Semantic web services and its challenges

International Journal of Computer and Technology (IJCET), ISSN 0976 – 6367(Print),
International Journal of Computer Engineering
Engineering
ISSN 0976 – 6375(Online) Volume 1, Number 2, Sep - Oct (2010), © IAEME
and Technology (IJCET), ISSN 0976 – 6367(Print)
ISSN 0976 – 6375(Online) Volume 1 IJCET
Number 2, Sep - Oct (2010), pp. 26-37 ©IAEME
© IAEME, http://www.iaeme.com/ijcet.html

SEMANTIC WEB SERVICES AND ITS CHALLENGES
Ms. A. Suganthy
Assistant Professor
Department of Computer Science and Engineering
Perunthalaivar Kamarajar Institute of Engg. & Tech
Karaikal, E-mail:asugan@gmail.com

G.S.Sumithra
Karaikal, E-mail: teju_tiny@yahoo.co.in

J.Hindusha
Karaikal, E-mail:hindu.hindusha@gmail.com

A.Gayathri
Karaikal, E-mail: ggayathri.pkiet@gmail.com

S.Girija
Karaikal, E-mail:girija.siva89@gmail.com

ABSTRACT
Semantic web technology has drawn a considerable attention of the researchers in
the field of distributed information systems, artificial intelligence and so on. Researchers
are taking interest to make use of semantic web technology as a central component of
their software constructions.
This paper gives an overview of Semantic web and web services, semantic web
technologies, semantic web architecture, semantic web approaches and key challenges.
Keywords – Ontology; Semantic Web services; Web services

26

International Journal of Computer Engineering and Technology (IJCET), ISSN 0976 – 6367(Print),

I.INTRODUCTION
It is obvious in modern computing. Semantic web services shares the documents
across the heterogeneous and global networks. It is a cooperative convergence of the
semantic web and web services. Semantic web deals about ontologies, logic, inference
and software agents. Web services are an infrastructure for developing the distributed
applications. Semantic Web Services are web services which have been marked and
annotated with machine-interpretable semantic markup in the form of ontologies. One
definition is the augmentation of descriptions through semantic web annotations, to
facilitate the higher automation of service discovery, composition, invocation and
monitoring in an open, unregulated, and often chaotic environment. [10].
Section2 discusses about the web services and the semantic webs. Section3
describes the technologies used in semantic web services. Section4 and section 5 discuss
about semantic web architecture and approaches. Section 6 describe about semantic web
challenges.
II.WEB SERVICES AND SEMANTIC WEB
This section discusses about Web Services and architecture of Web Services.
1. Web Services
The term Web services describes a standardized way of integrating Web-based
applications using the XML, SOAP, WSDL and UDDI open standards over an Internet
protocol. XML is used to tag the data, SOAP is used to transfer the data, WSDL is used
for describing the services available and UDDI is used for listing what services are
available. Web services are used primarily as a means for businesses to communicate
with each other and with clients, Web services allows organizations to communicate data
without intimate knowledge of each other's IT systems behind the firewall [1].
Web services allow different applications from different sources to communicate
with each other without time-consuming custom coding, and because all communication
is in XML, Web services are not tied to any one operating system or programming
language. For example, Java can talk with Perl; Windows applications can talk with
UNIX applications. [1]

27


The figure1 shows the basic architecture of Web Services. As illustrated in figure
1, the major components in the Web service architecture are service provider, service
requester and service broker.
This Figure1 shows that service providers publish their service(s) with the registry
repository of a service broker. Then, a service requestor initiates a search for a service by
contacting the service broker and searching the registry repository for services that meet
specific search criteria.

Figure 1 Web service architecture
The broker returns a list of services along with details of the associated provider
for each service. Subsequently, the service requestor binds with a selected service
provider(s) based on the provided details of registry repository and consumes them. In the
mentioned scenario, there are series of standards and protocols which enable
communication, description, publication and discovery of Web services.[1]
2. Semantic Web
Semantic Web is a group of methods and technologies to allow machines to
understand the meaning or "semantics" of information on the World Wide Web. The
term was coined by World Wide Web Consortium (W3C) director Tim Berners-Lee.
According to the original vision, the availability of machine-readable metadata would
enable automated agents and other software to access the Web more intelligently. The
agents would be able to perform tasks automatically and locate related information on
behalf of the user.
Semantic web researchers have proposed to augment web services with a
semantic description of their functionality in order to facilitate their discovery and
integration. The combination of web services with semantic web technology is referred as
Semantic Web Services. [11]

28


While the term "Semantic Web" is not formally defined it is mainly used to
describe the model and technologies proposed by the W3C. These technologies include
the Resource Description Framework (RDF), a variety of data interchange formats (e.g.
RDF/XML-eXtensible Markup Language , N3, Turtle, N-Triples), and notations such as
RDF Schema (RDFS) and the Web Ontology Language (OWL), all of which are intended
to provide a formal description of concepts, terms, and relationships within a given
knowledge domain.
Many of the technologies proposed by the W3C already exist and are used in
various projects. The Semantic Web as a global vision, however, has remained largely
unrealized and its critics have questioned the feasibility of the approach.
The semantic web provides the ability to add semantics to web services. First we
have OWL and its predecessor DAML+OIL (Ontology Inference Layer), both of which
are XML languages for representing ontology’s in the web. These technologies are used
to build upon the existing web services technologies to create semantic web services. [2].

III. SEMANTIC WEB TECHNOLOGIES
Various technologies are used in Semantic Web Services. The major Semantic
Web Technologies that are described in this section are WSDL, OIL, SOAP, UDDI.
1. WSDL (Web Services Definition Language)
It is an XML based References language for describing web services.
• Interfaces to all publicly available functions
• Data types for all message requests and message responses Binding to the
transport protocol to be used
• Addresses for locating the specified services
2. SOAP (Simple Object Access Protocol)
It is a XML protocol web service communication and invocation.
The Simple Object Access Protocol (SOAP) is a lightweight, XML-based
protocol for exchanging information in a decentralized, distributed environment. SOAP
supports different styles of information exchange, including: Remote Procedure Call style
(RPC) and Message-oriented exchange. RPC style information exchange allows for
request-response processing, where an endpoint receives a procedure-oriented message

29


and replies with a correlated response message. Message-oriented information exchange
supports organizations and applications that need to exchange business or other types of
documents where a message is sent but the sender may not expect or wait for an
immediate response.
3. UDDI (Universal Description, Discovery, and Integration)
Universal Description, Discovery, and Integration (UDDI) registry is a collection
of information on all the registered Web services. It enables dynamically discovering
Web Services providers. UDDI is a free public registry - vendors publish their Web
services and consumers search for appropriate Web services. It has three components:
UDDI is relatively lightweight, and contains enough information to direct users to
Resources hosted outside of it. It uses XML to represent its contents.
4. OIL (Ontology Inference Layer)
OIL can be regarded as an ontology infrastructure for the Semantic web. It is
based on concepts developed in Description Logic (DL) and frame-based systems and is
compatible with RDFS.
IV.SEMANTIC WEB ARCHITECTURE
The architecture of semantic web is illustrated in the figure below:

Figure 2 Semantic web architecture

30


The first layer, URI and Unicode, follows the important features of the existing
WWW. Unicode is a standard of encoding international character sets and it allows that
all human languages can be used (written and read) on the web using one standardized
form. Uniform Resource Identifier (URI) is a string of a standardized form that allows to
uniquely identify resources (e.g., documents).
A subset of URI is Uniform Resource Locator (URL), which contains access
mechanism and a (network) location of a document - such as http://www.example.org/.
Another subset of URI is URN that allows to identify a resource without implying its
location and means of dereferencing it - an example is urn:isbn:0-123-45678-9. The
usage of URI is important for a distributed internet system as it provides understandable
identification of all resources. An international variant to URI is Internationalized
Resource Identifier (IRI) that allows usage of Unicode characters in identifier and for
which a mapping to URI is defined. In the rest of this text, whenever URI is used, IRI can
be used as well as a more general concept.
Extensible Markup Language (XML) layer with XML namespace and XML
schema definitions makes sure that there is a common syntax used in the semantic web.
XML is a general purpose markup language for documents containing structured
information. An XML document contains elements that can be nested and that may have
attributes and content. XML namespaces allows to specify different markup vocabularies
in one XML document. XML schema serves for expressing schema of a particular set of
XML documents.
A core data representation format for semantic web is Resource Description
Framework (RDF). RDF is a framework for representing information about resources in a
graph form. It was primarily intended for representing metadata about WWW resources,
such as the title, author, and modification date of a Web page, but it can be used for
storing any other data. It is based on triples subject-predicate-object that form graph of
data. All data in the semantic web use RDF as the primary representation language. The
normative syntax for serializing RDF is XML in the RDF/XML form. Formal semantics
of RDF is defined as well.
RDF itself serves as a description of a graph formed by triples. Anyone can define
vocabulary of terms used for more detailed description. To allow standardized description

31


of taxonomies and other ontological constructs, a RDF Schema (RDFS) was created
together with its formal semantics within RDF. RDFS can be used to describe taxonomies
of classes and properties and use them to create lightweight ontologies.
The OWL is a language derived from description logics, and offers more
constructs over RDFS. It is syntactically embedded into RDF, so like RDFS, it provides
additional standardized vocabulary. OWL comes in three species - OWL Lite for
taxonomies and simple constrains, OWL DL for full description logic support, and OWL
Full for maximum expressiveness and syntactic freedom of RDF. Since OWL is based on
description logic, it is not surprising that a formal semantics is defined for this language.
RDFS and OWL have semantics defined and this semantics can be used for
reasoning within ontologies and knowledge bases described using these languages. To
provide rules beyond the constructs available from these languages, rule languages are
being standardized for the semantic web as well. Two standards are emerging - RIF and
SWRL.
V.SEMANTIC WEB APPROACHES
Here we discuss about the Semantic Web approaches namely Annotation,
Composition, Privacy and Security.
1. Annotation
Annotation of web services is the fundamental concepts underlying semantic web
services. DAML-S and OWL-S has been the most popular representations of web service
ontology but they are not without flaws, competitors and possible improvements. [2]
2. Composition
The OWL-S proposal [7] describes composite services thus: “complex or
composite services are composed of multiple mode primitive services, and may require
an extended interaction or conversation between the requester and the set of services that
are being utilized.” The need for composing services comes from web services.
The BPEL4WS is one language which attempts to enable composition of web services
into executable processes.
In Semantic Web Services composition is performed automatically by the system
based only on declarative descriptions of the task and services.

32


3. Privacy and Security
Privacy and Security work has mostly taken the form of policy languages with
which to annotate services. Security information includes encryption and digital signature
information about how inputs /outputs will be passed and stored. It also includes
information about to where information may be sent and for what purpose.
Kagal et al. [5] describes policies for authorization and privacy for SWS which
“aims to provide security and policy annotations for OWL-S service descriptions”.
Denker et al. [3] proposes security ontologies to annotate web services with
security information and describes a prototype.
Tontietal. [15] compares three languages for policy representation: KaoS,Rei and
Ponder.
V. KEY CHALLENGES
The most probable achievements that the SWS research community is expected to
make by 2012, the potential of SWSs with respect to integration architectures and the
availability of real-world studies in which SWS- based integration architectures are used.
[ 3]
Since 2001, the number of publications devoted to SWSs is constantly growing.
Mcllraith et al. (2001) published one of the first scientific articles on SWSs. A Google
Scholar query for SWS-related articles in Six matches for the year 2001. For the years
2004 and 2005, Google Scholar lists 189 and 344 articles, respectively. In 2006 the query
results in 426 matches and in 2007 the query results in 458 publications.[10]
Figure 3 described the evolution of the web which consists largely of documents
for humans to read to a Semantic Web that includes data and information for computers
to manipulate.
The existing applications have been developed in academic contexts or research
projects funded by public institutions. Work on Semantic Web languages and standards
provide a set of metadata to be used, nor do they say anything about how metadata can be
obtained [ 3].
Semantic Web provides some languages that express information in a machine
processable format. This implies that we do still have more expectations from our

33


computers today; we would like to take more benefit from their processing power. This
idea is also one goal of the “Grand Challenges in the Evolution of Information Society”
[17].

Figure 3 Berners-Lee Semantic Web
The World Wide Web Consortium (W3C) who has been working intensively on
Semantic standards, has approved the Resource Definition Framework (RDF) and the
OWL Web Ontology Language (OWL) and hence provides a solid base to establish
enterprise semantic applications and has implied a significant leverage of the Semantic
Web from a research level to an industry standard for building next generation
applications.
Like other technologies, the interest in creating and developing the Semantic Web
is motivated by the opportunities it might bring: either it can solve old problems, or it can
solve old problem in a better way. Here, instead of enumerating all the opportunities
enabled by the Semantic Web, we focus our discussion on the following closely related
aspects: web-services, agent-based distributed computing, semantics-based web search
engines, and semantics-based digital libraries [13]. Only limited semantics can be derived
from the lexical or syntactic content of the web pages.

Several systems have been built to overcome these problems based on their idea
of annotating Web pages with special HTML tags to represent semantics, including
SHOE (Simple HTML Ontology Extensions) system.[8].

34


New opportunities impose new challenges. In the following, we focus our
discussion on the following challenges that we are facing now: the development of
ontologies, and the development of the formal semantics of Semantic Web languages,
and the development of trust and proof models.[13]. The goal of the SWS Challenge is to
develop a common understanding of various technologies intended to facilitate the
automation of mediation, choreography and discovery for Web Services using semantic
annotations. The intent of this challenge is to explore the trade-offs among existing
approaches. Typically, we only run one surprise problem at a workshop due to resource
restrictions, but there may be exceptions to this practice. The process is summarized in
the table 1.

Date/Time Phase Description
Committed participants will receive
"Code freeze"
(1) Deadline Day 0 instructions and credentials for the
credentials distribution
Phase 2.
"Code freeze" The deadline for existing solution
(2) Day 1
submission submissions.
Committed participants will gain
Surprise problem
(3) Day 2 access to the surprise problem
announcement
description.
Day 2 + n - depending The deadline for surprise problem
(4) Solution submission
upon the problem solution submissions.
The surprise problem solutions
(5) Next Day Solution verification
verification report.
Table 1: Surprise problem solution
A solution submission should be accompanied with a document clearly stating all
changes that were introduced to the frozen version in order to respond to the surprise
problem requirements. Further, we may ask at the workshop that participants dynamically
demonstrate the ability to make minor changes to the surprise problem and get the new
correct answer [15].
The overall objective of the challenge is to apply Semantic Web techniques in
building online end-user applications that integrate, combine and deduce information
needed to assist users in performing tasks. Intentionally, the challenge does not define
specific task, data set, application domain or technology to be used because the potential

35


applicability of the Semantic Web is very broad. Instead, a number of minimal criteria
have been defined which allow people to submit a broad range of applications.
VI. CONCLUSION
Semantic Web Service is an emerging technology for supporting distributed
computing in the environments like Internet. Research is going on to formulate a
standardized architecture for Semantic Web. And the Framework for describing the
Ontology is also not well defined. There are still many issues to be resolved. The
Semantic Web Technologies are all new and demands its own requirements.
VII. REFERENCES
1. Berners-Lee, T, Hendler, James and Miller, E (2002). Integrating Applications on the
Semantic Web," Journal of the Institute of Electrical Engineers of Japan, October,
2002.
2. Berners-Lee, Tim; James Hendler and Ora Lassila (May 17, 2001). "The Semantic
Web". Scientific American Magazine. Retrieved March 26, 2008.
3. Daniel Bachlechner,Kerstin Fink,”Semantic Web Service Research: Current
Challenges and Proximate Achievements”
4. David Brokenshire,Surrey BC V3T 5X3, “A Review of Semantic Web services”.
5. Denker. G., Kagal, L., Finin, T., Paolucci, M., and Sycara,K. security for DAML
Web services: Annotation and Matchmaking, Vol. 2870.Jan 2003.
6. Jagadeesh Nandigam, Venkat Ngidivada, Mrunalini Kalavala “Semantic Web
Services”
7. Kagal, L, Finin, T., Paolucci, M., Srinivasan,N.Sycara, K., and Denker,G.
authorization and Privacy for Semantic Web Services. Intelligent Systems, IEEE (see
also IEEE Intelligent Systems and their Applications) 19, 4 (2004).
8. Luke, S., Spector, L., Rager, D. & Hendler, J. (1997). "Ontology-based web agents".
In Proceedings of the 1st International Conference on Autonomous Agents, Marina
del Rey, California, pp. 59-68 New York, NY: ACM press.
9. Martin, D.,Paolucci, M.,Mcllraith, S.A.,Burstein, M,; McGuinness, D., Parsia, B.;
Payne, T., Sabou,M.;Solanki,M.,Srinivasan, N.,Sycara,K. (2004): Bringing

36


Semantics to Web Services: the OWL-S approach, Proceedings of the First
International Workshop on Semantic Web services and Web Process Composition.
10. Mcllraith, S.A., Son, T. C., Zeng,H. (2001):Semantic Web Services,IEEE
Intelligent Systems, 16(2),pp. 46-52.
11. Payne, T., and Lassila, O. Guest Editors Introduction: Semantic Web Services.
Intelligent Systems, IEEE (see also IEEE Intelligent Syatems and their
Applications) 17, 1 (2002),15 –17.
12. Sabou, Marta. Building Web Service Ontologies. The Dutch Graduate School For
information and Knowledge Systems
http://Kmi.open.ac.uk/people/marta/papers/thesis.pdf.
13. Shiyong Lu, Ming Dong and Farshad Fotouhi “The Semantic Web: opportunities
and challenges for next-generation Web applications”.
14. “Semantic Web Service Challenge: Evaluating Semantic Web Services Mediation,
Choreography and Discovery” , sponsored by STI International.
15. STAAB, S.,Van Der Aalst, W,Benjamins,V., Sheth,A., Miller,J., Bussler,C.,
Maedche,A Fensel,D., abd Gannon,D.Web services,been there, done that,
Intelligent Systems, IEEE (see also IEEE Intelligent Syatems and their
Applications) 17, 1 (2002),15 –17.
16.Tonti.G.,Bradshaw,J.M.,Jeffers,R.,Montanari,R.,Suri,N., and Uszok, A. Semantic
Web Languages for Policy Representation and Reasoning: A Comparison of KaoS,
Rei,and Ponder, vol. 2870. Jan. 2003.
17. Wolfgang Wahlster, “Grand Challenges in the Evolution of the Information
Society”, November 2004.
18. WWW.dcs.bbk.ac.uk/…/ervices/Architecture.gif.
19. WWW.Wikipedia.com

37

Semantic web services and its challenges

Recommended

More Related Content

What's hot (19)

Viewers also liked (20)

Similar to Semantic web services and its challenges (20)

More from iaemedu (20)

Semantic web services and its challenges