OntoWeaver-S: Integrating Web Services into Data-Intensive Web Sites
Yuangui Lei, Enrico Motta, John Domingue
Knowledge Media Institute
the Open University
Milton Keynes, MK7 6AA
{y.lei, e.motta, j.b.domingue}@open.ac.uk
ABSTRACT descriptions specify how to invoke a service and
Designing web sites is a complex task. Ad-hoc rapid SOAP/XML [22] provides a uniform and standardised
prototyping easily leads to unsatisfactory results, e.g. communication mechanisms, thus enabling easy
poor maintainability and extensibility. However, existing interoperability. However, if a developer wants to bring
web design frameworks focus exclusively on data web services into web sites, essentially he or she needs to
presentation: the development of specific functionalities is do it entirely through low-level programming. With the
still achieved through low-level programming. In this partial exception of WebML [3], none of the design
paper we address this issue by describing our work on the frameworks mentioned above provides hooks to augment
integration of (semantic) web services into a web design web sites with functionalities, based on web service
framework, OntoWeaver. The resulting architecture, technology. Indeed, while WebML provides mechanisms
OntoWeaver-S, supports rapid prototyping of service- to communicate with web services, the overall data-driven
centred data-intensive web sites, which allow access to design framework has not been modified. For example,
remote web services. In particular, OntoWeaver-S is the user interface constructs have not been extended for
integrated with a comprehensive web service platform, enabling the access of remote web services. In other
IRS-II, for the specification, discovery, and execution of words, as far as WebML is concerned, web services are
web services. Moreover, it employs a set of not part of the design framework; they are simply
comprehensive site ontologies to model and represent all functionalities, which can be invoked, much like any
aspects of service-centred data-intensive web sites, and other web application.
thus is able to offer high level support for the design and A number of web service platforms have been
development process. developed to support the design, the publication, and the
invocation of web services. Examples include the Java
1. Introduction Web Services Developer Pack (JWSDP) [12] and the
IBM Web Services Toolkit (WSTK) [10]. However these
Designing web sites is a complex task. Ad-hoc rapid platforms are very different from the web site design
prototyping approaches easily lead to unsatisfactory frameworks mentioned above. Their role is to provide
results, e.g. poor maintainability and extensibility. As a powerful programming environment to build applications
consequence, a number of structured methodologies have based on web services, rather than providing high level
been proposed to facilitate and guide the design and web site design support. Thus, we believe there is a need
development processes [20, 8, 4, 9]. In particular, a of integrating web service technology into high level web
number of methodologies and tools have been developed site design frameworks to facilitate the specification of
to support the design of data-driven web sites at a high data-intensive web sites, which allow the access to remote
level of abstraction. Examples include RMM [11], web services and the presentation of the results of web
OOHDM [21], ARANEUS [2], WebML [5], OntoWebber services. So, our goal is to define mechanisms, which
[13], and HERA [7]. The key feature of these approaches allow easy integration of web services into a structured,
is that they provide high level support for web site design, high level support for web site design. In order to achieve
from conceptualisation and specification down to this goal we make use of semantic web services [1, 6, 17],
maintenance, by properly distinguishing between the which rely on semantic descriptions describing the
different dimensions of web design and by organizing the functionalities of web services in a much more powerful
development activities into well-structured processes. way than what available in WSDL/UDDI. Hence, by
However, these approaches focus exclusively on data making use of semantic web services we can then provide
presentation: the development of specific functionalities is high level support for bringing functionalities into a web
still achieved through low-level programming. site, by focusing the interaction with the user (i.e., the
Web service technology [24, 23, 22, 10, 12] enables web site developer) on the semantic aspects, rather than
access to remote content and application functionalities, on the technical and implementation details. In particular,
independently of specific implementations, or data we will take OntoWeaver [14, 15, 16], a sophisticated
formats. Standardised registry mechanisms (e.g., in UDDI data-driven web design framework, as our starting point,
[23]) specify the location of a service. WSDL [24] and we will augment it to support the high level
integration of semantic web services into web sites. We specification of customization requirements.
will call the resulting, extended architecture, OntoWeaver makes use of a customization engine to
OntoWeaver-S. apply the specified rules to reason upon the site
The paper is organized as follows: section 2 describes specifications according to the valuable user profiles
the criteria we used to progress from OntoWeaver to (i.e. instantiations of the user models) to provide
OntoWeaver-S; section 3 presents the OntoWeaver-S customization support.
approach to modelling the typical user interfaces of
service-centred data-intensive web sites; section 4 OntoWeaver employs RDFS [19] and RDF [18] to
discusses the implementation of the OntoWeaver-S represent ontologies and specifications. Moreover, it
mechanisms, which support the integration of web offers a tool infrastructure to support the entire life-cycle
services into data-intensive web sites; and finally section of a customized data-intensive web site at a high level,
5 and section 6 describe related work and reiterate the including modelling, design, and maintenance. More
main conclusions from this work. information about OntoWeaver can be found in [14, 15,
16]. Like other web modelling approaches mentioned
2. From OntoWeaver to OntoWeaver-S earlier, OntoWeaver focuses on data presentation and
does not offer high level support for bringing web
2.1. OntoWeaver services into web sites.
OntoWeaver approaches data-intensive web sites with 2.2. Evolution
special focuses on dynamic data content manipulation (i.e.
data content publishing, querying, and updating), user The main goal of OntoWeaver-S is to provide high
interface composition, and customization design. In level support for the design of web sites that can access
particular, it provides a site view ontology and a remote web services. Obviously, like OntoWeaver,
presentation ontology to enable the declarative OntoWeaver-S is also a web design framework, which
representation of data-intensive web sites. Moreover, provides explicit models to provide high level support for
OntoWeaver proposes a generic customization framework the design of web sites. Hence, the design principles of
for offering high level support for the specification of OntoWeaver-S are very much the same as OntoWeaver.
customization requirements and for offering For example, the modular design architecture, which
comprehensive customization support for web distinguishes different models to approach web site
applications at run time. design, remains the same. The presentation ontology and
The specification of a web site in OntoWeaver consists the customization framework do not need to be adapted
of four perspectives: either, as they abstract the common features of the
− The Domain Model abstracts the back-end data sources. presentation design and the customization design of web
It contains a set of abstract concepts and relations, sites.
representing data structures of the problem domain. On the other hand, the focus of OntoWeaver-S is on
the integration of web services into data-intensive web
− The Site View Model describes navigational structures
sites. Hence, in moving from OntoWeaver to
for web applications and compositional user interfaces
OntoWeaver-S we have to introduce a number of
for web pages in terms of the site view ontology. In
changes:
particular, the site view ontology provides a set of
• The site view ontology, which describes navigational
atomic user interface constructs as well as a set of
structures and user interfaces, should be adapted to
composite user interface constructs to enable the fine-
support the design of the site view model for service
grained level support for the composition of complex
centred web sites. In particular, it should allow the
user interfaces. Moreover, it provides a set of dynamic
high level specification of web services within the
user interface to facilitate the specification of dynamic
user interface elements of target web sites.
features for data-intensive web sites, including
querying and manipulating the underlying domain • The tool infrastructure should be adapted towards the
databases. goal of design and development of service centred
web sites. In particular, the Site Designer should be
− The Presentation Model specifies the visual appearance
modified to offer support for the design and
and layout for each component in the site view model
development of this new kind of web sites. At the
in terms of the presentation ontology.
same time, a new run-time tool is needed to integrate
− The Customization Model specifies customization web services into web sites.
requirements for personalizing web pages towards
individual users. It relies on the OntoWeaver As already mentioned, to enable the high level
customization framework, which employs a user specification of web services in target web sites,
model, a customization rule model, and a declarative OntoWeaver-S needs the support of semantic descriptions
site model to enable the high level support for the describing web services. As a result, the service layer
upon which site view models are built should be semantic. tool, called Service Integrator, to integrate IRS-II with
Moreover, in order to integrate web services into the data-intensive web sites. Specifically, the Service
target web site, OntoWeaver-S needs frameworks and Integrator collects information from a web site, then calls
tools supporting the discovery and invocation of the IRS-II server (by means of IRS-II APIs) to invoke the
appropriate web services by reasoning about their specified web service and gets results from IRS-II, and
semantic descriptions. The IRS-II framework [17], which finally it passes the service results back to the web site.
will be introduced in the next section, comes right in to fit
the OntoWeaver-S framework.
An
2.3. Integrating Web Services into Data-Intensive OntoWeaver-S
Generated Data-
OntoWeaver-S
IRS-II Finding
Service
Web Sites Intensive Web Site
Integrator
Server Flights
IRS-II [17] is an implemented infrastructure, which
Figure 1 The process of accessing web services in
has been developed in our lab, the Knowledge Media
OntoWeaver-S generated data-intensive web sites
Institute (http://kmi.open.ac.uk). It supports the
publication, discovery, and execution of semantic web
services. The following informal specification shows the OntoWeaver-S relies on a set of constructs, such as
task description of a semantic web service, which answers DataComponent and KAComponent, to describe the user
requests for flights in accordance with the given user interfaces for accessing web services and publishing
requirements. results. These user interface constructs will be described
Task Ontology: flight-service in the next section.
Task Name: find-flights
Input Roles: from-place (type: city)
to-place (type: city) Site
depart-time (type: time-point) hasIndexResource hasTask
arrival-time (type: time-point) hasResource
budget (type: amount-of-money)
Output Roles: flights (type: Flight) SiteResource Task
hasMetaData
To invoke this semantic web service, a user simply hasComponent
asks for the task to be achieved in terms of the task name MetaData
hasSubComponent
ResourceComponent
find-flights and the task ontology name flight-service, the
IRS-II broker then selects an appropriate problem solving hasSubResource
hasCommand
method (PSM) and then uses grounding information to hasOutput
hasInput
locate and invoke the corresponding web service – see
[17] for a detailed description of IRS-II. In particular, the SubResource Output Input Command
hasTask
input roles carry parameters for executing the hasLinkItem
hasTask hasTask
corresponding web service; the output roles store the LinkItem Task
service results. Please note that IRS-II only supports one
output role at the moment. The data type of the output
role can be primitive e.g. String, Integer, or non-primitive, Figure 2 An overview of the OntoWeaver-S site
i.e. being domain classes. When the data type of the view ontology
output role is not primitive, IRS-II uses XML to represent
service results. For example, IRS-II uses XML to
represent the results of the web service find-flights, which
are instances of the class Flight. This class has been 3. Modelling Typical User Interfaces for
defined in the domain ontology of the semantic web Accessing Web Services
service.
OntoWeaver-S employs IRS-II as a platform to
Like OntoWeaver, OntoWeaver-S offers a site view
integrate web services into data-intensive web sites. On
ontology and a presentation ontology to allow the
the one hand, OntoWeaver-S relies on IRS-II to enable
declarative representation of all aspects of service-centred
the access of remote web services, as IRS-II is able to
data-intensive web sites. As shown in figure 2, the site
locate and invoke remote web services and pass results
view ontology consists of a set of navigational constructs,
back. On the other hand, OntoWeaver-S uses IRS-II as a
which facilitate the composition of navigational
platform to allow the provision of web services for data-
structures, and a set of user interface constructs, which
intensive web sites.
support the composition of user interfaces. In particular,
Figure 1 shows the process of accessing remote web
the site view ontology has been extended to model
services in an OntoWeaver-S generated data-intensive
service-centred data-intensive web sites. Specifically, a
web site. In particular, OntoWeaver-S provides a run-time
set of user interface constructs have been extended to
allow the modelling of the typical user interfaces of entity. The following RDF [18] code defines one
service-centred data-intensive web sites, including dynamic output element for publishing dynamic
information visualization, which allows the visualization content of airline, which is one result field of the task
of dynamic data content coming from the underlying find-flights (the namespace prefix 'svo' in this paper
databases or remote web services, and information refers to the namespace of the OntoWeaver site view
provision, which allows the provision of information for ontology:
updating or querying the back-end domain data sources or xmlns:svo=”http://kmi.open.ac.uk/people/yuangui/sit
for invoking remote web services. eviewontology#”).
The navigational constructs are made up of Site, which
models a site view as a collection of site resources i.e.
web pages and a collection of task instances i.e. text
descriptions of semantic web services, SiteResource,
which abstracts web pages as nodes in the navigational
network and as units of user interface composition, and
LinkItem and DynamicLinkItem, which model the static or • Output describes the basic user interface elements
dynamic link relationship between web pages. In addition, that present static information. Output elements are
the constructs Parameter and ParameterClause are used to present explanations for dynamic values in
proposed to allow the specification of contextual links data components.
between pages. More information about the site structure • OutputComponent describes the composite user
modelling can be found in [17]. interface element for publishing the value of the
The user interface constructs can be classified into specified slot of the given class entity or the value of
atomic constructs, which abstract basic user interface the specified output role of the given web service. An
elements that can not be further decomposed into other output component typically comprises an output
elements, and composite constructs, which model element, which presents explanations about the
composite user interface elements. On one hand, these dynamic content, and a dynamic element, which
user interface constructs can provide a fine grained level displays the dynamic content.
support for user interface composition. On the other hand, • DataComponent abstracts the composite user
these constructs support the high level specification of interface elements that visualize instances of a
access to semantic web services. Specifically, within the specified class entity or results of a specified web
user interface constructs, remote web services are service.
described in terms of tasks, input roles, and output roles,
which comply with the semantic representation approach
employed in IRS-II [17]. Please note that the concept of
output role in OntoWeaver-S is slightly different from
IRS-II, when the data type of the output role of a web
service is not a primitive data type but a class entity,
which has a number of slots. In this case, the output roles
in OntoWeaver-S refer to the slots of the result instances
of the corresponding web service.
3.1. Information Visualization Figure 3 An user interface example for visualizing
the results of the web service find-flights
Information visualization in service-centred data- Figure 3 shows an example user interface for
intensive web sites presents dynamic information, which visualizing the results of the web service find-flights.
comes from the underlying databases, web resources or This user interface contains a number of dynamic output
remote web services. OntoWeaver-S relies on the elements for visualizing the values of the web service
following constructs to enable the composition of the user find-flights. The following code illustrates the
interfaces for information visualization: composition of this data component. Please note that at
• DynamicOutput models the basic user interface this stage, the layout of user interface elements is not
elements that present the dynamic value of the considered.
specified slot of a given class entity or the dynamic
value of the specified output role of a given web
service. It has a number of attributes: the attributes provision for the specified slot of the given domain
class entity or for the specified input role of the
… associated service. An input component typically
field and an output element for presenting an
explanation about the input field.
…
• KAComponent, which models the composite user
3.2. Information Provision interface elements that present forms for achieving
the functionality of information provision. A
The information provision is realized through knowledge acquisition component is typically made
knowledge acquisition forms, which allow users to submit up of a set of input components and a command
information to web sites. The submitted information can element.
be records of the underling databases or information for
invoking the specified service. Please note that in this Figure 4 shows an example user interface for accessing
context, the service can be a built-in service provided by the remote web service find-flights. The user interface is
OntoWeaver-S or a remote web service, which has been made up of a number of input fields and a command
made available through IRS-II [17]. OntoWeaver-S button for allow end users to invoke the web service. The
provides a set of built-in services for inserting data into following code illustrates the composition of this user
the underlying databases and making queries over the interface.
underlying databases. Hence, a knowledge acquisition
component can be used for information provision,
information query and web services access. OntoWeaver-
S relies on a set of constructs to model the composition of
knowledge acquisition forms:
• Input, which abstracts the actual input fields for
allowing end users specifying information for
particular slots of the specified domain class entity or
for particular input roles of the specified web service.
The following example defines an input element, Figure 4 An user interface example for accessing
which allows end users to enter information for the the web service find-flights
input role of fromplace for the web service find-
flights.
……
• Command, which describes the interface elements for
submitting information. In particular, the definition of
a command element indicates the associated service
and the result page node, which intends to publish
earlier, the associated service can be a built-in service
Figure 5 The process of accessing web services ……
and publishing dynamic results coming from web
services
Each data component is mapped to an HTML table to
publish dynamic content coming from the associated
4.1. Web Service Integration Process semantic web service. Moreover, additional server-side
code is generated at the same time to enable the access of
In this section, we get a closer look at the process of the specified web service and the publication of the
accessing web services in the OntoWeaver-S generated service results. The following code shows the simplified
data-intensive web sites. As illustrated in figure 5, the JSP code generated from the definition of the data
process of accessing web services comprises the component example, which publishes results of the
following steps: service find-flights. Please note that the sign of “<%” and
(1) An end user opens the web page find-flights-page, “%” indicates that the wrapped code is server-side code,
enters his or her requirements for finding flights and which is executed by web servers at run time.
submits the input information to the web site.
(2) The OntoWeaver-S Service Integrator investigates
page making a request for accessing the specified
web service, and gathers information from the input
specified web service. <% //Part II: adding input roles for the specified task
(3) The OntoWeaver-S Service Integrator calls the IRS-II function_find_flights.addInputRole("from-place",
request.getParameter("kacomponent/from-place/input");
Server [17] to achieve the specified task find-flights function_find_flights.addInputRole("to-place",
augmented with the given constraints. request.getParameter("kacomponent/to-place/input");
(4) The IRS-II Server invokes the corresponding web ……
// Part III: achieving the specified task
service. function_find_flights.achieveTask(); %>
presentation modelling [11, 2, 21, 5, 13, 7]. However, as
<%while (function_find_flights.hasNextResultOutput()) already pointed out, these frameworks do not provide
{ %> means to support access to web services. As a
<%=function_find_flights.get(“airline”) %>
consequence, they limit the functionalities of the target
<%=function_find_flights.get(“fromairport”) %>
web applications to the management of back-end data
……
sources. WebML [5, 3] and OntoWebber [13] are the
<% }%> closest approaches to OntoWeaver-S.
OntoWebber defines explicit site models to abstract
The code comprises four parts: i) the first part data-intensive web sites, and uses ontologies as the
instantiates a service integrator using the specified task foundation for web application design. It supports the
name and the task ontology name according to the access to distributed heterogeneous data sources for the
specification of the associated semantic web service; ii) target web applications by providing wrappers and
the second part gathers input information from the translators to process data sources in different formats.
corresponding input elements and passes the information However, OntoWebber does not support the integration of
to the corresponding input roles, according to the (semantic) web services into web applications.
specification of the corresponding knowledge acquisition WebML [5] relies on explicit site models to enable the
component; iii) the third part achieves the specified task design and development of data-intensive web
by calling the IRS-II Server; and iv) the fourth part applications. However, in comparison with OntoWeaver,
presents the service results in a table repeatedly. the composition model, which provides means to enable
As mentioned earlier, OntoWeaver-S provides a tool the composition of user interfaces for web pages, is not
called Service Integrator to integrate semantic web expressive enough to enable the composition of complex
services into web sites. The following Java code shows user interface as it does not provide constructs to model
how the Service Integrator achieves this goal. First, it atomic user interface elements. Brambillla et al. [3] have
calls the function achieveTask() from the IRS-II Server, recently extended WebML by means of a set of web
augmenting the specified task name, task ontology name, service hypertext primitives for communicating with web
and the values for the input roles. The result of this services. However, as already emphasised, they fail to
function is written in XML (this has been indicated by the integrate web services into the WebML design
semantic description of this web service). The framework; they simply treat them as functionalities,
OntoWeaver-S Service Integration then gets the result which can be invoked, much like any other web
from the IRS-II Server and processes the result, and application.
makes it ready for the presentation.
public void achieveTask()
{
6. Conclusions
String serviceResult = this.irsServer.achieveTask(this.taskName,
this.taskOntologyName, This paper has shown how we have augmented
this.InputRoles);
this.processingResultOutputs(serviceResult); OntoWeaver, a data-driven web design framework, to
} produce OntoWeaver-S, a semantic service driven
//processing results and making it ready for publication
framework, which supports rapid prototyping of web
private void processResultOutputs(String serviceResult) service centred data-intensive web sites. OntoWeaver-S is
{ integrated with a comprehensive platform, IRS-II [17] for
ResultOutputReader reader=new ResultOutputReader(
serviceResult); the specification, discovery, and execution of semantic
this.resultOutputList=reader.getResultOutputList(); web services. Moreover, OntoWeaver-S provides a set of
}
user interface constructs to support the modelling of the
public boolean hasNextResult() typical user interfaces of service centred data-intensive
{
boolean hasNext= this.resultOutputList.hasNext(); web sites, including information visualization, which
if (hasNext) allows the visualization of dynamic data content coming
this.currentRowResult= this.resultOutputList.next(); from the underlying databases or remote web services,
return hasNext;
} and information provision, which allows the provision of
//getting the value of the specified result field of the current row information for updating or querying the back-end domain
public String get(String outputName)
{ data sources or for invoking remote web services.
return this.currentRowResult.get(outputName); Tools have been implemented to support service
}
centred data-intensive web sites at design time as well as
at run time. In particular, a Site Designer has been
5. Related Work implemented to offer graphic user interfaces to allow the
design of data-intensive web sites; and the Service
Modelling approaches to web site design typically Integrator has been prototyped to provide support for the
approach the design of web applications at three levels: integration of web services into data-intensive web sites at
domain modelling, navigation modelling, and run time.
To our knowledge OntoWeaver-S is the first toolkit
that attempts to integrate (semantic) web services into a [11] T. Isakowitz, E.A. Stohr, and P. Balasubramaninan, RMM:
high level design framework. In the future, we will focus A Methodology for Structured Hypermedia Design,
on defining constraints validating the complex site Communications of the ACM, August 1995.
[12] Java Web Services Developer Pack, available online at
specifications and provide tools helping developers to find
http://java.sun.com/webservices/webservicespack.ht
and correct the specifications that are either with errors or
ml.
being inconsistent in the entire site model. [13] Y. Jin, S. Decker, and G. Wiederhold, OntoWebber:
Model-Driven Ontology-Based Web Site Management,
References Semantic Web Workshop, Stanford, California, July 2001.
[14] Y. Lei, E. Motta, and J. Domingue, An Ontology-Driven
[1] A. Ankolekar, M. Burstein, J. Hobbs, O. Lassila, D. Martin, Approach to Web Site Generation and Maintenance, in
D. McDermott, S. McIlraith, S. Narayanan, M. Paolucci, T. proceedings of 13th International Conference on
Payne, and K. Sycara, DAML-S: Web Service Description Knowledge Engineering and Management, Sigüenza, Spain
for the Semantic Web, in Proceedings of the 1st 1-4 October 2002, pp. 219-234.
International Semantic Web Conference (ISWC 2002). [15] Y. Lei, E. Motta, and J. Domingue, Design of Customized
[2] P. Atzeni, G. Mecca, and P. Merialdo, Design and Web Applications with OntoWeaver, in proceedings of the
Maintenance of Data-Intensive Web Sites, in proceeding of International Conference on Knowledge Capture, Florida,
the 6th int. Conference on Extending Database Technology October, 2003.
(EDBT), Valencia, Spain, March 1998. [16] Y. Lei, E. Motta, and J. Domingue, Modelling Data-
[3] M. Brambilla, S. Ceri, S. Comai, and P. Fraternali, Model- Intensive Web Sites with OntoWeaver, accepted in
driven Development of Web Services and Hypertext International Workshop on
Applications, SCI2003, Orlando, Florida, July 2003. Web Information Systems Modelling (WISM 2004), Riga,
[4] S. Ceri, P. Fraternali, and S. Paraboschi, Design Principles Latvia, 2004.
for Data-Intensive Web sites, SIGMOD Record, 24(1), [17] E. Motta, J. Domingue, L. Cabral, and M. Gaspari, IRS-II:
March 1999. A Framework and Infrastructure for Semantic Web
[5] S. Ceri, P. Fratenali, and A. Bongio, Web Modelling Services, in Proceedings of the 2nd International Semantic
Language (WebML): A Modelling Language for Designing Web Conference 2003 ( ISWC 2003), 20-23 October 2003,
Web Sites, WWW9 Conference, Amsterdam, May 2000. Sundial Resort, Sanibel Island, Florida, USA.
[6] D. Fensel and C. Bussler (2002), the Web Service [18] Resource Description Framework (RDF) Model and
Modeling Framework WSMF, available online at Syntax, W3C Proposed Recommendation.
http://informatik.uibk.ac.at/users/c70385/wese/wsmf.bis200 http://www.w3.org/TR/PR-rdf-syntax/.
2.pdf. [19] Resource Description Framework (RDF) Schema
[7] F. Frasincar, G. Houben, and R. Vdovjak, Specification Specification 1.0, W3C Candidate Recommendation.
Framework for Engineering Adaptive Web Applications, in http://www.w3.org/TR/rdf-schema/.
the Eleventh International World Wide Web Conference [20] W. Retschitzegger, W. Schwinger, Towards Modelling of
WWW2002 Web Engineering Track. DataWeb Applications - A Requirement's Perspective,
[8] P. Fraternali, Tools and Approaches for Developing Data- Proc. of the Americas Conference on Information Systems
Intensive Web Applications: a survey, ACM Computing (AMCIS) Long Beach California, Vol. I, August 2000.
Surveys, Sept. 1999. [21] D. Schwabe and G. Rossi, The Object Oriented
[9] F. Garzotto, P. Paolini, and D. Schwabe, HDM—A Model- Hypermedia Design Model, Comm. Of the ACM, Vol.38,
Based Approach to Hypertext Application design, ACM #8, pp 45-46, August 1995.
Trans. Inf. Syst. 11, 1 (Jan. 1993), pp. 1 – 26. [22] Simple Object Access Protocol (SOAP) (2000). W3C Note
[10] IBM Web Services Toolkit – A Showcase for Emerging 08. Available online at http://www.w3.org/TR/SOAP/.
Web Services Technologies, available online at [23] UDDI Specification, available online at
http://www- http://www.uddi.org/specification.html.
3.ibm.com/software/solutions/webservices/wstk-info.html. [24] Web Services Description Language (WSDL) (2001), W3C
Note 15, available online at http://www.w3.org/TR/wsdl.