Ismaeel, Ahmad - Enabling Negotiation Between Agents and.pdf - Psychologia - koni86

Enabling Negotiation Between Agents and

Semantic Web Services

Saira Parvez Khan Sana Ismaeel 1 ,H.FarooqAhmad 2 , Hiroki Suguri 2 ,

and Muhammad Akbar Asim Elahi 3

National University of Sciences and Technology College of Signals, Pakistan

sairaparvez_se@yahoo.com

Communication Technologies 2-15-28 Omachi, Aoba-ku, Sendai, 980-0804 Japan

{farooq,suguri}@comtec.co.jp

National University of Sciences and Technology College of Signals, Pakistan

asimelahi@mcs.edu.pk

Summary. Emerging Web services standards enable the development of large-scale

applications in open environments. In particular, they enable services to be dynamically

discovered and invoked. Our research objective is to propose new paradigms for inter-

actions among semantic web services and software agents for problem solving. Agents

are autonomous entities capable of acting on behalf of their user while Semantic Web

services oﬀer a new potential of automation in e-Work and e-Commerce, where fully

open and ﬂexible cooperation can be achieved on-the-ﬂy. We believe that real goal of

semantic web can only be realized if the semantic content associated with it can be

read and interpreted. Since agent infrastructure has well-established reasoning, decision

making and interaction mechanisms, it can contribute exceptionally in this regard. In

this paper, we discuss the issue of negotiation between agents and semantic web ser-

vices and propose architecture that enables negotiation between these heterogeneous

entities.

1 Introduction

The aim of the web services (WS) endeavor is to obtain an environment where

service customers and service providers can set (negotiate) the terms and con-

ditions of service invocation automatically and then execute the necessary

actions according to the prevailing contract. The semantic web adds machine-

understandable semantics to data, thus enabling processing on behalf of the

human user. Although the new possibilities promised by emerging technologies

seem attractive, the Semantic Web with its tools and related technologies like

OWL, WSDL, UDDI, SOAP and WS are likely to fall short of realizing an auto-

mated interaction and negotiation mechanism [Jennings, 2001]. Many challenges

as stated in [20] lie ahead. That is to say, although the Semantic Web promises

to make available to programs the meaning of the content of Web pages, these

entities alone will not be able to make decisions, interact, and cooperate with

other entities. Agent infrastructure, on the other hand has much to oﬀer in this

regard. An agent possesses the ability to comprehend and interact with its en-

vironment. Because of being context-aware, autonomous and able to interpret

K.M. Wegrzyn-Wolska and P.S. Szczepaniak (Eds.): Adv. in Intel. Web, ASC 43, pp. 284– 291, 2007.

springerlink.com

Springer-Verlag Berlin Heidelberg 2007

Enabling Negotiation Between Agents and Semantic Web Services

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semantics with the help of ontological knowledge representation, agents are a

necessary complement to web services to realize the vision of semantic web. Sev-

eral arguments have been made to support the idea of integration of WS and

agent infrastructure, including [13,14,20] but perhaps none more evocative than

statements made in [21] which clearly expresses the notion that, ”software agents

are the running programs that drive WS - both to implement them and to access

them as computational resources that act on behalf of a person or organization”.

To enable this integration, several core issues are there out of which bidirectional

service discovery, service invocation and negotiation are the most pertinent. Our

goal is to take the ﬂexible interaction schemes from the Multi- Agent Systems

(MAS) research, and utilize them to enable negotiation among semantic WS, a

paradigm that supports rigid and mechanical interaction protocols, and agent

infrastructure. In this paper, we propose an abstract architecture for conducting

such negotiations. Fig 1 illustrates our vision of an autonomous, ﬂexible and

interactive environment.

Fig. 1. Block diagrammatic view of an autonomous, ﬂexible and interactive

environment

The rest of the paper is organized as follows: Section 2 brieﬂy deﬁnes the

negotiation process in the light of literature. Role of ontologies in interaction

among agents as well as WS has been highlighted in section 3. Section 4 contains

a thorough literature review concerning some highly signiﬁcant issues regarding

interoperability of the two paradigms, particularly negotiation, conversation and

interaction patterns among the two entities. Section 5 gives the details of the

proposed architecture along with UML sequence diagrams for clarity. Section 6

highlights intended future work.

2 Negotiation Process

Negotiation is an iterative communication and decision making process between

two or more agents (parties or their representatives) [4] who: (i) cannot achieve

their objectives through unilateral actions; (ii) exchange information comprising

oﬀers, counter-oﬀers and arguments; (iii) deal with interdependent tasks; and

(iv) search for a consensus which is a compromise decision. In this paper, we

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focus on introducing intelligent interaction patterns between agents and WS

aimed at utilizing the semantics associated with the involved parties. In order

to achieve this objective, the existence of a common vocabulary (i.e. ontology)

is inevitable.

3 Role of Ontologies in Interaction

3.1 Multi Agent Systems

As autonomous problem solvers, agents need to develop model of their environ-

ment that allows them to reason on how their actions aﬀect their environment

and how those changes lead them to achieve their goals [5]. Ontologies provide

the conceptual framework that allows agents to construct such models: ontologies

describe the properties of entities that agents encounter, and relations between

them. Thus a common vocabulary in the form of ontologies is at the heart of

intelligent communication among agents.

3.2 Semantic WS

The semantic web initiative [20, 21] that addresses the problem of XML’s lack of

semantics by creating a set of XML based languages, also relies on ontologies that

explicitly specify the content of the tags. The Web Ontology Language (OWL)

is a forthcoming W3C speciﬁcation for such a language which will supersede

the earlier DARPA Agent Markup language (DAML+OIL) [22]. OWL is an

extension to XML and the Resource Description Framework (RDF) enabling the

creation of ontologies for any domain and the instantiation of these ontologies

in the description of resources. The OWL-Services language (OWL-S) [19] is a

set of language features arranged in these ontologies to establish a framework

within which the WS may be described in the semantic web context.

4 Literature Review

Keeping in mind our long- term objectives, we have conducted a thorough study

of the capabilities of OWL-S and the potential of semantic web services [17,18].

With OWL-S markup of services, the information necessary for WS discovery

could be speciﬁed as computer-interpretable semantic markup at the service

Web sites, and a service registry or ontology-enhanced search engine could be

used to locate the services automatically [7,15]. Execution of a Web service can

be thought of as a collection of remote procedure calls. OWL-S markup of WS

provides a declarative, computer-interpretable API that enables automated WS

execution [7,11,19]. Given a high-level description of the task by the user, auto-

mated composition and interoperation of WS to perform the task is of particular

interest to us. With OWL-S, the information necessary to select and compose

services would be encoded at the service Web sites [3]. Software agents can be

written to manipulate and interpret this markup, together with a speciﬁcation of

Enabling Negotiation Between Agents and Semantic Web Services

287

the task and thus can be bestowed with the ability to perform the task automat-

ically [7,9,10,11]. [6] combines two recent WS languages, WS-Conversation Lan-

guage (WSCL) and WS-Agreement to implement Contract Net Protocol (CNP)

for negotiation among WS. Yet, the ﬂexibility of negotiation is far-oﬀ from that

prevalent in the agent infrastructure. FIPA [23] provides detail speciﬁcations of

Request protocol, Request/ Response protocol, CNP, English Auction, Dutch

Auction, Brokering protocol, etc. An exhaustive overview of MAS is beyond the

scope of this paper, but essential pointers include [16] and [12]. [7] presents two

signiﬁcant alternatives in empowering WS with agents’ properties. One is to im-

plement a wrapper, which turns a current Web service into an agent-like entity.

The other alternative is to capture all the functionalities of a Web Service and

imbed them into an existing software agent. [2] proposes an architectural model

for enabling transparent, automatic connectivity between WS and agent services.

A later version of this project [1] uses OWL-S to add semantic aspect to service

descriptions. [8] illustrates use of OWL as a content language for ACL messages

in MAS and conducts auctions among agents that use OWL ontologies. In this

paper, we contend that the degree of ﬂexibility that persists in agent interaction

scenarios can never be achieved in negotiations among WS alone. In order to

improve ﬂexibility level, negotiation among semantic WS and agents is highly

signiﬁcant.

5 Proposed Architecture

5.1 Assumptions

The following assumptions have been made when designing the proposed ar-

chitecture: (i) All agents are assumed to be FIPA compliant and capable of

communicating with FIPA-ACL encoded messages. (ii) All WS operate using

the standard WS stack consisting of WSDL for service descriptions, SOAP for

message encoding and UDDI for directory services. (iii) Each web service makes

use of OWL-S and exposes its domain ontologies written in OWL, a machine

readable form. (iv) The decision engine and a mechanism of web service discov-

ery and invocation from agent infrastructure is assumed to exist. (v) The FIPA

speciﬁcation for CNP as given in ﬁg 2 is followed.

5.2 Major Modules

In order to provide a proof of concept of negotiation between agents and semantic

web services, we choose one of the FIPA standard interaction protocols for the

agent infrastructure i.e. CNP [23].

According to our proposed architecture as shown in ﬁg 3, an entity called

”Ontology Gateway” (OG) acts as a broker to conduct the negotiation between

the two heterogeneous entities. Development of this gateway is underway at

NUST- Comtec lab. It is an application (neither an agent nor a web service)

that operates in a distributed environment. In its preliminary stage, the gateway

currently has ”Bidirectional OWL-FIPA Translator”. We propose another module

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Fig. 2. FIPA Contract Net

Interaction Protocol

Fig. 3. Proposed architecture of

the Ontology Gateway

called ”Negotiation Module” (NM) in the OG which supervises the sequence

of messages as they are being exchanged. This would ensure that pre-agreed

protocol is followed and whole process appear transparent to the parties involved

in the negotiation. There are several prerequisite tasks that need to be done

before carrying out the standard CNP. In our architecture, we propose a ”Control

Unit” (CU) for handling these initial tasks. Once these have taken place, the

control is shifted to the NM within the OG which then carries out the negotiation

protocol by communicating messages in a sequence. Current implementation of

the Gateway consists only of the bidirectional OWL- FIPA ontology translator.

CU has been added so as to supervise the ﬂow of messages from input to internal

architecture of the gateway as well as of messages from internal architecture to

the output.

This paper discusses only the scenario where an agent asks to conduct negoti-

ation with a semantic web service and not vice versa. Fig3 explains the proposed

architecture of an OG in detail while showing its relation with outside world,

too.

5.3 Detailed Role of Each Module in Ontology Gateway

Control Unit. First of all, the requesting agent who wants to initiate negotia-

tion invokes the service exposed by OG and sends its reference and message. This

message is received by the CU within the OG. The message content contains the

description of the service based on which CU identiﬁes other negotiating party

(i.e. a semantic web service). This is done with the help of a matchmaking ser-

vice that returns a reference or handle of that service to the CU. This handle

enables the CU fetch the service proﬁle of the service and its ontology, without

which semantic understanding is unattainable.

Bi-directional OWL- FIPA Ontology Translator. Since this ontology is

written in OWL for a semantic web service, which though is allowed as a valid

content language by FIPA but is not as expressive as SL, so there is a need to

translate this ontology from OWL to SL. The CU feeds this ontology to the

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