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  <front>
    <journal-meta />
    <article-meta>
      <title-group>
        <article-title>Value-Based Security Requirements in a Highly Decentralized Digital Ecosystem: the MUSIC360 Case</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Arthur Mclaren</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Yulu Wang</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Charlotte van de Velde</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Ed Green</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Roel Wieringa</string-name>
          <xref ref-type="aff" rid="aff0">0</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Jaap Gordijn</string-name>
          <xref ref-type="aff" rid="aff1">1</xref>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>The Value Engineers</institution>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Vrije Universiteit Amsterdam</institution>
          ,
          <country country="NL">The Netherlands</country>
        </aff>
      </contrib-group>
      <abstract>
        <p>Security requirements in digital ecosystems should be first and foremost driven by the notion of economic value. Attackers are interested in objects of value, which are exchanged between actors in a network of organizations and end-users. We explain how we derive data-oriented security requirements by means of high level goals, a value model representing the ecosystem, and a data model detailing the value model. The approach is illustrated and validated in a complex ecosystem in the music sector.</p>
      </abstract>
      <kwd-group>
        <kwd>eol&gt;ecosystem</kwd>
        <kwd>security requirements</kwd>
        <kwd>music</kwd>
        <kwd>conceptual modeling</kwd>
      </kwd-group>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>Many innovative services are ofered by digital business ecosystems (DBEs). We define a DBE as a
system of economic actors that depend on each other for their survival and well-being [1]. A DBE has
an associated value network which explains what actors trade with each other.</p>
      <p>
        One such innovative ecosystem is the EU Horizon Europe MUSIC360 ecosystem1, which aims at
providing insights into the value of music to (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ) creatives (performers and authors of music), venues
(restaurants, retail shops, ofices), and policymakers (EU oficials, national authorities and lobbyists).
The MUSIC360 ecosystem provides data about the value of music, where ‘value’ can have an economical,
societal, or cultural connotation. To do so, MUSIC360 collects data about music used in venues (e.g. by
installing music finger-printing devices in venues to discover what is actually played), efects of music
played (for example increased revenue), and meta data of music such as rightholders (performers and
authors) and earnings by rightholders. Important players are the collective management organizations
(CMOs). They collect money from venues in return for a license to play music and pay the money
subsequently (minus an administrative) fee to the right holders). This data should be protected for
reasons of privacy, but also misuse of data by hyperscalars such as Google, Amazon, Meta, and Alibaba
should be discouraged.
      </p>
      <p>We will protect privacy-sensitive data by means of access controls. More dificult is the prevention of
misuse by hyperscalars. The risk is not so much unauthorized access but taking over the full ecosystem
by one of these hyperscalars. We mitigate this risk by constructing a very decentralized way ecosystem
and also employ decentralized governance in which power and decision taking is well balanced. This
makes it more dificult to buy the complete ecosystem,</p>
      <p>All this implies that we have to design a highly decentralized platform that still should behave in
an integrated way, where parties remain in control of their own data, but nevertheless can together
present a coherent view on the value of music, and privacy is respected. This paper presents the
requirements engineering process to achieve such a highly decentralized, privacy preserving ecosystem,
and evaluates it. The focus is on security requirements, which are about access controls for data stored.
The contribution of this paper is that we show how to base security requirements and policies on the
value produced, distributed and consumed in a digital ecosystem.</p>
      <sec id="sec-1-1">
        <title>1.1. Contributions</title>
        <p>This research aims to contribute twofolds:
• Methodology This paper introduces a value-driven approach to security requirements
engineering, where security measures are based on the economic value exchanged in a decentralized
ecosystem. By combining the e3value model with UML class models, the methodology ensures
that security is aligned with stakeholders’ valuable assets and interests.
• Case Study The MUSIC360 ecosystem is used as a case study to demonstrate and validate this
methodology. It shows how this approach works in practice within a multi-actor environment,
highlighting the benefits and challenges of applying value-based security in real-world settings.</p>
      </sec>
      <sec id="sec-1-2">
        <title>1.2. Research problem</title>
        <p>The research problem addressed in this paper is the challenge of establishing security requirements
and policies within a digital ecosystem based on the value that is produced, distributed, and
consumed. This approach shifts the focus from traditional security models to one that is more
aligned with the economic dynamics of digital ecosystems, aiming to enhance the relevance and
efectiveness of security measures by tying them directly to the flow of value within these environments.</p>
        <p>This paper is structured as follows. In Sec. 2 we discuss related security requirements engineering
approaches. Then, in Sec. 3 we discuss our value-based security requirements engineering approach,
followed by the goals of the ecosystem (Sec. 4), the value model (Sec. 5), the IT architecture (Sec. 6), and
the structure of the data to be secured (Sec. 7). Finally in Sec. 8, we evaluate our approach and present
conclusions (Sec. 9).</p>
      </sec>
    </sec>
    <sec id="sec-2">
      <title>2. Related Work: Security Requirement Engineering</title>
      <p>Security Requirement Engineering (SRE) is a critical domain in the development of secure software
systems/platforms. It involves the identification, analysis, specification, and validation of security
requirements to ensure that software systems are robust against threats and vulnerabilities [2].
Methodologies include Goal-Oriented Requirement Engineering (GORE) [3] frameworks such as KAOS and i*.
According to the comparative work done by [4], the KAOS framework systematically derives security
goals and refines them into operational requirements and constraints, while the i* framework models
organizational environments and relationships to identify and mitigate threats through goal refinement
and actor dependency analysis.</p>
      <p>Misuse and abuse cases are also a way to conduct a security requirement analysis which focuses
on capturing and modeling systems’ unauthorized use, introduced by [5] and further developed by
[6]. This method develops negative scenarios by modeling potential threats and attacks, aiding in
the identification of security requirements. Risk-based approaches like the CORAS methodology and
OCTAVE provide model-based and comprehensive risk assessment frameworks, respectively, to align
security requirements with identified risks [7].</p>
      <p>These frameworks can be integrated into the systematic processes provided by tools like Secure
Tropos and SQUARE (Security Quality Requirements Engineering), which ofer structured processes for
integrating security requirements into the development lifecycle. Secure Tropos incorporates security
concerns into early development stages using actor-based models [8], while SQUARE involves a
ninestep process for eliciting, categorizing, and prioritizing security requirements [9]. Ansari et al. present
the STORE methodology for security requirement elicitation, which emphasizes early identification of
security threats during the software development process [10]. Additionally, Maskani et al. advocate
for a comprehensive approach to SRE that reconciles diferent perspectives on security requirements,
such as user, threat, and goal perspectives [11].</p>
      <p>In contrast to traditional goal-oriented approaches, we propose deriving security requirements based
on the concept of economic value. This approach directly links security needs to the valuable assets
within the ecosystem, addressing the challenges of securing decentralized systems where multiple
stakeholders interact. By focusing on economic value, our method ensures that security is implemented
in areas where stakeholders have the most at risk, such as sensitive data, intellectual property, and
ifnancial transactions.</p>
    </sec>
    <sec id="sec-3">
      <title>3. Towards a secure and decentralized MUSIC360 ecosystem</title>
      <p>We propose in Fig. 1 a step-wise approach to find security requirements in ecosystems, to protect data,
and to keep data ownership at the data owners in order to prevent misuse of the data by for example
hyperscalars.</p>
      <p>Our approach begins by identifying the high-level goals of the ecosystem, which are then linked to
the economic value exchanged among stakeholders. Using the e3value model, we map out the flow of
value and the actors involved, ensuring that each step of the process accounts for the security needs
of these stakeholders. This value model is then integrated with UML class models to detail the data
structures involved, while security requirements are systematically elicited and documented based on
these models. This process is applicable both within the MUSIC360 ecosystem and more broadly to
other decentralized systems, allowing for flexibility and scalability.</p>
      <p>An essential element of our approach is that we elicit a value model of the ecosystem, cf. the e3value
[12] method. The reason for this is the following: an e3value model focuses on what actors exchange
between each other, in terms of value objects. These objects may represent money, but also other
valuable things, such as data or mandates to exploit music. The actors in an e3value model show the
afected parties, e.g. if data is stolen, and the value objects represent what can be stolen. Usually,
attackers are only interested in things of value (e.g. kinds of data they can resell). Hence, we argue that
each security requirements engineering process should elicit a value model in an early stage, to identify
what is of value to whom.</p>
      <p>The high-level security requirements, the e3value model, and requirements of other categories
(outof-scope for this paper) are the input for the design of the IT architecture.</p>
      <p>The MUSIC360 ecosystem is specifically concerned with protection of the data in the system, e.g.
to prevent theft of data or abuse of data by hyper-scalars. To this end, we have defined a specific
sub-process for data security requirements. Using the e3value model as input, data requirements are
elicited (e.g. what kinds of data will be stored by the system) and represented as a UML class model.
This class model is the primary source for finding data security requirements. These are used to define
data access controls, which are efectively access policies per data element.</p>
      <p>The process ends with a (prototype) implementation that can be validated by the MUSIC360 actors.</p>
      <p>Each activity requires two or more workshops with the relevant stakeholders to find the requirements
and create the design. In the remainder of this paper, we illustrate each step in the process further.</p>
    </sec>
    <sec id="sec-4">
      <title>4. MUSIC360 Goals</title>
      <p>The MUSIC360 project goals are already stated in the project proposal to the EU, and was the result of a
number of workshops with the partners involved. To make the paper self-contained, we briefly review
the requirements below:
• G1: A fair distribution of neighboring and author rights based on the actual use of music. For the</p>
      <p>
        MUSIC360 project, two intellectual property rights are relevant: (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ) the neighboring right which
      </p>
      <p>
        results from playing music in public, e.g. a restaurant or a shop, and (
        <xref ref-type="bibr" rid="ref2">2</xref>
        ) the author right which is
the result of written lyrics and scores by an author.
• G2: Establish a method to value music, such that is usable to motivate a ‘fair compensation’ for
the use of music. The law prescribes that if music is played in public, rightholders are entitled to
a fair compensation, without actually stating what ‘fair’ actually is. MUSIC360 argues that fair
compensation should be based on the value of music for its users.
• G3: Wide and transparent availability of information concerning the value of music respecting
confidentiality requirements. Currently, information about the (value of) music is available in a
fragmented way, e.g. at record labels, collective management organizations (CMOs), companies
measuring the actual use of music, and the rightsholders themselves. MUSIC360 wants to make
this information available in a consistent and integrated way, which is given the state-of-the-art
in the music industry a problem by itself. However, quite some information is privacy sensitive,
e.g. the rightsholders of a particular recording, what their earnings are, and also the price of
the licenses venues have to pay to CMOs. It is clear that this last goal embodies an important
security requirement, namely that information about music should only be available to the right
stakeholders. Consequently, in this paper, we continue with this last requirement.
      </p>
    </sec>
    <sec id="sec-5">
      <title>5. Ecosystem value model</title>
      <p>After stating the high-level goals, we elicit and design a value model cf. the e3value modeling language
[12]. This value model not only highlights the flow of assets but also serves as the foundation for
deriving security requirements. By focusing on valuable assets like rightsholder earnings and license
data, the value model ensures that security measures are prioritized for areas of high economic risk.
The security requirements in Sec.6 are directly tied to the value exchanges illustrated in the model,
ensuring that each requirement addresses the protection of economically significant assets. For this
case, we follow a normal elicitation process for e3value models, as explained in [14]. For reasons of
brevity, we immediately present the resulting e3value model in Fig. 2.</p>
      <p>
        At the top, venues such as shops and restaurants pay for their license to play music in public. They
always pay for this license to the collective management organization (CMO) in their country. Then
two things can happen: (
        <xref ref-type="bibr" rid="ref1">1</xref>
        ) if the CMO member (performer or author) is in the same country as the
collecting CMO, money is paid by that CMO to the CMO member, or (
        <xref ref-type="bibr" rid="ref2">2</xref>
        ) if the CMO member is in
another country, the money is transferred to the claiming CMO of that country, who subsequently pays
the CMO member. This captures the essential operations of CMOs.
      </p>
      <p>CMO members can use the MUSIC360 platform to access data they are interested in: e.g. data about
tracks played (containing both recordings and music works), playlist data, and also data about their
revenue. CMOs also have access to similar data about their members, and about usage data in other
countries than the one they represent. Finally, there are value-adding companies, such as music branding
companies. They curate playlists with the intention of creating brand awareness through music in a
venue. Similarly, there are market research companies who, on behalf of venues, do experiments to
ifnd out whether music indeed adds value (e.g. increased revenue) for the venue. These parties need
data support for experiments, e.g. monitoring of what is played in a venue. Additionally, they need
metadata on the music, e.g. its genre, tempo, language used, etc.</p>
      <p>Services are provided by the MUSIC360 platform. This is modeled as a single actor, but in reality
reflects the coalition of its members, including the required governance. The precise structure is under
design, but we foresee that the platform at least consists of CMOs, and other data providers, such as
audio recognition companies.</p>
      <p>The e3value model is useful for eliciting security requirements in a number of ways. First, it shows
the actors (profit-and-loss responsible parties). Since actors have an economic value perspective by
definition, for security considerations it is important to distinguish them. If a security breach occurs, or
data is misused by hyper scalars, the actors in the e3value model are the victims. Second, the e3value
model gives a first glance on the valuable assets, because value objects such as ‘access to track data’
and ‘playlist data’ are valuable objects by definition and hence subject to attacks.</p>
    </sec>
    <sec id="sec-6">
      <title>6. IT Architecture</title>
      <p>We perform a normal requirements elicitation process for architectural requirements using several
workshops with all stakeholders involved. This results in a list of requirements, which we summarize
below:
• R1: The MUSIC360 ecosystem should support multiple parties of diferent stakeholder
types, namely creators (performers and authors of music), collective management organizations
(CMOs) who collect money for the public use of music on behalf of the creators, venues (the users
of music), policy makers, and commercial entities who make music available (e.g. Spotify or other
streaming parties). Most of these parties come from the e3value model. Others (e.g. streaming
parties) have been added later in the process and should be fed back into the e3value model.
Solution: Diferent parties, such as creators, venues and policymakers can access the MUSIC360
ecosystem via a browser, which serves as client. The browser communicates via the OAuth 2.0 /
OpenId Connect protocol [15] and REST services [16] with the rest of the components. Each of
these backend components can be provided by a single party.
• R2: The data owner remains in control with respect to its own data. One of the critical
success factors for the MUSIC360 platform is that all parties, specifically those who own data, remain
in control with respect to their data. Most parties have data that is private and competitively
sensitive.</p>
      <p>– R2.1: Data is available to a user if they possess clearly defined access rights that align
with their role in the ecosystem. Data is stored in databases which are under control of
the data owner (e.g., physically hosted at the premises of the data provider trusted to the
owner, or in a data centre, still under control of the data owner). Access to data should be
restricted at least at the instance level (e.g., a recording, work, rightsholder), and preferably
at the property level (earnings of the recording, use of the recording). Solution: Access to
data is controlled by two complementary approaches. First, data access is restricted by using
other data in the databases. For example, performer X may only access its own recordings
and music works. This often referred to as Attribute Based Access Control (ABAC) [17].
Second, data can have Access Control Lists (ACLs). These lists relate data to a user or group
identifier, which is compared to the authenticated user. This is called Discretionary Access
Control (DAC) [18]. Together, these mechanisms are highly flexible access control solutions
and are implemented as policies in the database management system.
– R2.2: Data owners may delegate access control management to others. An example
of this scenario is a creative entity which allows their representing CMO to make its data
available under certain conditions. Often this data is clustered and enriched with additional
metadata. In this scenario, the CMO is responsible for data storage and access control on
behalf of the creative entity. Solution: The architectural solutions allows data owners such
as CMOs to stay in control of their own data, but they may also outsource parts (e.g. the
authentication server) to a trusted party with an appropriate legal contract.
– R2.3: Data owners can make data available in an inaccessible, containerized way
(that is: someone who tries to access the data cannot read the data, but with a set of allowed
predefined operations users can do calculations on the data (e.g. arithmetic operations)).
The result of the operations can be inspectable or not, depending on the use case. It allows
to make data available to untrusted parties, without disclosing the data, but allowing them
to do some controlled operations on the data. Solution: We do not solve this requirement
in this paper but come back to it in Sec. 9 concerning Future Work.
• R3: Authentication should be done by entities owning the data. As data owners should
remain in control, they should also authenticate users of the system. Data owners may decide to
trust each other authentication services. Also, they may decide to trust an external authentication
party such as Google or GitHub. As data owners trust the other authentication providers,
misbehaving authentication providers are not considered as an attack vector. Solution: Each
data owner operates an authentication server cf. OAuth 2.0 / OpenID Connect to authenticate
users to its own data.
• R4: Data of diferent stakeholders should be properly isolated . This means that parties
(specifically data providers), cannot see the data of the other MUSIC360 participants. Solution:
Depending on the data storage solution chosen, this requires specific measures. In others words,
all data will not be stored in one database, where all the data owners have full access to.
• R5: The MUSIC360 system should be as open as possible. Solution: From a technical
perspective, this implies the use of (de-facto) open standards.
• R6: The MUSIC360 system should be scalable, with respect to the number of users and the
amount of data. Solution: The vast majority of data operations are READ operations, meaning
that data enters the system once, and is queried many times. This allows for replication and/or
partitioning of the very large data set, hence distributing data over a large number of decentralised
databases and hardware.</p>
      <p>The most important security requirements for this paper are based on R1, R2, R3 and R4. We have
also discussed the other requirements because it explains some choices made for the architecture.</p>
    </sec>
    <sec id="sec-7">
      <title>7. Data security requirements and access controls</title>
      <p>Data model. To understand the security requirements with respect to stored data, we first have to
know the structure of the data itself (for MUSIC360, we do not use unstructured data). The e3value
model provides hints concerning the data elements, such as track data, country/geographical segment,
rightsholder, work, recording, playlist, license and mandate. However, an e3value model is meant to
understand the actors involved in an ecosystem, and what they exchange of value with each other.
Therefore, for a detailed analysis of the data required, we executed a data modeling task using standard
UML class modeling. This efort takes several workshops, and results in a data model in Fig. 3.</p>
      <p>For reasons of brevity, we explain the most important elements. Rightsholders (e.g. performers or
authors) have claims on a creation (either a recording or a work). Rightsholders can transfer their
claim to a beneficiary and can use an agent to represent them. Collective management organizations
(CMOs) collect compensations for usage of claimed intellectual property rights by venues. CMOs have
a mandate for creations (often recordings) which are played, usually as part of a performed playlists by
venues (shops, restaurants, etc.). These venues have a license to do this, which they obtain from a CMO.
Plays are monitored by a company, called the monitor, doing identification of the played recording of
work. One or more plays of a recording or work result in earnings, via a claim, for the rightsholder.
Data security requirements.
the following steps:</p>
      <p>We elicit the data security requirements in several workshops using
• Stakeholder identification . The stakeholders are based on the actors in the e3value model and
further detailing in the UML class model. There are CMO members (rightsholders, beneficiaries,
and their agents), CMOs themselves, and venues.
• Asset identification . Also, assets are based on the e3value model and the UML class model (see
Table 1). Some classes in the UML are so-called non-assets meaning that there are no access
restrictions, mostly because it concerns publicly available data (see Table 2).
• Determination of access. Finally, using the identified stakeholders, and the identified assets,
we systematically elicit the required and allowed access rights using a series of workshops. In
Access Controls. Access controls are expressions that determine who can access which data. They
are directly based on Table 3 and similar tables for the other assets. Access controls are part of the
database. More precisely, we use Row Level Security (RLS) policies which determine, based on attributes
such as the user identifier, the data elements someone is allowed to read. The design of the access
controls therefore concerns the transformation of all asset access conditions as defined in Table 3 and
results in RLS policies. Given that there is a one-to-one correspondence between the assets and the
relational model in the database, this is a straightforward task.</p>
    </sec>
    <sec id="sec-8">
      <title>8. Evaluation</title>
      <p>We evaluate our approach designing a data-secure architect using the following criteria:
• Connection Between Value Model and Security Requirements
1. represents a Representation that represents the Rightsholder, or
2. represents a Representation that represents a Rightsholder who
owns a Claim connected to a Creation connected to a Claim that
is owned by the Rightsholder
1. represents a Mandate that justifies a Claim owned by the
Rightsholder, or
2. represents a Mandate that justifies a Claim owned by a
Rightsholder who owns a Claim connected to a Creation connected to a
second Claim that is owned by the Rightsholder
no access
• Correctness and completeness
• Efectiveness and eficiency
• Ease of implementation.</p>
      <p>They have been validated with the stakeholders, through internal review, and with the developers
respectively.</p>
      <sec id="sec-8-1">
        <title>8.1. Connection Between Value Model and Security Requirements</title>
        <p>The value model introduced in Sec. 5 (Fig. 2) is central to understanding how security requirements are
derived in the MUSIC360 ecosystem. The value model outlines the economic exchanges between key
actors, such as venues, CMOs, rightsholders, and other participants, highlighting the valuable assets
at stake, including data, money, and rights. These economic flows inform the security requirements,
ensuring that they protect valuable assets from potential threats.</p>
        <p>Rightsholder Earnings Protection. One of the key assets identified in the value model is
the rightsholder earnings (Sec. 5). Rightsholders receive compensation for the public use of their
music, with the flow of funds moving from venues through CMOs to the rightsholders. The security
requirement in Sec. 7 ensures that only relevant stakeholders, such as rightsholders and their authorized
agents, can access this sensitive earnings data.</p>
        <p>The value model illustrates the economic flow, showing how earnings travel through the ecosystem,
which directly informs the access control policies in R2.1 and R2.2. For instance, only rightsholders or
their representatives can view their earnings, while CMOs are limited to viewing data relevant to their
members. This structure reflects the economic relationships shown in the value model and ensures that
ifnancial data is protected according to the stakeholders’ interests.</p>
        <p>License and Usage Data Security. In the value model, venues (e.g., shops and restaurants)
pay for licenses to publicly play music, with those payments flowing to CMOs. The license data and the
usage data collected by monitors are essential for determining rightsholders’ compensation. The value
model illustrates the data exchange between monitors, CMOs, and venues, highlighting these as critical
assets.</p>
        <p>As a result, the security requirements ensure that only venues with valid licenses can access their
specific license fee and usage data, safeguarding commercially sensitive information. Additionally,
monitors have restricted access to this raw data, preventing them from unauthorized use or resale,
which aligns with the concern of protecting valuable data from hyperscalars, as noted in R2.3.
Multi-Actor Governance and Data Control. The multi-actor nature of the MUSIC360 ecosystem,
highlighted in the value model, means that diferent stakeholders, including CMOs, rightsholders, and
venues—have distinct roles and exchange various forms of value. Each stakeholder maintains control
over their own data, requiring security requirements that reflect these relationships.</p>
        <p>This leads to the development of security policies in R2.1 and R2.2, which ensure that data owners
(e.g., rightsholders, CMOs) control access to their data. For instance, a rightsholder controls who can
access their earnings and usage data, while a CMO can delegate data control to trusted agents, reflecting
the decentralized structure of the ecosystem.</p>
        <p>The value model helps ensure that security requirements consider these multi-actor relationships,
allowing for both flexibility and strong protections.</p>
        <p>Data Security for Cross-Border Transactions. The value model shows that cross-border
transactions, such as when rightsholders reside in diferent countries, involve the transfer of money
between CMOs. This introduces risks related to data privacy and security during these international
exchanges.</p>
        <p>The security requirements in Sec. 7 address these risks by enforcing encryption and anonymization
during the transfer of personal and financial data between CMOs. The value model illustrates where
data crosses national borders, ensuring that the necessary protections are in place to comply with
regulations like the General Data Protection Regulation (GDPR)2.</p>
        <p>Intellectual Property (IP) Protection and Mandates. The value model captures the
process by which rightsholders grant mandates to CMOs, allowing them to collect license fees on their
behalf. These mandates represent valuable intellectual property (IP) rights, which must be protected
against unauthorized access.</p>
        <p>The security requirements in Sec. 7, supported by R2.1, focus on protecting IP data. Unauthorized
access to this data could lead to exploitation of rightsholders’ works without proper compensation.
Therefore, security measures such as discretionary access control (DAC) and attribute-based access
control (ABAC) ensure that only authorized users can access the IP-related data.</p>
        <p>Limitations. While the value model provides a structured way to derive security requirements, it
still has some limitations as follows.</p>
        <p>• The value model focus on economic exchanges may overlook non-monetary assets or intangible
values, such as reputational risks or stakeholder trust, which could also influence security needs.
• This method assumes that all actors are clearly defined and that their economic roles and exchanges
remain stable, which may not hold true in dynamic ecosystems where new stakeholders or value
lfows could emerge over time.
• For now, the approach relies on workshops and stakeholders’ input to validate security
requirements. If certain stakeholder groups are underrepresented or not fully engaged, there is a risk
that their security concerns may not be adequately addressed, potentially leading to gaps in the
overall security framework.</p>
      </sec>
      <sec id="sec-8-2">
        <title>8.2. Evaluation: Correctness and Completeness</title>
        <p>A validation workshop with stakeholders was held to validate the proposed access control rules. During
this session, we examined and discussed each asset and its corresponding rules in order. This was done
while presenting a copy of the data model to clarify and refer to the specific assets and relations we
were discussing. As expected, there was feedback on our initial proposal which has been processed.
Aside from this feedback, however, we did not receive a further indication that specific (general) rules
were missing. Also from a reasoning standpoint, the collection of access control rules contained for
each asset and each main user/stakeholder under which general condition they would need to have
access. The combination of this reasoning and the stakeholder validation leads us to conclude that the
methods used led to a suficient degree of correctness and completeness.</p>
        <p>Since development is an iterative process, wishes and insights will likely change throughout the
project’s lifetime. This highlights the importance of keeping the stakeholders involved and iteratively
validating whether the access control rules still match their needs and expectations, even after initial
deployment. Among others, [19] also highlights this as an important aspect of security requirement
engineering in general. Also specifically for access control policy in particular, the iterative nature of
the process is highlighted in research [20].</p>
        <p>Limitations. We were not able to directly contact all stakeholder groups. Instead, we were able to
extensively elicit from a stakeholder group, namely the CMOs, that is (in theory) aware of the wishes
of most other stakeholder groups. However, this is still an important limitation to the assessment of
whether the elicited access control rules are complete and correct. This is because we could not directly
involve all the most important intended users of the system. This goes against the principle of eliciting
directly from the user, which is commonly accepted to yield better requirement results [21].</p>
      </sec>
      <sec id="sec-8-3">
        <title>8.3. Evaluation: Efectiveness and Eficiency</title>
        <p>In general, we evaluate the process to be suficiently efective and eficient. A (suficiently) complete
and correct list of general access control rules has been produced within the allotted time, with only
3 sessions with external stakeholders. During the process we experimented with diferent methods
of formatting the proposed controls/results, so in future iterations, this would likely be even more
efective.</p>
        <p>We were not able to speak to all stakeholder types directly. In the case of MUSIC360 the stakeholder
group we were able to elicit from extensively (CMOs) is in contact with all other main stakeholders. This
allowed them to provide substantiated reasoning for their wishes. Especially during the initial phase,
this had a positive efect on eficiency since we only had to set up limited interviews and/or workshops
before reaching an initial proposed set of rules. This indicates that in time- or resource-constrained
projects eliciting only from a select group of stakeholders that is knowledgeable about other groups can
at least provide the basis for the initial proposal. This does not take away that to improve validity the
results would need to be validated with the other stakeholder groups themselves. However, to reach the
initial proposal, sessions with a stakeholder group that is (at least to an extent) knowledgeable about
the wishes of the other stakeholder groups, could be suficient.</p>
        <p>Before the final validation workshop, the assets had not been validated for completeness and
correctness. Instead, we used the final validation workshop both for validating the proposed list of assets
as well as their corresponding access control rules. This led to a situation where we had missed some
resources that could be considered as assets, and in turn had not prepared the proposed access controls
for these assets. For future implementations of our methods, we would suggest validating the list of
potential assets separately from the final access control validation workshop.</p>
        <p>Limitations. Due to logistical issues, not all the researchers were able to attend the second exploratory
workshop in person. In our case, the semi-hybrid format made it harder for the online participants to
interact. While research has been done on hybrid formats for education and courses, we find a gap
regarding its efects on the requirement elicitation process in particular, which could be an angle for
future research.</p>
        <p>The workshops we held were with participants who had a relatively technical background. They
were not all computer scientists or developers but had generally worked (extensively) with technical
projects during their careers. This potentially allowed the currently chosen method of presenting the
access controls to be more well-understood by these stakeholders, than by completely non-technical
stakeholders. During this research process, we used the same tabular format for presenting the controls
to these stakeholders (with explanation) as to the developers. In the case of less technical stakeholders,
we expect that a more visual presentation method may be more suitable. Specific research into formats
and language for presenting access control rules for stakeholder validation could be an angle for future
research.</p>
      </sec>
      <sec id="sec-8-4">
        <title>8.4. Evaluation: Ease of implementation</title>
        <p>There are several aspects necessary to implement access control policies regardless of the access control
type being implemented.</p>
        <p>• Which user (types) need to access a resource?
• What access type should they have? (CRUD)
• Under which condition?</p>
        <p>The produced access control rules contain all three of these components. This in turn means that
the rules are implementable. In this case, the access rules were all Read access (except for CMO
admin/fingerprint devices/music providers), but for cases where this would difer per line, an extra
column stating the type of access could easily be added.</p>
        <p>Regarding ease of implementation in terms of clarity, we tried multiple ways of presenting the
controls. The presented format was decided upon through discussion within the team on the level of
clarity per presentation approach. The methods tried were:
• A tabular overview from the perspective of the user, for purely the identified assets. In other
words "User X can access, Resource Y under condition Z, can access A under condition B, etc".
• The same as above, for non-assets as well
• A tabular overview from the perspective of the asset (as was the final chosen presentation type),
however, presented within a single table
• A visual diagram style representation from the perspective of the asset.</p>
        <p>Based on an evaluation by the developer and team members on clarity, we decided that an overview
per asset was the preferred method.</p>
        <p>Another option would have been to provide the access control rules in code format. The benefit of
this would have been an even higher level of realizability for the eventual developer. We expect that
this could be preferred for some projects where:
• The eventually chosen access control type is (as good as) set in stone
• The language/framework that the rules will be implemented in is certain
• The requirement engineer is adept in the language/framework that the rules are to be implemented
in</p>
        <p>When these are not the case, we expect it to be more efective to provide the logical reasoning behind
access control rules as a separate document, as has been done in our results. In other words to stay
away from particular code formats. These criteria would have to be tested over a larger number of
projects to assess whether they constitute an efective rule of thumb regarding the formatting of access
control rule deliverables from the requirement engineer(s) to the development team.
Limitations. The validation for ease of implementation was limited to other people working on the
MUSIC360 project. To make truly grounded claims regarding ease of implementation for this specific
format, a higher sample size and possibly implementations over diferent projects would be needed.
In our case, the tabular format for presenting access control rules was found to be efective. However,
which exact wording patterns or structure to use has not been particularly researched. Nor can our
research provide grounded claims on whether the type of wording we used is best for enhancing ease
of implementation. We propose future research to focus specifically on best practices and conventions
regarding framing access control conditions for improving ease of implementation. Including for
example further support for which situations allow handover in code to be efective.</p>
      </sec>
    </sec>
    <sec id="sec-9">
      <title>9. Conclusion</title>
      <p>Value-based Security Requirements. In this paper, we have proposed an approach to elicit security
requirements in digital ecosystems, starting with identifying high-level goals, understanding what is at
stake by means of an e3value model, deriving a UML class model, and finally identifying asset access
rights and related access controls. We evaluated our approach in terms of correctness, completeness,
eficiency, efectiveness, and ease of implementation.</p>
      <p>Future Work. We have not covered R3 ‘Data owners can make data available in an inaccessible,
containerized way’. We plan to address this requirement with Multi-Party (MPC) computing [22] and
homomorphic computing [23]. These are techniques to do calculations without knowing the complete
data, or knowing the data at all. Also, it can be controlled by which parties can read the outcome. An
example use case is that a CMO is interested in the efect of a playlist on revenue of retail shops in The
Netherlands. However, the revenue is only known to the shop itself, and can not be shared in plain text.
However, the aggregated revenue number for all relevant shops is visible to the CMOs. There is a need
for computation of the total revenue in a sort of secure container where no one knows the inputs (the
revenue numbers of the individual shops) but where the CMOs know the aggregated results. It is clear
that it is a diferent class of security requirements than access controls only. We plan to address this
with MPC computing, most notably secret sharing [24] and homomorphic encryption.</p>
    </sec>
    <sec id="sec-10">
      <title>Acknowledgments</title>
      <p>Funded by the European Union under project no. 101094872. Views and opinions expressed are however
those of the author(s) only and do not necessarily reflect those of the European Union. Neither the
European Union nor the granting authority can be held responsible for them.
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