CP4WS manages the deployment of Web services on resources with policies.. This condition refers to some arguments like number of active component Web services line 07 that the resource s
Trang 1step 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-permispermis-sion-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: < A p p l y F u n c t i o n I d = ” i n t e g e r - l e s s - t h a n ” 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 execuexecu-tion time of a Web
Trang 2VHUYLFHLVLGHQWL¿HGXVLQJQH[WFRPSRQHQW: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¿FDWLRQPDQDJHU supports
design-HUV GXULQJ WKH VSHFL¿FDWLRQ RI FRPSRVLWH :HE
services This calls for identifying the appropri-DWHFRPSRQHQW:HEVHUYLFHV7KHVSHFL¿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-LVWLQJVSHFL¿FDWLRQVRIFRPSRVLWH:HEVHUYLFHV 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¶VUHTXHVWDQGLGHQWL¿FDWLRQRIWKHDSSURSUL-DWHFRPSRVLWH:HEVHUYLFHVSHFL¿FDWLRQ,QWKH 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-WUDWHVWKHVSHFL¿FDWLRQRIW-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%HIRUHVHQGLQJWKHVHOHFWHG: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
Trang 3Specification manager 2 Submission Selection
Manager
1 Request
Policy Manager
4 Verification Repository of
Web services
Context Manager
resources
5 Search
6 Services for invocation
Binding
Approval(yes,no)
Figure 5 Architecture of the system implementing Amin scenario
Figure 6 Snapshots from the prototype
Trang 4shows 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
WKHGLIIHUHQWW\SHVRISROLFLHVWKDWFDQEHGH¿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 relaorganiza-tions 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-WLRQÀRZVRIWKHGLIIHUHQWDFWLYLWLHVWKDWFRPSRVH WKHRUJDQL]DWLRQPRGHO7KHVHÀRZVFRQVWLWXWHWKH 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¿FDWLRQRISURFHVVHVDQG:HEVHUYLFHVEDVHG 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 (http://www.bpmn 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,
LVPRGL¿HGWRRQO\FRQVLGHUWKUHHFDWHJRULHV
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
Trang 5Figure 7 W-context of Weather Web Service
<rdf:RDF
xmlns:WC=http://www.nitk.ac.in/ sattanathan/OWLC/Context/WC#
xmlns:rdf=http://www.w3.org/1999/02/22-rdf-syntax-ns#
<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=”http://w3.org/ #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=”http://w3.org/ #anyURI”>http://webservice.weather.com/</Attribute-Value>
<ResourceAttributeDesignator AttributeId=”urn:oasis:names:tc:xacml:1.0:resource:resource-id”
DataType=”http://www.w3.org/2001/XMLSchema#anyURI”/>
</ResourceMatch>
</Resource>
</Resources>
<Actions>
<AnyAction/>
</Actions>
</Target>
<Rule RuleId=”RestrictionWS” Effect=”No”>
<Target>
Trang 6describes 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
FRUUHVSRQGWRWKHLGHQWL¿FDWLRQRIWKHGLIIHUHQW
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
WKHVSHFL¿FDWLRQRIWKHVHWRIDFWLYLWLHVZKLFKFDQ
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
UHIHUWRWKHGH¿QLWLRQRIWKHLQIRUPDWLRQREMHFWV
affected by the execution of an activity, and the
GH¿QLWLRQDQGWKHPDQDJHPHQWRIWKHVWDWHVRID
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 VLWXDWLRQRIDXVHU¶VUHTXHVWWKDWFDQQRWEHVDWLV¿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&3:6FRQVLVWVRI¿YHVWHSV XVHUQHHGV 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 6HFRQGWKHUHLVQRJXDUDQWHHWKDWWKHVSHFL¿FDWLRQ RIDFRPSRVLWH:HEVHUYLFHLVHUURUIUHH&RQÀLFWLQJ actions like concurrent acceptance and rejection, and GHDGORFNVPD\RFFXUGXULQJWKLVVSHFL¿FDWLRQH[HFX-tion Finally, there is no guarantee that a particular
Trang 7resource 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
DWUDQVDFWLRQDOSURSHUW\LVWRGH¿QHWKHDFFHSWDEOH
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
7KHGHYHORSPHQWRI&3:6EHQH¿WHGIURPWKH
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, HFRPPHUFHKDVVLJQL¿FDQWO\
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
SULFHVDQGSUR¿WVIRUVHOOHUV0RGHUQHFRPPHUFH
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
... services Software and System Modeling Journal Special Section on“Service-Based Software and Systems Engineer-ing, 5(2).
Maamar, Z and Benslimane, D and Anderson,
A... 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... Proceedings of The 6th
International Conference on Electronic
Com-merce and Web Technologies (EC-Web).
Anderson, A H (2004) An introduction to the
Web