ELECTRONIC CONTRACT NEGOTIATION

AND RENEGOTIATION USING FEATURES

Daniel Avila Vecchiato, Maria Beatriz Felgar de Toledo

Institute of Computing, State University of Campinas, Av. Albert Einstein, 1251, Campinas, SP, Brazil

Marcelo Fantinato

School of Arts, Sciences and Humanities, University of São Paulo, R. Arlindo Béttio, 1000, São Paulo, SP, Brazil

Itana Maria de Souza Gimenes

Department of Informatics, State University of Maringá, Av. Colombo, 5.790, Maringá, PR, Brazil

Keywords: Business process management, e-Contracts, Contract negotiation/renegotiation, e-Services, Quality of

service.

Abstract: Electronic contracts (e-contracts) usually describe cross-organizational business processes defining

electronic services to be provided and consumed as well as constraints on service execution such as, for

instance, Quality of Service (QoS). Due to market dynamism, it is common that organizations involved in a

cooperation need to do some adjustments in a pre-established e-contract. These changes should be allowed

through renegotiation of contractual clauses after the e-contract is already signed and being enacted. In this

paper, feature modeling is used to represent electronic services (e-services), QoS attributes and control

operations to be applied when QoS attribute levels are not met. In addition, an execution environment is

proposed to support contract establishment, business process execution, service monitoring and contract

renegotiation.

1 INTRODUCTION

The current Business Process Management (BPM)

scenario includes: i) one or more organizations that

provide and/or consume electronic services (e-

services) using internet; ii) negotiation and

establishment of electronic contracts (e-contracts),

including quality of service (QoS) attributes and

levels; iii) definition, enactment, monitoring, and

auditing of business process; and, iv) process

analysis and optimization. The competitiveness and

increasing demand have driven organization to the

adoption of organizational models and business

processes increasingly complex and interconnected,

which requires the computational support provided

by BPMS.

E-contracts between two or more partners

interested in an inter-organizational business process

establish the activities to be performed and the

obligations, permissions and rights related to each

involved party. During contract enactment, if a party

is unable to fulfill contractual clauses, a contract

renegotiation may be triggered.

In this paper, a complete BPM infrastructure is

proposed comprising the e-contract life cycle from

negotiation, establishment and enactment to

renegotiation. The main contributions of this paper

are: i) an extension of a pre-existent feature

metamodel to include the control operations to be

performed in case of e-contract violation (Fantinato

et al., 2008); ii) an extended infrastructure to support

e-contract negotiation and renegotiation; and, iii)

more efficient management, organization and reuse

of information necessary for the establishment and

renegotiation of e-contracts.

The feature modeling technique is used for the

representation of e-services and QoS attributes.

Some advantages of this technique are (Fantinato et

al., 2008): flexibility in the use of rules for e-

services specification; modularization facilities

313

Avila Vecchiato D., Beatriz Felgar de Toledo M., Fantinato M. and Maria de Souza Gimenes I.

ELECTRONIC CONTRACT NEGOTIATION AND RENEGOTIATION USING FEATURES.

DOI: 10.5220/0002800203130318

In Proceedings of the 6th International Conference on Web Information Systems and Technology (WEBIST 2010), page

ISBN: 978-989-674-025-2

particularly for QoS attributes specification; and,

structured representation of the optional and

mandatory WS-contract elements. Taking these

concerns into account, feature modeling may also be

successful applied in the representation of control

operations for contract renegotiations.

The paper is organized as follows: Section 2

briefly discusses the basic concepts of this work; in

Section 3 some related work are presented; the

extended feature metamodel is presented in Section

4 and the BPM infrastructure approach is showed in

Section 5; Section 6 presents some lessons learned;

and, finally, Section 7 concludes the paper.

2 BACKGROUND

This section presents basic concepts related to Web

services, e-contracts, contract negotiation and

feature modeling.

2.1 Web Services

Web Services have spread as a promising

technology for the effective automation of cross-

organizational interactions (Alonso et al., 2003)

(Papazoglou, 2007). The major benefits of this

technology is the wide standardization including: a

language to describe service interfaces (Web

Services Description Language – WSDL) (W3C,

2006), a service directory structure and APIs for

service publication and discovery (Universal

Description, Discovery, and Integration – UDDI)

(OASIS, 2004) and a communication protocol

(Simple Object Access Protocol – SOAP) (W3C,

2007) for exchanging structured information in the

eXtensible Markup Language (XML) (W3C, 2008).

2.2 e-Contracts

It is common to find organizations that are acting in

a cooperative way to reach business objectives

through the implementation of cross-organizational

processes. The organizations interested in internet

business partnerships must define details of the

business process to be enacted. This could be done

with e-contracts (Fantinato et al., 2008). An e-

contract defines details about the collaborative

organizations, the activities to be executed and the

contractual clauses that must be met during process

enactment (Grefen et al., 2001).

The clauses could be of three distinct types:

obligations, rights and prohibitions (Fantinato et al.,

2008). The obligation clauses include QoS of e-

services within the inter-organizational process. In

addition to the functional aspect of e-contracts, there

is also the legal aspect that will not be considered is

this paper.

2.3 Contract (Re)Negotiation

The negotiation process consists in agreeing about

structure and properties of the contract model, as

well as property values (Bacarin et al., 2008). These

properties and values can be predefined in the

model, negotiated or even set during contract

enactment. In the latter case, a range of values must

have been previously agreed.

The e-contract establishment has to aggregate

some process value to the involved organizations.

Contract negotiation requires offers and counter-

offers between partners disposed to collaborate

(Hanson and Milosevic, 2003). This process can be

initiated by either sides, the receiving part interprets

the offer and may refuse, agree or generate a counter

proposal (Angelov and Grefen, 2008b).

Negotiation can include aspects about the model,

clauses and variable values. Many protocols have

been proposed to achieve automatic contracting

establishment such as bargain, auction and ballot

(Bacarin et al., 2008).

Renegotiation may be used when some

contractual clauses are broken or when changes in

the business process are required. Instead of

applying renegotiation, other possible alternatives

are: termination and/or rollback of the process and

judicial dispute. This paper mainly addresses

renegotiation.

2.4 Feature Modeling

Feature modeling captures and manages common

points and variabilities in software product lines

(Czarnecki et al., 2005). A feature model represents

properties of some entity of interest. It can denote

any functional or non-functional property in the

requirement, architectural or other level. Features

can be mandatory, optional or alternative. They are

organized into a tree-like diagram in which a node

represents a feature and each feature can be

described by a set of sub-features represented as

descendant nodes.

A feature model describes a system family. A

family member can be configured by selecting the

desired characteristics from the feature model within

the variability limits of the model. This process is

called feature model configuration.

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3 RELATED WORK

The CrossFlow project is pioneer in the area of

cross-organizational business process (Grefen et al.,

2001). Like some other earlier works, they use

metamodels to facilitate e-contract establishment.

More recently, Angelov and Grefen (2008b)

defined an e-contract metamodel with different

perspectives. The function perspective supports

designers in the specification of contract activities.

The communication perspective supports

information exchange between parties and defines

restrictions in activities execution. The negotiation

activities are part of the communication perspective.

Bacarin et al. (2008) put forth a negotiation

protocol with some primitive actions to assign

property values, to send offers, request for proposal

(RFP) and votes. They identify the following phases:

negotiation announcement, leader determination,

objective announcement, negotiation setup,

restriction announcement, core negotiation, commit

attempt, contract (re)construction.

Angelov and Grefen (2008a) define a reference

architecture to contract systems development, using

a component-based approach. This architecture

provides a component for each phase of electronic

contracting (information, pre-contracting,

contracting and enactment).

Hanson and Milosevic (2003) propose a

negotiation model that can be applied at different

levels: contract model, clauses and variables. During

negotiation, the contractual clauses can be modified

using insertions, updates or deletions. Values can

also be assigned to variables. The renegotiation

process is similar, but only clauses or variables can

be reassigned.

Some works use e-contract templates to facilitate

the reuse of previously established e-contracts

(Angelov and Grefen, 2008b) (Bacarin et al., 2008)

(Grefen et al., 2001) (Hanson and Milosevic, 2003).

Feature models are used in the present work to

generate the e-contract template and manage the

obligations, permissions and prohibitions of each

part. They facilitate e-contract information

organization and reuse through the use of common

and variable points.

In a general way, the renegotiation issue is still

not completely addressed in a proper way. Some

architectures and frameworks allow contract update

during process execution (Angelov and Grefen,

2008a) (Bacarin et al., 2008). However, none of

them specifies the actions to be performed in the

case of contract violation. The proposed framework

addresses this issue.

4 FEATURE METAMODEL

The BPM context involves providers and consumers

of e-services that can be composed into a business

process. This collaboration must be regulated by an

e-contract between the involved parties. In the

proposed infrastructure, the e-services are

implemented as Web Services and the e-contract is

called WS-Contract (E-Contract for Web Services)

according to the metamodel presented in Figure 1

(Fantinato et al., 2008). A WS-Contract is composed

of: parties, e-services, contractual clauses and a

business process.

Figure 1: WS-Contract Meta model.

WS-BPEL (Web Services Business Process

Execution Language) (OASIS, 2007) is used to

define the involved parties and the orchestration of

the e-services within the inter-organizational

process. E-services and QoS attributes are described

in WSDL and WS-Agreement (OGF, 2007)

respectively. A complete view of the WS-Contract

Metamodel can be seen in (Fantinato et al., 2008).

Since different e-contracts can be reused between

different cooperation opportunities, a useful strategy

explored in this approach is using contract

templates. E-contracts templates are defined only

once, and different – but similar – contract instances

can be created. To facilitate the creation of e-

contract templates, this approach uses feature

models that are used to represent in a high level of

abstraction the information to be provided by the

involved organizations and which will be used in

such templates.

The feature metamodel for e-contracts has been

proposed by Fantinato et al. (2008). It originally

consisted of two sub-trees, e-services and QoS-

attributes, but it has been extended to include a

Control-operations sub-tree. The feature diagram

structure and sub-trees are shown in Figure 2. Each

sub-tree is described as follows:

 e-Services Sub-tree: this root feature is

mandatory. It contains features representing

the e-services offered by an involved

organization;

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315

Figure 2: Feature Metamodel for E-services, QoS and Control Operations.

 QoS-attributes Sub-tree: this root feature is

optional. It contains features that represent the

QoS attributes. These attributes are attached to

e-services defined into the E-Services sub-

tree. It includes choices of QoS attribute

levels;

 Control-operations Sub-tree: this root feature

is optional. It specifies control operations to

be executed when QoS attribute levels are not

met. Some of the control operations may be:

Contract Renegotiation of clause, variable or

price, Process Terminate, Process Rollback,

Process Suspend, Administrator/User

Notification or Penalty Application.

The control operation sub-tree can be associated

directly to an e-service or to specific QoS attributes

of the e-service. The former case is used as a default

option whereas the latter case is used as a

specialization option. When a QoS attribute is not

met, if there are control operations settings defined

specifically for it, they are triggered to answer its

non-fulfillment; otherwise, it is verified if there are

control operations settings defined generically for

the associated e-service which should be triggered.

With this feature structure support, a unique set

of control operations options, defined only once, can

be reused by all the QoS attributes and levels

associated to all the e-services. During feature model

configuration, specific control operations options

can be selected for each QoS attribute or for each e-

service.

When the Contract Renegotiation operation is

chosen, a negotiation protocol must be specified. It

will be performed after a notification is sent by the

monitor to the collaborating parties. Other

operations such as Process Terminate, Process

Rollback and Process Suspend will be executed by

the WS-BPEL server. The monitor and WS-BPEL

server are elements of the proposed infrastructure

described in section 5.

Figure 3 presents an example of a feature model

configuration elaborated through the feature model

plug-in (Antkiewicz and Czarnecki, 2004). This

example is related to flight services provided by an

airline company to a travel agency.

Figure 3: Flight Services Example.

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The control-operations sub-tree is associated to

the e-service flight-purchase and its QoS attributes

availability and reply-time. The renegotiation of

price is defined as the default control operation for

the flight-purchase service, which must be triggered

if any QoS attribute – for which there is no

specialized control operation – is not met.

Specifically for the availability attribute, there is a

control operation specialization: if this attribute is

not met, the business process must be terminated.

5 BPM INFRASTRUCTURE

The proposed BPM infrastructure is shown in Figure

5. It comprises four organizations: consumer,

supplier, negotiator and monitor. The Consumer

Organization include: i) a structure called WS-

Contract Definition responsible for negotiation and

establishment of WS-Contracts based on features; ii)

a structure WS-Contract Execution responsible for

the business process execution; and, iii) a SOC

System necessary if the consumer services are part

of the business process to be executed. In the

Provider Organization, the SOC System control

the Web Services subcontracted by the consumer.

The Monitor Organization has one structure WS-

Contract Monitoring that follows the business

process execution using a set of web services

monitors. The monitors use the QoS terms contained

in the WS-contract for service monitoring. The

Negotiator Organization has one structure WS-

Contract Negotiation that uses a set of predefined

protocols responsible to negotiation/renegotiation of

contracts between providers and consumers

To establish cooperation (Figure 4), a negotiation

is initiated between the Consumer and Provider

generating the feature model diagram (1) and the

WS-contract defined according to those feature

models and their respective feature model

configurations (2). Contract parts are sent to the

interested organizations (3 and 4). The WS-BPEL

server interprets the business process (5), and

invokes local (6) or contracted (7) Web Services. If

monitoring is specified, the monitor organization is

notified (8) and QoS terms, represented by WS-

Agreement, in the WS-contract are identified (9).

The monitor services will follow the invoked

services execution to ensure that the contracted QoS

levels are met (10 and 11). If any contracted term is

not satisfied, the control operation, as specified in

the contract, is performed. For negotiation/

renegotiation (12), the WS-Contract Negotiation

uses a set of predefined protocols (13), if the

contract has to be finalized the WS-BPEL server is

informed to stop the enactment (14).

Figure 4: The Proposed Infrastructure.

Some prototypes have already been developed to

support this infrastructure. For the WS-Contract

Definition, the FeatureContract toolkit (Fantinato et

al., 2008) uses the feature plug-in (Antkiewicz and

Czarnecki, 2004) – a tool developed by other

research group. The Negotiator Organization support

tool is being treated inside the scope of this work.

Moreover, another work is dealing with the WS-

Contract Monitor tool.

6 LESSONS LEARNED

The use of feature models during the renegotiation

of e-contracts makes this process easier to

understand, simple and systematic. The approach

improves information and artifact reuse. Common

points and variabilities provided by feature modeling

represent control operations, triggerable in case of

contract violation, in a controlled and structured

way. As well as in the original approach (Fantinato

et al., 2008) which was extended here, distinct

stakeholders, at different levels, can benefit from the

proposed approach.

However, some disadvantages or limitations of

the approach can be pointed out: i) necessity of

ELECTRONIC CONTRACT NEGOTIATION AND RENEGOTIATION USING FEATURES

317

knowledge about the feature modeling technique; ii)

lack of direct support for agreements between more

than two parties; and, iii) negotiation is made in an

offline way; negotiation protocols have not yet been

included to automatically perform negotiation.

7 CONCLUSIONS AND FUTURE

WORK

This paper has presented an infrastructure that

supports e-contract negotiation, establishment,

enactment and renegotiation. More specifically, the

approach advantages are: i) more efficient

information management, organization and reuse

that is necessary for the negotiation and

renegotiation of e-contracts; ii) better understanding

of the renegotiation process through identifying all

possible alternatives to dynamically adjust the e-

contract; and, iii) better information organization

and presentation of e-services and QoS attributes

linked with control operations using feature

modeling.

Future works, besides focusing on the

weaknesses cited in Section 6, include: full

implementation of the WS-Contract Negotiation

element with some example protocols; extension of

the WS-Contract metamodel to include the control

operations elements already supported by the feature

models; and integration with the WS-Contract

monitoring tool which has been developed by the

same research group.

ACKNOWLEDGEMENTS

This work was supported by The State of São Paulo

Research Foundation (FAPESP) and The National

Council for Scientific and Technological

Development (CNPq), Brazil.

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