384
A Context-Based and Policy-Driven Method to Design and Develop Composite Web Services
step is to satisfy the needs of bodies that have
interests and/or obligations in strengthening or
restricting the execution of Web services on top
of their resources. For instance, a Web service
does not obtain the necessary authorizations to
operate on a resource since this Web service does
not comply with this resource’s requirements such
as permitted execution-time. CP4WS manages the
deployment of Web services on resources with
policies. For standardization purposes with the
policies associated with Web services’ behaviors,
WSPL is also adopted to specify deployment
policies.
Deployment Policy for
Permission.
It is about a Web service that receives the neces-
sary execution authorizations from a resource.
These authorizations are based on the state of
the resource, which manifests itself using its R-
context. The following illustrates a deployment
policy for permission in WSPL. It states that a
resource accepts the execution request of a Web
service subject to evaluating <Condition> to true.
This condition refers to some arguments like
number of active component Web services (line
07) that the resource supports their execution
and next acceptance of the resource to additional
component Web services (line 12). In the policy,
<TrueConclusion> (line 17) shows the permission

of execution, whereas <FalseConclusion> (line 20)
shows the contrary. In case of positive permis-
sion of execution, yes-permission-deployment
procedure is executed (line 18), which results in
updating the following arguments: resource&state
per active participation of W-context of the Web
service (Table 1) and number of active component
Web services of R-context of the resource.
01: Policy (Aspect=”PermissionDeployment”)
02: <Rule xmlns=”urn:oasis:names:tc:xacml:3.0:per-
mission:policy:schema:wd:01”
03: xmlns:proc=”permission-deployment” RuleId=”Pe
rmissionDeploymentWS”>
04: <Condition>
05: <Apply FunctionId=”and”>
06: <Apply FunctionId=”integer-less-than”
DataType=”boolean”>
07: <SubjectAttributeDesignator AttributeId=”Numbe
rofActiveComponentWebServices”
08: DataType=”integer”>
09: <SubjectAttributeDesignator AttributeId=”Maximu
mNumberofComponentWebServices”
10: DataType=”integer”>
11: </Apply>
12: <SubjectAttributeDesignator AttributeId=”NextAc
ceptanceofComponentWebServices”
13: DataType=”boolean”>
14: </Apply>
15: </Condition>
16: <Conclusions>

17: <TrueConclusion>
18: <proc:do> yes-permission-deployment </proc:
do>
19: </TrueConclusion>
20: <FalseConclusion>
21: <proc:do> no-permission-deployment </proc:do>
22: </FalseConclusion>
23: </Conclusions>
24: </Rule>
Deployment Policy for Restriction.
It consists of preventing a Web service form being
executed over a resource. Besides the example
of resource failure, restrictions could be geared
towards the reinforcement of the execution clauses
that are agreed upon between a Web service and
a resource. For example a Web service binds a
resource for execution before the scheduled time.
The following illustrates a deployment policy for
restriction in WSPL. It states that a Web service
can be restricted from execution subject to evalu-
ating <Condition> to true. This condition checks
that a positive permission (line 04) of execution
has been issued (line 06) and the agreed execu-
tion time is valid. The execution time of a Web
385
A Context-Based and Policy-Driven Method to Design and Develop Composite Web Services
VHUYLFHLVLGHQWL¿HGXVLQJQH[WFRPSRQHQW:HE
services per active participation argument of R-
context of the resource.
01: Policy (Aspect=”RestrictionDeployment”)

02: <Rule xmlns=”urn:oasis:names:tc:xacml:3.0:gen-
eralization:policy:schema:wd:01”
03: RuleId=”RestrictionDeploymentWS”>
04: <Condition>
05: <Apply FunctionId=”and”>
06: <SubjectAttributeDesignator AttributeId=”YesPer
missionDeployment”
07: DataType=”boolean”>
08: <Apply FunctionId=”equal” DataType=”boolean”>
09: <SubjectAttributeDesignator AttributeId=”Executi
onTime” DataType=”String”>
10: </Apply>
11: </Apply>
12: </Condition>
13: <Conclusions>
14: <TrueConclusion RestrictionDeployment = “No”>
15: <FalseConclusion RestrictionDeployment =
“Yes”>
16: </Conclusions>
17: </Rule>
CP4WS TO IMPLEMENT AMIN
SCENARIO
We discuss the work we carried out following the
use of CP4WS to design the system implement-
ing Amin scenario. For compatibility purposes,
Sun Microsystems’s tools are used: J2EE 1.4 to
develop Web services and XACML Open Source
to develop policies. Figure 5 illustrates the archi-
tecture of this system that comprises four types
of managers. It should be noted that the role

RIHDFKPDQDJHULVDVVRFLDWHGZLWKDVSHFL¿F
step in CP4WS. Figure 6 shows some snapshots
related to the use of the system implementing
Amin scenario.
The VSHFL¿FDWLRQPDQDJHU supports design-
HUVGXULQJWKHVSHFL¿FDWLRQRIFRPSRVLWH:HE
services. This calls for identifying the appropri-
DWHFRPSRQHQW:HEVHUYLFHV7KHVSHFL¿FDWLRQ
work is carried out through a composition
environment, which is a set of integrated tools
that assist designers create and edit new and ex-
LVWLQJVSHFL¿FDWLRQVRIFRPSRVLWH:HEVHUYLFHV
respectively. We use a composition environment
that was developed in one of our previous proj-
ects (Maamar, 2006e). This environment, also,
supports translating composite Web service
VSHFL¿FDWLRQVOLNHWKHRQHVKRZQLQ)LJXUH
LQWR%3(/VSHFL¿FDWLRQ
The selection manager is responsible for
identifying the component Web services that
satisfy user needs. This manager is triggered upon
XVHU¶VUHTXHVWDQGLGHQWL¿FDWLRQRIWKHDSSURSUL-
DWHFRPSRVLWH:HEVHUYLFHVSHFL¿FDWLRQ,QWKH
current system, the selection is not only driven
by the resulting functionality of the composition
the user needs (e.g., to reach a meeting place by
taxi or by bus according to weather conditions).
It also considers Web services QoS parameters
that affect the selection process like response
time, performance, and throughput. These con-

straints are expressed with WSPL policies. The
policy manager makes Web services bind to
appropriate behaviors according to the progress
of a composition.
Finally, the context manager keeps track of
the contexts of users, Web services, and resources.
Contexts’ arguments are of different types and
their values change over time. Figure 7 illus-
WUDWHVWKHVSHFL¿FDWLRQRIW-context of Weather
WS using the prototype. Therefore, the context
manager is supported with a real-time triggering
mechanism that feeds context parameters with
fresh values. Details of contexts are structured
DV;0/¿OHV%HIRUHVHQGLQJWKHVHOHFWHG:HE
services’ addresses to the user for invocation, the
policy manager ensures that these Web services
comply with the policies reported previously.
Upon approval of the policy manager, the selec-
tion manager initiates the search of the resources
on which the Web services will operate. Figure 8
386
A Context-Based and Policy-Driven Method to Design and Develop Composite Web Services
User
Specification
manager
2. Submission
Selection
Manager
1. Request
3. Selection

Policy
Manager
4. Verification
Repository of
Web services
Context
Manager
Binding
Binding
Repository of
resources
5. Search
6. Services for invocation
Composite
level
Component
level
Binding
Approval(yes,no)
Figure 5. Architecture of the system implementing Amin scenario
Figure 6. Snapshots from the prototype
387
A Context-Based and Policy-Driven Method to Design and Develop Composite Web Services
shows parts of the policy that restricts the execu-
tion of Weather WS on a resource.
RELATED WORK
Web services are a very active area of Research
and Development. However, to our knowledge,
few projects have aimed at suggesting design
and development methods for Web services

based on context and driven by policies. We
present in the following some projects that helped
shape the steps and annotations of CP4WS. These
projects mainly target design and development
methods.
In CP4WS, context is part of the exercise of
modeling composite Web services. Other projects
such as (Brenner, 2003) use Web services to man-
aging context provisioning. Breener and Schiffers
envision that context information will typically
be provided by autonomous organizations (or
context providers), which means heterogeneity and
distribution challenges to deal with. Additional
challenges are cited in (Brenner, 2003) including
what is the optimal sequence for gathering and
combining the required context information, how
to secure the whole context provisioning process,
and how is the cooperation between the providers
of context achieved, and even enforced?
In (Baresi, 2005), Baresi et al. propose a
policy-based approach to monitor Web services’
functional (e.g., constraints on exchanged data)
and non-functional (e.g., security, reliability) re-
quirements. In this approach Baresi et al. report on
WKHGLIIHUHQWW\SHVRISROLFLHVWKDWFDQEHGH¿QHG
along the life cycle of a Web service (Mukhi, 2004).
These types are service policies, server policies,
supported policies, and requested policies.
In (UWA, 2002), the Ubiquitous Web Appli-
cations (UWA) Consortium proposes a frame-

work that comprises several methodologies,
meta-models, and tools for designing ubiquitous
Web applications. Organization and execution
models permit designing the business processes
that underlay such applications. The organiza-
tion model expresses the hierarchical relations
between activities of the same business process.
These relations are described using an UML class
diagram. In addition some properties (e.g., ACID
properties) can be associated with each activity.
The execution model describes the possible execu-
WLRQÀRZVRIWKHGLIIHUHQWDFWLYLWLHVWKDWFRPSRVH
WKHRUJDQL]DWLRQPRGHO7KHVHÀRZVFRQVWLWXWHWKH
dynamic aspect of the business process and are
expressed using an UML activity diagram.
In (Brambilla, 2006), Brambilla et al. propose
a Web engineering method for the high-level
VSHFL¿FDWLRQRISURFHVVHVDQG:HEVHUYLFHVEDVHG
applications. This method relies on extending the
Web Modeling Notation (WebML (Ceri, 2000))
with standard process modeling concepts and Web
services-based application distribution primitives.
Process modeling concepts expressed in the Busi-
ness Process Modeling Notation (
n.
org) are added to WebML so, process requirements
in terms of interactions over the Web are expressed.
Web services are used as a means to deal with the
process distribution requirements. Interesting to
note that this method has been implemented as a

case tool through the use of WebRatio (
http://www.
WebRatio.com).
In (Detroyer, 2003), De Troyer and Casteleyn
work on an adaptation of the existing Web Site
Design Method (WSDM). The objective is to
model complex business processes in the context
of Web applications and to support some advanced
features like transactions and persistence of pro-
cesses. Task modeling and navigational design,
which are the core steps in the conceptual design
of WSDM, have been changed to accommodate
the requirements of modeling complex processes.
The ConcurTaskTrees (CTT) notation (Paterno,
LVPRGL¿HGWRRQO\FRQVLGHUWKUHHFDWHJRULHV
of tasks: application, interaction, and abstract.
Abstract task refers to the task that needs to be
decomposed. Application and interaction tasks
refer to the tasks executed by applications and
users respectively. The navigation structure that
388
A Context-Based and Policy-Driven Method to Design and Develop Composite Web Services
Figure 7. W-context of Weather Web Service
<rdf:RDF
xmlns:WC= sattanathan/OWLC/Context/WC#
xmlns:rdf= /><rdf:Description rdf:about=”http://defaultURI/WC#”>
<WC:CorrectiveActionsPerFailureType>Nil</WC:CorrectiveActionsPerFailureType>
<WC:ResourceAndStatePerActiveParticipation>Resource1/Suspended
</WC:ResourceAndStatePerActiveParticipation>
<WC:MaximumNumberOfParticipations>10</WC:MaximumNumberOfParticipations>

<WC:ReasonsOfFailurePerActiveParticipation>Nil</WC:ReasonsOfFailurePerActiveParticipation>
<WC:RegularActions>Book Taxi</WC:RegularActions>
<WC:PrevisousWebServicesPerActiveParticipation>Nil
</WC:PrevisousWebServicesPerActiveParticipation>
<WC:NextWebServicePerActiveParticipation>TAxi or Bus Schedule
</WC:NextWebServicePerActiveParticipation>
<WC:Label>WEather</WC:Label>
<WC:Date>Dec 25, 2005 6:28:39 PM</WC:Date>
<WC:CurrentWebServicesPerActiveParticipation>Location
<WC:NextPossibiliyOfParticipation>Possible</WC:NextPossibiliyOfParticipation>
<WC:NumberOfActiveParticipations>7</WC:NumberOfActiveParticipations>
</rdf:Description>
</rdf:RDF>
Figure 8 . Restriction Policy on Weather Web Service
<Policy PolicyId=”Restriction”
RuleCombiningAlgId=”urn:oasis:names:tc:xacml:1.0:rule-combining-algorithm:ordered-permit-over-
rides”>
<Description>Restriction policy on WEather Web Service</Description>
<Target>
<Subjects>
<Subject>
<SubjectMatch MatchId=”urn:oasis:names:tc:xacml:1.0:function:rfc822Name-match”>
<AttributeValue DataType=” #string”>users.example.com</AttributeValue>
<SubjectAttributeDesignator AttributeId=”urn:oasis:names:tc:xacml:1.0:subject:subject-id”
DataType=”urn:oasis:names:tc:xacml:1.0:data-type:rfc822Name”/>
</SubjectMatch>
</Subject>
</Subjects>
<Resources>
<Resource>

<ResourceMatch MatchId=”urn:oasis:names:tc:xacml:1.0:function:anyURI-equal”>
<AttributeValue DataType=” #anyURI”> />Value>
<ResourceAttributeDesignator AttributeId=”urn:oasis:names:tc:xacml:1.0:resource:resource-id”
DataType=” /> </ResourceMatch>
</Resource>
</Resources>
<Actions>
<AnyAction/>
</Actions>
</Target>
<Rule RuleId=”RestrictionWS” Effect=”No”>
<Target>
389
A Context-Based and Policy-Driven Method to Design and Develop Composite Web Services
describes how a user should perform tasks, is then
automatically generated for different users from
the CTT augmented with temporal relationships
between the different tasks.
In (Cappiello, 2006), Cappiello and Pernici
suggest a method to solve run-time data quality
problems in self-healing Web services environments.
Failures due to run-time data quality problems are
detected and the proposed method produces a list
of recovery actions for quality improvements. The
main step in the method concerns working on the
warning message generator, which is in charge of
monitoring the system, detecting all the anomalies
that occur in data management, and identifying the
sources of data quality problems.
A framework for analyzing and comparing

Web application design methodologies is pre-
sented in (Distante, 2007). Distante et al. present
the business/user/system requirements for de-
signing business process. Business requirements
FRUUHVSRQGWRWKHLGHQWL¿FDWLRQRIWKHGLIIHUHQW
activities included in a given Web transaction
and their semantic associations, and the logical/
temporal order in which such activities must be
executed by the user. User requirements include
WKHVSHFL¿FDWLRQRIWKHVHWRIDFWLYLWLHVZKLFKFDQ
be suspended and resumed in case of long-lived
transactions, and the description of how an activity
can be customized depending on the state of the
ongoing transaction. The system requirements
UHIHUWRWKHGH¿QLWLRQRIWKHLQIRUPDWLRQREMHFWV
affected by the execution of an activity, and the
GH¿QLWLRQDQGWKHPDQDJHPHQWRIWKHVWDWHVRID
Web transaction. These design requirements are
then used to evaluate and compare two Web ap-
plication design methodologies, namely OOHDM
(Schmid, 2004) and UWA (UWA, 2002).
To wrap up this related work section, we
highlight again the features of CP4WS per
step. Five steps were developed. The first step
uses UML use-cases to identify and specify
users' needs. The second step uses service
chart diagrams and state chart diagrams to
specify the orchestration of the component
Web services that constitute a composite Web
service. The third step defines the arguments

that form the context of the component Web
services and of other participants like users and
resources that interact with these component
Web services. The fourth step uses WSPL to
specify the policies that manage the behavior
that the component Web services expose to
the external environment. Finally, the last step
uses WSPL again to manage the performance
of the component Web services on top of the
computing resources.
CONCLUSION
In this chapter, we presented our CP4WS method
that targets those who are responsible for the
design and development of information systems
based on Web Services. We discussed how com-
position of Web services permits addressing the
VLWXDWLRQRIDXVHU¶VUHTXHVWWKDWFDQQRWEHVDWLV¿HG
by any single, available Web service, whereas a
composite Web service obtained by combining
a set of available Web services might be used.
The core concepts of CP4WS are context, policy,
service chart diagram, state chart diagram, and
UHVRXUFH&3:6FRQVLVWVRI¿YHVWHSVXVHUQHHGV
LGHQWL¿FDWLRQ DQG VSHFL¿FDWLRQ :HE VHUYLFHV
orchestration, Web services contextualization,
:HE VHUYLFHV EHKDYLRU VSHFL¿FDWLRQ DQG :HE
services deployment.
As part of our future work, we aim at adding
WZRPRUHVWHSVWR&3:67KH¿UVWVWHSZRXOG
be dedicated to managing the exceptions that the

multiple participants in Web services composition
arise. First, there is no guarantee that a particular Web
service is still available at time of request. A provider
could withdraw its Web service without prior notice.
6HFRQGWKHUHLVQRJXDUDQWHHWKDWWKHVSHFL¿FDWLRQ
RIDFRPSRVLWH:HEVHU YLFHLVHU URUI UHH&RQ ÀLFWLQJ 
actions like concurrent acceptance and rejection, and
GHDGORFNVPD\RFFXUGXULQJWKLVVSHFL¿FDWLRQH[HFX-
tion. Finally, there is no guarantee that a particular
390
A Context-Based and Policy-Driven Method to Design and Develop Composite Web Services
resource is up at time of execution of a Web service.
A resource could be down due to power failure. The
various examples back the importance of an addi-
tional step on exception handling in CP4WS. The
second step would be concerned with guidelines for
backing the correct execution of a transactional Web
service during the design phase. For this purpose we
suggest mapping these guidelines onto transactional
properties (compensatable, retriable, and pivot) that
will be associated with Web services. The role of
DWUDQVDFWLRQDOSURSHUW\LVWRGH¿QHWKHDFFHSWDEOH
behavior of a Web service. For example the failure
of a Web service could be tolerated in one scenario
but not in another one. Transactional properties that
can be associated to a Web service and a forward
adaptation algorithm to support rolling back strategy
in some complex situations are presented in detail
in (Maamar, 2007).
ACKNOWLEDGMENT

The authors would like to thank the reviewers
for their comments and suggestions of changes.
7KHGHYHORSPHQWRI&3:6EHQH¿WHGIURPWKH
fruitful discussions the authors had with A. An-
derson, G. Kouadri-Mostéfaoui, Ph. Thiran, and
S. Sattanathan.
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Chapter 2.5
Dynamic Pricing for
E-Commerce
Prithviraj Dasgupta
University of Nebraska, Omaha, USA
Louise E. Moser
University of California, Santa Barbara, USA
P. Michael Melliar-Smith
University of California, Santa Barbara, USA
INTRODUCTION
Over the last decade, H  FR P P HU FH KD VV LJ Q L ¿F D Q WO\ 
changed the traditional forms of interaction among
humans in conducting business by automating
business processes over the Internet. Early seller
Web sites consisted of passive text-based catalogs
of products that could be manually browsed by
potential customers. Online passive catalogs were
soon replaced by dynamically updated catalogs
containing detailed product descriptions using
combinations of text and images that could be
searched in various formats and according to

different search criteria. E-commerce techniques
used by sellers for operations such as price set-
ting, negotiation, and payment have matured
from manual off-line processing of sales data to
automated algorithms that dynamically determine
SULFHVDQGSUR¿WVIRUVHOOHUV0RGHUQHFRPPHUFH
processes for trading goods between buyers and
VHOOHUV FDQ EH GLYLGHG LQWR ¿YH VWDJHV VHDUFK
valuation, negotiation, payment, and delivery.
Depending on the type of market in which the
goods are traded, some of the above stages are
more important than others.
There are three principal market models that
are used for online trading. The most common
market model used by online sellers for trading
goods over the Internet is the posted-price market
model. The other two market models, the auction
model (Sandholm, Suri, Gilpin, & Levine, 2002)
and the marketplace model (Chavez & Maes,
1996), are used for markets in which niche or
specialty items with sporadic or uncertain demand
are traded.
In the posted-price market model, a seller
announces the price of a product on its Web site.
Buyers visiting the seller’s Web site request a
quote from the seller. The seller responds with
a quote in response to the buyers’ requests, and
the buyers examine the seller’s quote to make a
purchase decision. Unlike auctions and market-