=Paper=
{{Paper
|id=Vol-161/paper-2
|storemode=property
|title=A Semantic Marketplace of Peers Hosting Negotiating Intelligent Agents
|pdfUrl=https://ceur-ws.org/Vol-161/FORUM_01.pdf
|volume=Vol-161
|dblpUrl=https://dblp.org/rec/conf/caise/PatkosP05
}}
==A Semantic Marketplace of Peers Hosting Negotiating Intelligent Agents==
https://ceur-ws.org/Vol-161/FORUM_01.pdf
3
A Semantic Marketplace of Peers Hosting Negotiating
Intelligent Agents
Theodore Patkos and Dimitris Plexousakis
Institute of Computer Science, FO.R.T.H.
Vassilika Vouton, P.O. Box 1385, GR 71110
Heraklion, Greece
{patkos, dp}@ics.forth.gr
Fax Number: (+30) 2810391638
Abstract. Achieving interoperability and automation in job execution is of
utmost importance in the current economic trading sphere. This paper proposes
a design that integrates three prominent technologies for improving next-
generation e-Commerce applications; autonomous software agents, peer-to-
peer networking and the Semantic Web. SeMPHoNIA is an architecture for an
agent-based marketplace, utilizing knowledge from RDF product repositories,
in an open peer-to-peer environment. The platform defines the basic stages of
the process of e-trading, facilitating users in closing deals in an automated
manner. The implementation of our approach is demonstrated in the context of
auction scenarios.
1 Introduction
The emergence and rapid development of electronic commerce has influenced many
fields of human activity and business industry, providing a “gravity well”, which
pulls a variety of diverse technologies and novel research efforts into closer
collaboration. Recent years have seen an enormous increase in the role of
information technology in markets, in particular the emergence of electronic
marketplaces [2]. The current economic trading sphere is structured on top of an
open, distributed, heterogeneous and, most often, unreliable environment.
Human participants are still actively involved in all stages of the buying process.
As the trend of e-Commerce continues though, an inevitable growth in the number
and features of on-line markets is observed, causing the task of monitoring and
effective decision-making to become trivial and time-consuming for humans. The
increasing degree of heterogeneity and sophistication on both the business and the
customer side will render interoperability and automation in execution the most
challenging tasks that next generation e-Commerce applications will face.
In this paper we introduce the design and implementation of a system, called
SeMPHoNIA (Semantic Marketplace of Peers Hosting Negotiating Intelligent
Agents), for addressing issues of current e-trading. The system integrates and
exploits three enabling technologies, namely intelligent software agents, peer-to-peer
systems and the Semantic Web, into a unified platform. It is an architecture for an
Proceedings of the CAiSE'05 Forum - O. Belo, J. Eder, J. Falcão e Cunha, O. Pastor (Eds.)
© Faculdade de Engenharia da Universidade do Porto, Portugal 2005 - ISBN 972-752-078-2
4 Patkos Theodore, Plexousakis Dimitris
agent-based virtual marketplace structured on top of a peer-to-peer network, utilizing
semantic approaches. SeMPHoNIA could be considered as what [4] describes as the
third key actor in agent-mediated e-Commerce applications, apart from buyers and
sellers: the “market owner”, an environment that sets and controls the rules, in which
buyers and sellers trade. The implementation of our approach is demonstrated in the
context of auction scenarios, intending to facilitate users in discovering and bidding
across multiple interrelated auctions with varying start and end times and protocols.
Still, auction scenarios are just a paradigm of multi-agent negotiation. The platform
is designed to be extensible at various levels, intending to encourage experimentation
with aspects of domains that go beyond auction theory.
2 SeMPHoNIA Platform Architecture
The SeMPHoNIA platform models aspects of market mechanisms that represent a
common interaction medium for users on the Internet. It integrates three existing
technologies; JXTA [6] for configuring the peer-to-peer network, Grasshopper [3]
for managing the multi-agent character of the system and ICS-FORTH RDFSuite [5]
for exploiting technologies of the Semantic Web. The JXTA Engine module is
responsible for implementing JXTA protocols to allow the application to function as
a peer, collaborate with other peers and deploy peer-to-peer services. The
Grasshopper Middleware module is the component that undertakes the role of
automating the negotiation procedure by creating, controlling and monitoring
software agents that represent human users. Finally, the Semantic Search Engine
module facilitates semantic publish and discovery of products on the network,
exploiting software tools provided by the ICS-FORTH RDFSuite, such as RDF
validation, storage and querying [1]. At the highest layer, the user interface is
defined, displaying information about the progress of a user’s auctions.
Three layers of functionality synthesize the platform’s behavior; its semantic, its
multi-agent and its peer-to-peer character. Before going into details regarding the
platform as a whole, we elaborate on the different layers and their role in the system.
2.1 Semantic Character
Traditional Web-based product searching based on keywords appears to be
insufficient and inefficient in the ‘sea’ of information [7]. Especially in e-auction
sites, the current trend of searching catalogues of available products is a rigorous
procedure. Instead, next generation e-markets should be able to handle customer
queries, such as “Find all running English auctions of paintings created by
impressionists of the 16th century”. Ontologies have shown to be the right answer to
knowledge structuring.
For that purpose, in SeMPHoNIA project we have developed two types of
ontologies; process ontologies, which are specifically about auction-related concepts
and attributes, and domain ontologies, which enrich product descriptions with
metadata to accurately describe their features.
5
Until now, systems based on centralized ontology schemes suffer from difficulties
concerning development and maintenance [8]. The SeMPHoNIA infrastructure, on
the other hand, takes advantage of local ontologies, allowing participants to build
and maintain their own RDF knowledge databases for describing products for sale.
More specifically, each item auctioned is related to a specific domain. A retailer
describes metadata about products in the corresponding domain ontology of that
product. The auction ontology captures the characteristics of a particular auction
session combining knowledge from auction protocols and other common trading
concepts to specify the context, in which the system operates. This ontology type is
used to model all information needed for an auctioneer to initiate a new auction
session and for a customer to determine a desired session based on criteria, such as
the broker’s identity, payment accepted etc.
2.2 Peer-to-Peer Character
SeMPHoNIA’s peer-to-peer network is an asynchronous-message-passing super-
peer system that implements the auction marketplace environment. The peer-to-peer
network structure harnesses the computing power of capable peers (resource sharing)
and impels efficient ontology distribution across nodes (knowledge sharing).
Three are the basic types of SeMPHoNIA peers: customer, auctioneer and
operator peers. Customer and auctioneer peers serve as individual end users. The
latter have the additional functionality of making ontologies available on the
network. Therefore, they are always accompanied by an ontology database,
describing the selling products, along with the corresponding RDFServer, which acts
as a mediator between the database and the network. The third type of peer is the
operator peer that acts as a super-peer and provides zero or more agencies to the
platform. Agencies are places, where software agents can exist and interact. Simple
peers connect with operator peers to ensure greater reliability and scalability. Thus,
they supply the medium, where all auction operations take place. Operator peers
interconnect forming a backbone of peer clusters, bridging remote clusters and
permitting the application of message propagation algorithms to the underlying peers
of each cluster, avoiding message flooding to the entire network.
SeMPHoNIA peers advertise their services in language-neutral metadata
structures, represented as XML documents, called advertisements. An advertisement
is the basic unit of data exchanged between peers that provide information about
available resources. All peers contribute to increasing the level of connectivity to the
overall network, by caching locally XML advertisements and automatically
delivering them to interested peers upon request, without any need for human
intervention. Another important notion of the SeMPHoNIA peer-to-peer network
architecture is the peer-grouping concept. Peer groups promote trusted services by
segmenting the network space into distinct communities of peers. In SeMPHoNIA,
for every auction listed on the network a new peer group is created by the auctioneer
peer. Whenever a customer decides to participate in an auction, it must first join the
corresponding auction peer group and, only after the admission is granted, the peer is
allowed to send its agents to the auction place. A variety of authentication
mechanisms and trust models for allowing peer group registration can be applied.
6 Patkos Theodore, Plexousakis Dimitris
2.3 Multi-agent Character
Agent technology represents a flexible way of conceptualizing and implementing e-
Commerce transactions. Agents in SeMPHoNIA are used to facilitate the connection
of buyers and sellers and to automate the process of negotiation at the context of
auction scenarios. Users may decide to participate in multiple auctions at the same
time, when the result of one auction may affect the action taken for the other. Agents
automate bidding actions and make inferences to determine the optimum path, when
interrelated auctions are involved, based on the human user’s preferences and on
their internal knowledge. The platform currently supports three types of auctions;
English, Vickrey and a hybrid Peer-to-Peer auction.
We identify three types of agents operating in the SeMPHoNIA platform: A-, C-
and CL-agents. The A-agent is the auctioneer’s representative in the SeMPHoNIA
network. It coordinates the execution of a specific auction and is responsible for the
enforcement of rules governing the negotiation among all involved parties. The A-
agent is aware of its owner’s preferences, such as the type, the reserve price, etc.
This information is captured in the product’s domain ontology that the user publishes
on the network.
Customers in SeMPHoNIA may initiate one or more auction sessions,
participating concurrently in one or more auctions in each of them. Each session has
one coordinator agent, the C-agent, whose role is to manage the distinct sub-tasks
that a session is decomposed into. The C-agent controls the allocation of bids across
auctions, relying on information about their progress and on its internal strategy for
pursuing its objectives, but does not participate in any of them directly.
CL-agents are the actual participants in auctions conducted in the SeMPHoNIA
marketplace. These agents are created by the C-agent inheriting the initial knowledge
concerning their user’s preferences, i.e., the maximum price they are allowed to
spend for an item, the number of items they should intent to acquire etc. They react
to notifications sent by both the A-agent, informing them about the progress of the
auction they participate in, and the C-agent, instructing them to continue bidding or
postpone their execution, in case this serves best the session’s evolution. CL-agents
are specialized according to the type of the auction that has been assigned to them
(English/Vickrey CL-agent etc.) and the bidding strategy that the user intents to
follow (aggressive, greedy, last-minute bidding etc.). They all possess the primal
attributes and knowledge of their C-agent, but present specializations in their
behavior, justifying their characterization as clones of the C-agent.
An important aspect of the multi-agent layer of the system is that it takes
advantage of the mobility features of agents for enhancing its performance; CL-
agents migrate to place, where the auction is conducted to communicate locally with
the A-agent, eliminating possible delays due to network traffic. A C-agent may have
multiple clones scattered across different agencies on different operator peers.
2.4 The SeMPHoNIA Platform
7
Fig. 1. SeMPHoNIA platform elements, relations and interactions
The previously described characters of the system are integrated in the SeMPHoNIA
platform to implement a complete and well-defined e-trading environment. This
section presents how the different layers of functionality co-exist and collaborate.
Figure 1 displays a snapshot of the system’s state at a random moment. The
middle part shows a fraction of the peer-to-peer network. Simple peers connect with
operator peers, which in turn interconnect with each other to form a network of main
channels. Advertisements travel between peers on the same cluster or between
operator peers and are cached locally at various nodes throughout their path. These
advertisements may describe various resources, such as product domains, ontologies,
auction peer groups, agency addresses or simply the presence of peers. The lower
part of the image depicts the correspondence between auctioneer peers and their own
auction peer groups. Auctioneers may create multiple peer groups, one for every
auction they conduct. This layer also shows the virtual presence of customer peers in
each peer groups. Last, the upper part displays the multi-agent layer of the system,
which is the component that implements all auction sessions. The dashed lines imply
the relation between an operator peer and the agencies it offers. The other peers
create places for supporting negotiations and agents that travel between agencies.
3 Advanced Features
SeMPHoNIA is a multi-purpose virtual market architecture that includes numerous
advanced features for supporting human users in accomplishing electronic
negotiation tasks. One of these is the statistical information support, that is absent in
most current on-line auction sites. A special kind of agent, the Statistical Agent,
automates the process of monitoring multiple auctions by sending clone agents,
8 Patkos Theodore, Plexousakis Dimitris
while at the same time it records the history of bidding and analyzes statistical data,
such as average winning bids, price convergence behavior, equilibrium price etc.
Moreover, the design of SeMPHoNIA’s agent architecture offers flexibility and
extensibility. Application developers can manipulate CL-agents as “black boxes” and
utilize different CL-agents, that integrate various strategies, to enhance their
interaction with the system, without any need to re-design the entire negotiation
template. As a proof of concept we have created a hybrid peer-to-peer auction that
required as sole modification the enrichment of the auction ontology with the
features of this auction to allow A-agents to recognize and manage it appropriately.
In addition, emphasis has been given in designing the platform to support human
involvement in sophisticated tasks and to sustain operations in an autonomous
manner, even when the user is not connected on the network. Autonomy is promoted
at different levels of abstraction, both at the peer-to-peer and at the agent layer (i.e.,
advertisement caching, controlled message propagation, inter-agency migration etc.).
4 Conclusions
We have briefly presented the design and implementation of the SeMPHoNIA
system that integrates three emerging technologies; intelligent software agents, peer-
to-peer networking and the Semantic Web. Our primary motivation in creating this
platform has been to demonstrate the power of combining these three technologies in
facilitating the participation of users in next-generation e-Commerce transactions.
The system realizes a number of auction scenarios as a general negotiation
framework, while maintaining a flexible design that allows it to be easily extended
with new scenarios and techniques.
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