The remaining of the paper is organized as follows. In
Section 2, we briefly present necessary technology to allow
the reuse of the functionalities. In section 3 we expose our
approach which consists of the proposal of the e-Learning
Web services; thus a generic description of the e-learning Web
services and the architecture to show the process of
publication, discovery and reuse of the functionalities is also
presented. Section 4 illustrates the architecture design .Finally;
we give a conclusion and future work directions in section 5.
II. REUSABILITY VIA WEB SERVICES : OVERVIEW
To reduce the cost and lighten the development of the elearning
systems, the issues of reusability and interoperability
in this domain needed to be tackled.
A. Web services
The technology of Web service has the ability to increase
the much needed interoperability and reusability of
educational components [7].A Web service is an application
component (program) put at the disposal to other systems
around the web. A Web service has methods that can be
invoked remotely using standard protocols (HTTP).The Web
services present the advantage to be independent from
platforms and reusable. A Web services is described by a
description WSDL (Web Service Description Language) with
the XML format which is recorded in UDDI registers
(Universal Description Discovery and Integration).Other
systems (Web services, applications...) communicate with the
Web services using SOAP messages, in the XML format,
transmitted with the HTTP protocol.
Web services include three elements:
• Requester: is an application that requires a service.
It initiates the location of the service in the directory,
interacts with the service across a protocol and
performs the function exposed by the service.
• Provider: is an addressable entity via a network, it
accepts and executes the requests coming from a
customer. The service provider publishes the service
contract in the directory so that it can be accessed by
the customers.
• Web services directory (UDDI): it is a directory
which contains the services available. It is an entity
which accepts and saves the contracts of the service
provider and presents these contracts to the
prospective clients.
Fig.1 shows the reference architecture of Web services [8].
Fig.1 Web services Architecture [8]
The fundamental technology for the discovery of Web
services is the register UDDI, intended to be used by the
human users. However the search in UDDI (comparison of the
request with the descriptions of the Web Services) is made
only for the syntactic level. This method presents some
limitations: the Syntactic search does not allow to find the
service asked every time; moreover, a software agent cannot
examine the textual description intended for the human ones,
it cannot distinguish between two different Web services with
the same syntactic description, it can have knowledge of the
syntactic structure of the description but not its semantics,
which presents a handicap for the automation of the discovery
of the Web services. To overcome this problem a new
generation of services, called semantic Web services, were
proposed.
B. SEMANTIC WEB SERVICES
The semantic Web services are the convergence of the
technology of Web services and semantic Web; these are Web
services with descriptions endowed with semantics. The
parameters of the Web service must be described so that a
software agent can have knowledge of their meaning. This is
realized by the definition of vocabularies organized in
ontology .In the domain of the Web services, the ontologies
are used to annotate semantically the descriptions of the
functionalities of the Web services [16]. Thus, for a software
agent can have knowledge of the semantics of a description of
a Web service, it just needs to access the ontology. Various
approaches were proposed among others ontology OWL-S.
Ontology OWL-S [9] consists of three main elements.
1) ServiceProfile : What does the service provide for
prospective clients? The response to this question is
given in the "profile" which is used to advertise the
service.
2) ServiceModel : How is it used? The response to this
question is given in the "process model". This
perspective is captured by the ServiceModel class.
3) ServiceGrounding : How does one interact with
it? The response to this question is given in the
"grounding". A grounding provides the necessary
concrete details related to message format, transport
protocol, etc.
In the following of this research paper, we illustrate our
proposed approach for the creation and the description of the elearning
Web services to allow the reuse of the functionalities
in the creation of the e-learning systems.
III. THE DEVELOPMENT AND REUSE OF THE ELEARNING
FUNCTIONALITIES
E-learning platforms and their functionalities resemble one
another to a large extent. The functionalities that span across
many e-Learning systems (common functionalities) can be
built as reusable components by using web services.