain is restricted
                                                                                 to certain nodes.
                                                  L                                                               Ben Hamadi
         Access control                                                 This notation can be used on data           (2020)
                                                                        elements. The annotation allows to
                                        AC                            specify who has access or who doesn’t.

                                                                     The notation is used on a data element
            Privacy                                                      and allows to make third parties         Ben Hamadi
         accountability                                              accountable for data manipulation under        (2020)
                                           PA                                 privacy requirements.

                                                                       The data-owner can hide certain data
                                                                                                                  Ben Hamadi
         Confidentiality                                              from the other nodes. This notation can
                                                                                                                    (2020)
                                             C                              be used on data elements.

                                                                       An actor wants to anonymize his data
                                                                              partially or completely.
                                                  L                                                               Ben Hamadi
          Anonymity                                                     The notation is used on an actor            (2020)
                                                                     element and allows to specify what data
                                                                             should be anonymized.

                                                         Laws and norms



                           Source                        Actor         An actor should be compliant with a
                                           Norm                                                                    Siena et al.
             Norms                                                     certain norm. This norm also has a
                                                                                                                  (2008, 2009)
                                                                                source (e.g. EU).




                                Fig. 2. Proposed Extensions of i* for BOSE.

4.2   Strategic Dependency Diagram – Farm-to-Fork with Blockchain
It should be apparent that, in case of a blockchain adoption for the Farm-to-Fork pro-
cess, all actors will become connected to each other through the blockchain system.
To visualize such a process, the blockchain system itself should also be represented as
an actor, alongside the other participants in the network. The relationship between the
nodes in the SC and the blockchain is indeed a dependent one. The blockchain network
depends on the farmer, the catcher, the transporters, the butcher, the packager and the
supermarket for data. The data is validated and saved into the blockchain. Certain nodes,
like the transporter, can depend on the use of IoT devices to automatically capture and
send data to the blockchain. For the transporter, this data can include the transportation
conditions such as the humidity and the temperature. Based on this data, the blockchain
system can also verify whether the contractual terms are fulfilled. The (execution of the)
smart contracts therefore depend(s) on the data in the blockchain database. The system
can automatically execute the contract through these smart contracts. Because these
smart contracts depend on the input data of the SC nodes in the blockchain database,
they are also represented as an actor.
    Additionally, the blockchain depends on the supermarket to specify the attributes
that must be collected by the various stakeholders as input for the blockchain database.




                                                            28
On the other hand, the supermarket node also depends on the blockchain data itself, to
permit an analysis of the optimal quality requirements (via business intelligence tech-
niques on this data). After the optimal conditions are estimated by the supermarket, the
smart contracts need this list of quality requirements to adjust the contract specifica-
tions. Moreover, consumers can check the product’s history and origin by (partially)
viewing the blockchain’s data. The SD model of such a SC process is shown in Fig. 3.
                               Nodes can only
                                       see the
                                requirements
                                                            AC      Quality
                               of themselves,
                                  not of other                   requirements
                                        nodes                                                 Hide pricing
                                                                                              information



                                                        D




                                                                                D
                                              Smart
                                                                                Supermarket                  Farmer            Catcher        Butcher
                                             contract

                                                                                                D




                                                                                                             D
                                                   D



                                       D


                                                                                D




                                                                                                                 D
                                                   Product                                 Input data




                                                                                                                              D
                             Execute                                  Product quality
                             contracts
                                                 contractual
                                                                        attributes
                                                                                          needed from                                    D
                                                 terms data                               stakeholders                Product PA
                                                                                                                                              Packager
                                                                                                                       data
          Consumers can                                                                                                              D
                 only see                                                                                         C
          limited parts of                              D




                                                                                                                      D
           the Blockchain                    D
                                                                                          D
                                                                           D




                                                                                                         D                               D
                                   AC Origin and                  Blockchain                                 IoT device
                                                                                                                                             Transporter
          Consumer                    history of
                               D       product
                                                        D                                                                 D    Product
                                                                                                                                data




      Fig. 3. Farm-to-Fork Blockchain SD Diagram using Blockchain and Smart Contracts.

    Figure 3 also contains the extensions for privacy concepts. Consumers are only al-
lowed to see a limited part of the blockchain data and process. Next, the quality require-
ments imposed by the supermarket are only distributed to the relevant nodes, depending
on their respective responsibilities within the overall process. The supermarket can also
hide its own price data, since this is classified as sensitive information. All nodes can
specify what data they want to hide from other nodes, and third parties should be held
accountable when given access to manipulate this data.

4.3   Strategic Rationale Diagram – Farm-to-Fork with Blockchain

The SR model focuses more on the internal rationale or reasoning of all the nodes,
related to the dependencies between actors.
    In addition to the interaction between the different SC participants, the supermar-
ket’s ability to specify the quality requirements for each stakeholder is also important
and is therefore depicted with the SR model in Figure 4. This model focuses on the
interdependencies between the supermarket, the blockchain, the smarts contracts and
the consumer. The supermarket is an especially important node as the final product
arrives here and is sold to consumers. Hence, the chicken meat must be of the best
quality in order to sell it to consumers. It is likely that most benefits of the blockchain
adoption are experienced in this stage of the SC: no more wastage because of higher
quality and avoidance of contaminated products, contaminated products can no longer
get into the hands of consumers which limits health risks, and consumer awareness is
higher because they can scan the QR-code on the packaging of the chicken meat to
check the history of the product. Given these four important actors (the supermarket,




                                                                                    29
the blockchain, the smart contracts and the consumer), the SR model can understand
the ‘why’ of interdependencies.
                                                                                                        D

                                                                                                        D                                                   Chicken
                                                                                Quality                                                                    meat ready               Payment
            Supermarket
                                                                             requirements                                                                    to eat
                                   Increase                                                                        Execute                                                          D




                                                        D




                                                                                                                                                                   D
                                 profit margin                                                                     contract                 Smart
             Increase sales                              Increase sales                                                                    contract
                 through                                 through waste




                                                                                            D
                customer                                    reduction
                                                                                                                        Check whether                         Consumer
               awareness          Increase sales                                                     Adjust
                                                                                                                          contractual
                                   through good                                                     contracts            terms fulfilled
                                  quality chicken                      Good quality
                                                                         chicken                                                                                                Verify product




                                                                                            D
        Store product                                                                                                                                                            authenticity
            data                                                                                       Compare terms
                                        Set quality
                                       specification                                                    to Blockchain
                                                                                                             data                                                  Check product
                                                                                                                               Check                                 origin and
                                                                                                                           Blockchain data                            history
         Analyze
         product                                                Communicate
                              Find optimal
        conditions                                                optimal
                                product
                                                                conditions to
                               conditions
                                                                   nodes                                                                   D




                                                                                                                                                                         D
                                                        D                                                                                      Product
      D




                                                                                                                                             contractual
                              Apply BI to                                                                       Execute                      terms data                Origin and
                              Blockchain
                                                                                         Input data                                                                    history of
                                                                                        needed from             contracts                                               product
                                 data
                                                                                        stakeholders
                                                                  D
                                                                                        Product




                                                                                                                                               D
                                                                                        quality

                                                                                                                D
                                                                                       attributes
                                                                  Product                                       D




                                                                                                                                                    D
                                                                   data
                           Protect
                                                                                                                                                       Store
                        personal data                                                                                                              transactional
                                                                                            D
                                                                                                                                                       data
                                                                                                            D




      Guarantee right
      to be forgotten
                                                 Fair and                                                                       Store specific
                                             transparant data                                                                  data input from
                                                processing                                                                         nodes

        Store data only
                                                                      GDPR             EU                    Blockchain
       when neccesary for               Keep data
           purpose                      within EU



                         Ensure data
                      integrity, security
                     and confidentiallity




           Fig. 4. Farm-to-Fork Blockchain SR Diagram to Specify Quality Requirements.

    The original i* extension to describe regulatory compliance was specifically tar-
geted towards the SR type of models in i*. Figure 4 shows the integration of the EU
GDPR law in the SR model. The overall aim of the regulation is to protect personal
data. As shown in Figure 4, this can be achieved through guaranteeing the ‘right to be
forgotten’, keeping data processing transparent, only recording data when necessary,
keeping the data within the EU and ensuring data integrity, security and confidentiality.

5     Using UML to model the Farm-to-Fork Blockchain
5.1    UML Use Case – Farm-to-Fork
The Use Case diagram is depicted in Figure 5. All network nodes can input, store and
verify data. The verification of data can only be fulfilled when a leader is appointed in
the Raft consensus mechanism (see Appendix I), although every node will double check
the verification of the leader (I2). Additionally, the supermarket can provide quality
specifications that must be adhered to by all parties. Here, smart contracts are shown as
an actor even though they are an integrated part of the blockchain system. This is done




                                                                                            30
to show the possible actions of the smart contracts (i.e. checking whether contractual
terms are fulfilled or not and automatically executing the smart contracts). Moreover,
consumers can check the history and origin of products by scanning a QR-code.

                                                    Blockchain
                                                                 Provide quality
                                                                  specification

                         Input Data
        Farmer                                                                                    Supermarket




       Catcher           Store Data
                                                                                                   Packager




                                                                   Check whether contractual
                                                                       terms are fulfilled
      Transporter         Verify Data
                                                  Execute smart contract
                                                                                               Smart contracts
                         <>

                                                                 Check product history
                          Participate in voting                       and origin
                           for a Raft leader
       Butcher
                                                                                                 Consumer



                    Fig. 5. Farm-to-Fork Blockchain Use Case Diagram.

5.2     UML Sequence Diagram – Farm-to-Fork
The Sequence Diagram is modeled because it shows the order in which the activities
occur. As already mentioned previously, this is especially useful for SC processes. The
Farm-to-Fork Sequence Diagram is depicted in Figure 6.
    With every blockchain return message ‘Verification of data’, an alternative fragment
should take place, which defines what happens if the verification is successful and what
happens if it isn’t. However, for simplicity reasons in Figure 6, this alternative (or alt-)
fragment is only explicitly modeled for the first occurrence where the blockchain wants
to verify data (i.e. at the farmer’s data entry). Thus, although not explicitly modeled,
this alt-fragment takes place every time the blockchain wants to verify data.
    As mentioned before, the transporter can use an IoT device to automatically save
and send transportation data to the blockchain. This proposed IoT device is also in-
cluded in the Sequence Diagram to show the effects of the implementation. Finally,
at the bottom, a loop is included. This represents the quality requirement updates that
the supermarket can repeatedly implement whenever a new (local or global) optimum
is found for the process conditions (e.g. by using business intelligence tools). More
illustrations of sequence diagrams in the context of blockchain use cases (on the raft
consensus and customer access) can be found in Appendix III.

6      Evaluation of i* and UML for modeling BOSE in SCM
This section compares the pros and cons of the SD and SR models (i* framework) ver-
sus the Use Cases and Sequence Diagrams (UML) as modeling techniques for BOSE.




                                                    31
 Fig. 6. Farm-to-Fork Blockchain Sequence Diagram (see the Appendix for complete version).


First, a set of the criteria to compare both models is defined. The criteria are based on
three intakes: generic modeling criteria based on existing literature [7,16]; blockchain-
specific criteria defined in consultation with blockchain expert (I2), and other criteria
based on findings from applying both modeling techniques. Next, both frameworks are
evaluated using these criteria. Detailed discussions on each criterion of both languages
can be found in the Appendix IV. Table 2 provides a final evaluation.
    As can be seen in Table 2, the two frameworks distinguish themselves by their dif-
ferent purpose: while i* is social-focused, the UML Use Case and Sequence Diagrams
are system-oriented. Both techniques are complementary. Therefore, we recommend to
use the i* framework during the early phases of RE. This enables system developers
to understand the ‘why’ of the SC process, giving a clear overview of the interdepen-
dencies and the goals of all nodes in the blockchain network, as this is the core of the
blockchain’s decentralized system. During later phases, UML diagrams can be applied
to design the system’s interactions with the different actors of the SC in more detail.

7   Conclusion
After applying both modeling languages to the case, a comparative evaluation between
both approaches was performed. A set of assessment criteria was established and we
conclude on the complementarity of the approaches. The in-depth comparison between
both has revealed that they also lack some elements to model BOSE in SCM to its full
extent. Hence, new graphical concepts are proposed to enhance the models. First, in line




                                         32
                      Table 2. Comparison of i* and UML for modeling BOSE in SCM.

 Criteria                   Description                                                          i* UML
                                                  Generic
 Coverage of elements        Whether certain things are difficult or impossible to express. This - +
                             is about the completeness of the available elements.
 Reusability                 Whether models can be reused in a different context.                + +
 Guidelines      and   tool- Whether clear guidelines and tools for the model are available.      - +
 support
 Widespread in different ar- Whether the modeling technique is standardized and generally - +
 eas                         adopted.
                                             Expert opinions
 Restricting access and pri- Whether the model can include privacy concerns.                      -  -
 vacy concepts
 Scalability                 Whether the model is scalable.                                       - +
 Ability to express work- Whether a flow or structure can be defined in the model.                - +
 flow patterns
 Norms                       Whether the model can include the compliance of norms and regu- -       -
                             lations.
                                               Other Criteria
 Social focus                Whether the model can represent the actor’s intentions and internal + -
                             reasoning.
 Dual granularity            Whether the model allows for both a high-level and a more detailed + +
                             view of the system.
 Flexibility in modeling     Whether the model is not ‘deterministic’ but allows to model dif- + -
                             ferent scenarios.
 Technical concepts          Whether the model has notations to introduce technical concepts. - +

with Ben Hamadi et al. [5], this paper recommends the inclusion of privacy concepts.
Next, because of the importance of laws and upcoming regulations that will determine
the future direction of BT, the enhancement of the i* framework for laws and norms is
also recommended.
    The present study combined with Ben Hamadi et al. lead us conclude that i* and its
refinements are relevant for each BOSE development in SCM. Future work includes (i)
the application of the enhances i* framework in other domains, (ii) the application of
other frameworks line notable the business use case model together with BPMN (see
[27]) and (iii) the development of transformation (forward engineering) rules to support
the blockchain implementation with object and agent technology.

References
 1. Apte, S., Petrovsky, N.: Will blockchain technology revolutionize excipient supply chain
    mgmt.? Journal of Excipients and Food Chemicals 7(3), 910 (2016)
 2. Bashir, I.: Mastering blockchain. Packt Publishing Ltd (2017)
 3. Bettı́n-Dı́az, R., Rojas, A.E., Mejı́a-Moncayo, C.: Methodological approach to the definition
    of a blockchain system for the food industry supply chain traceability. In: Intl. Conf. on
    Computational Science and Its Applications. pp. 19–33. Springer (2018)
 4. Casado-Vara, R., Prieto, J., De la Prieta, F., Corchado, J.M.: How blockchain improves the
    supply chain: Case study alimentary supply chain. vol. 134, pp. 393–398. Elsevier (2018)




                                                33
 5. Hamadi, Y.B., Heng, S., Wautelet, Y.: Using i*-based organizational modeling to support
    blockchain-oriented software engineering: Case study in supply chain mgmt. In: The Intl.
    Research & Innovation Forum. Springer (2020)
 6. Hevner, A.R., March, S.T., Park, J., Ram, S.: Design science in information systems research.
    MIS Q. 28(1), 75–105 (2004)
 7. Kelemen, Z.D., Kusters, R., Trienekens, J., Balla, K.: Selecting a process modeling language
    for process based unification of multiple standards and models. Tech. rep. (2013)
 8. Kolp, M., Wautelet, Y., Faulkner, S.: Sociocentric design of multi-agent architectures. In:
    Social Modeling for Requirements Engineering. MIT Press (2011)
 9. Kolp, M., Wautelet, Y.: Human organizational patterns applied to collaborative learning soft-
    ware systems. Computers in Human Behavior 51, 742–751 (2015)
10. Kshetri, N.: 1 blockchain’s roles in meeting key supply chain mgmt. objectives. Intl. Journal
    of Information Mgmt. 39, 80–89 (2018)
11. Marchesi, M., Marchesi, L., Tonelli, R.: An agile software engineering method to design
    blockchain applications pp. 1–8 (2018)
12. Niranjanamurthy, M., Nithya, B., Jagannatha, S.: Analysis of blockchain technology: pros,
    cons and swot. Cluster Computing 22(6), 14743–14757 (2019)
13. OMG: Omg unified modeling language (omg uml). version 2.5.1. Tech. rep. (2017)
14. Rao, N.: The time is now. Quality Progress 51(10), 18–23 (2018)
15. Rocha, H., Ducasse, S.: Preliminary steps towards modeling blockchain oriented software.
    In: WETSEB2018. pp. 52–57. IEEE (2018)
16. Ruiz, F., van Harmelen, F., Aben, M., van de Plassche, J.: Evaluating a formal modelling
    language. In: EKAW1994. pp. 26–45. Springer (1994)
17. Runeson, P., Host, M., Rainer, A., Regnell, B.: Case study research in software engineering:
    Guidelines and examples. John Wiley & Sons (2012)
18. Saberi, S., Kouhizadeh, M., Sarkis, J., Shen, L.: Blockchain technology and its relationships
    to sustainable supply chain mgmt. Intl. J. of Production Research 57(7), 2117–2135 (2019)
19. Siena, A., Maiden, N., Lockerbie, J., Karlsen, K., Perini, A., Susi, A.: Exploring the effec-
    tiveness of normative i* modelling: Results from a case study on food chain traceability. In:
    CAiSE2018. pp. 182–196. Springer (2008)
20. Siena, A., Mylopoulos, J., Perini, A., Susi, A.: Designing law-compliant software require-
    ments. In: International Conference on Conceptual Modeling. pp. 472–486. Springer (2009)
21. Wautelet, Y.: Representing, modeling and engineering a collaborative supply chain manage-
    ment platform. Intl. J. of Info. Systems and Supply Chain Mgmt. 5(3), 1–23 (2012)
22. Wautelet, Y.: A model-driven IT governance process based on the strategic impact evaluation
    of services. J. Syst. Softw. 149, 462–475 (2019)
23. Wautelet, Y., Heng, S., Kolp, M., Penserini, L., Poelmans, S.: Designing an mooc as an agent-
    platform aggregating heterogeneous virtual learning environments. Behaviour & Information
    Technology 35(11), 980–997 (2016)
24. Wautelet, Y., Kolp, M.: Business and model-driven development of BDI multi-agent systems.
    Neurocomputing 182, 304–321 (2016)
25. Wautelet, Y., Kolp, M., Heng, S., Poelmans, S.: Developing a multi-agent platform sup-
    porting patient hospital stays following a socio-technical approach: Mgmt. and governance
    benefits. Telematics and Informatics 35(4), 854–882 (2018)
26. Wautelet, Y., Kolp, M., Penserini, L.: Service-driven iterative software project mgmt. with
    i-tropos. J. UCS 24(7), 975–1011 (2018)
27. Wautelet, Y., Poelmans, S.: An integrated enterprise modeling framework using the
    RUP/UML business use-case model and BPMN. In: The Practice of Enterprise Modeling
    PoEM 2017, Leuven, Belgium, Proceedings. LNBIP, vol. 305, pp. 299–315. Springer (2017)
28. Yu, E., Giorgini, P., Maiden, N., Mylopoulos, J.: Social Modeling for Requirements Engi-
    neering. MIT Press (2011)




                                            34