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  <front>
    <journal-meta>
      <journal-title-group>
        <journal-title>H. Baghcheband);</journal-title>
      </journal-title-group>
      <issn pub-type="ppub">1613-0073</issn>
    </journal-meta>
    <article-meta>
      <title-group>
        <article-title>CNP-MLDM: Contract Net Protocol for Negotiation in Machine Learning Data Market</article-title>
      </title-group>
      <contrib-group>
        <contrib contrib-type="author">
          <string-name>Hajar Baghcheband</string-name>
          <email>h.baghcheband@fe.up.pt</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Carlos Soares</string-name>
          <email>csoares@fe.up.pt</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff1">1</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Luis Paulo Reis</string-name>
          <email>lpreis@fe.up.pt</email>
          <xref ref-type="aff" rid="aff0">0</xref>
          <xref ref-type="aff" rid="aff2">2</xref>
        </contrib>
        <contrib contrib-type="author">
          <string-name>Workshop</string-name>
        </contrib>
        <contrib contrib-type="editor">
          <string-name>Machine Learning, Data Market, Negotiation, Contract Net Protocol</string-name>
        </contrib>
        <aff id="aff0">
          <label>0</label>
          <institution>FEUP - Faculty of Engineering University of Porto</institution>
          ,
          <addr-line>Porto</addr-line>
          ,
          <country country="PT">Portugal</country>
        </aff>
        <aff id="aff1">
          <label>1</label>
          <institution>Fraunhofer AICOS Portugal</institution>
          ,
          <addr-line>Porto</addr-line>
          ,
          <country country="PT">Portugal</country>
        </aff>
        <aff id="aff2">
          <label>2</label>
          <institution>LIACC-Artificial Intelligence &amp; Computer Science Laboratory(member of LASI LA)</institution>
          ,
          <addr-line>Porto</addr-line>
          ,
          <country country="PT">Portugal</country>
        </aff>
      </contrib-group>
      <volume>000</volume>
      <fpage>0</fpage>
      <lpage>0003</lpage>
      <abstract>
        <p>The Machine Learning Data Market (MLDM), which relies on multi-agent systems, necessitates robust negotiation strategies to ensure eficient and fair transactions. The Contract Net Protocol (CNP), a well-established negotiation strategy within Multi-Agent Systems (MAS), ofers a promising solution. This paper explores the integration of CNP into MLDM, proposing the CNP-MLDM model to facilitate data exchanges. Characterized by its task announcement and bidding process, CNP enhances negotiation eficiency in MLDM. This paper describes CNP tailored for MLDM, detailing the proposed protocol following experimental results.</p>
      </abstract>
    </article-meta>
  </front>
  <body>
    <sec id="sec-1">
      <title>1. Introduction</title>
      <p>
        The Machine Learning Data Market (MLDM), a data market framework based on multi-agent systems [
        <xref ref-type="bibr" rid="ref1 ref2 ref3 ref4">1,
2, 3, 4</xref>
        ], is designed to facilitate data exchange among agents to enhance their predictive performance.
Each agent initially builds a model using local training data and assigns a value to newly collected
data for potential trading. Agents then engage in negotiations to buy or sell data, setting prices based
on the data valuation methods and their respective budgets. Through these transactions, agents aim
to improve their learning models and overall performance by incorporating exchanged data. The
framework also includes mechanisms for performance evaluation after exchanging data to assess the
impact on predictive accuracy and budget.
      </p>
      <p>
        While the original negotiation strategy facilitated data exchange, it lacked eficiency. To address
this, we introduced a tailored version of the Contract Net Protocol (CNP) [
        <xref ref-type="bibr" rid="ref5">5</xref>
        ], a well-established MAS
negotiation protocol [
        <xref ref-type="bibr" rid="ref6">6</xref>
        ]. This new approach, termed CNP-MLDM, aims to optimize data exchange
processes specifically within the MLDM framework.
      </p>
    </sec>
    <sec id="sec-2">
      <title>2. CNP-MLDM</title>
      <p>In the MLDM, agents engage in dynamic data exchanges to enhance predictive modeling performance.
Seller Agents (SAs) and Buyer Agents (BAs) participate in a structured negotiation facilitated by the
CNP-MLDM protocol. Each agent develops models based on local datasets, selects traded sets, and
sets prices accordingly. Through CNP-MLDM, agents announce their intentions to sell data daily
(iteration), including the price and data valuation of the traded set(see Figure 1a). Buyers analyze
received and unexpired ofers, calculating the worth according to price and data valuation (DV)   ℎ =
( / )
∗</p>
      <p>. Buyers then rank ofers based on their worth and select the best one. If
the buyer’s budget is insuficient, it suggests a new price based on
willingToBuy and data value. After</p>
      <p>CEUR</p>
      <p>ceur-ws.org
(a) Task Announcement Message
(b) Bid Announcement Message
choosing an ofer, the buyer agent sends a response to the seller with the accepted or suggested price
and any other required information (see Figure 1b). The seller agent assesses received messages from
buyers. If a new price is suggested, the seller decides on the reduced traded data (size/quality). The
seller then sends the traded data to the buyer, who appends the new set to its training data and evaluates
model performance to measure the efect of the data exchange. If the buyer’s performance improves, it
can add the seller to a trust list for future transactions.</p>
      <p>
        The performance of the MLDM framework using the Gain-Shapley Data Value (GDSV) method
for data valuation was examined on the OpenMl-CC18 [
        <xref ref-type="bibr" rid="ref7">7</xref>
        ] (a set of classification datasets) with the
K-Nearest Neighbors (KNN) algorithm. The results compare three scenarios: GDSV, No Exchange,
and Single Agent. The GDSV scenario significantly outperforms the No Exchange scenario, with the
performance gap widening as data collection increases. The Single Agent scenario, representing the
performance with complete data access, consistently shows the highest performance. However, the GDSV
scenario approaches this maximum boundary, indicating that strategic data exchanges enable agents to
approximate the performance of a single agent collectively. Overall, the results underscore the benefits
of the MLDM framework with GDSV and Contract Net Protocol (CNP) negotiation, demonstrating that
intelligent data trading can significantly improve predictive performance( see Figure 2).
      </p>
    </sec>
    <sec id="sec-3">
      <title>3. conclusion</title>
      <p>This framework enhances the negotiation strategy in MLDM, fostering a cooperative marketplace
where agents collectively improve their learning models for better overall performance. Future work
will involve adjusting the scenario to the real world based on complex scenarios like updated prices
from buyers and the bidding mechanism for sellers, taking into account changes in the size or quality
of the traded data. Additionally, a trust list can be implemented to manage competitive relationships
among agents.</p>
    </sec>
    <sec id="sec-4">
      <title>Acknowledgments</title>
      <p>This work was financially supported (or partially financially supported) by Base Funding –
UIDB/00027/2020 of the Artificial Intelligence and Computer Science Laboratory – LIACC - funded
by national funds through the FCT/MCTES (PIDDAC) and by a PhD grant from Fundação para a
Ciência e Tecnologia (FCT), reference SFRH/BD /06064/2021 and Agenda “Center for Responsible AI’’,
nr. C645008882-00000055, investment project nr. 62, financed by the Recovery and Resilience Plan
(PRR) and by European Union -  NextGeneration EU. The computational resources of Google Cloud
Platform were provided by the project CPCA-IAC/AF/594904/2023.</p>
    </sec>
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