CONTENTS AND METHODOLOGY OF MIDDLEWARE
PROGRAMMING FOR DISTANCE LEARNING
IN MASTER PROGRAMS
Felipe Garcia-Sanchez, Antonio-Javier Garcia-Sanchez and Joan Garcia-Haro
Department of Information Technologies and Communications, Technical University of Cartagena
Campus Muralla del Mar, Cartagena, Spain
Keywords: Distributed Programming, Distance Learning, Master Program.
Abstract: This paper deals with a well-known problem, the learning of distributed programming languages, especially
when they are included in distance programs. In particular, the course is focused on middleware learning in
a master program, in which students that access to it have heterogeneous programming level and skills.
Therefore, a real scenario and a real case study are presented, where students must rationalize their effort.
An emphasis is placed on those students that offer more weaknesses. Moreover, this paper presents the
students evaluation process, and summarizes the results obtained after the course had been developed.
1 INTRODUCTION
Learning in the field of Object Oriented
Programming (distributed OOP) and, in particular,
learning middleware, is a well-known issue in
software teaching. It gets worse when students face
distributed OOP for the first time or when the course
is included in a postgraduate degree where students
come from different study programs. Sometimes,
their degrees do not include subjects typical of
traditional Computer Science Degree in their courses
syllabus. Therefore, some of the contents and
methodology of traditional courses for graduate
degrees must be reviewed.
Knowledge of middleware technologies is
commonly required by different market employees.
Therefore, these related topics must be included in
the program for Computer Science degrees,
including master ones.
This document describes and emphasizes the
contents and methodology followed to develop an
intensive course of distributed programming
systems, in particular regarding middleware, and it is
oriented for distance learning. The motivation is to
include this course in a professional master program
where students normally have strict working
schedules in their respective companies. In this
paper, the experiences and the results achieved are
presented and discussed.
The main objectives for the course are to
advance in the knowledge of the programming
issues and to provide an appropriate background for
the students so that they can face their own
professional tasks. Specifically, the goals are: (a) to
get a good and sufficient knowledge for
understanding and applying the working
technologies, (b) to select the most appropriate
technology for a particular problem, (c) to establish
the requirements for adapting a given solution, (d) to
develop applications and distributed systems using
these technologies, and (e) to analyze and evaluate
the application performance.
In this paper, we detail the learning for two main
technologies (although the program includes
additional topics), namely: the general-purpose
middleware CORBA (Common Object Request
Distributed Architecture) (Bose et al., 2001) and the
commercial system based on .NET communications.
On the one hand, CORBA is general-purpose,
commonly free or non-licensed distributions are
provided and it is open-platform (not limited to any
operating system). On the other hand, the .NET
technology is commercial, owned by Microsoft
Company and operates over its operating system, the
Windows family.
The course consists of 3 ECTS (European Credit
Transmission System) (Dir.-Gen. Education, 2004)
and the students are required to have basic
programming knowledge. It is assumed that they
230
Garcia-Sanchez F., Garcia-Sanchez A. and Garcia-Haro J. (2009).
CONTENTS AND METHODOLOGY OF MIDDLEWARE PROGRAMMING FOR DISTANCE LEARNING IN MASTER PROGRAMS.
In Proceedings of the First International Conference on Computer Supported Education, pages 230-234
DOI: 10.5220/0001976702300234
Copyright
c
 SciTePress

were instructed in the common programming
language, Java (Bose et al., 2001), and they are thus,
familiarized with objects and classes. Technology
degrees required to access the master course should
include it; however, the master program includes a
previous levelling course for those students with low
skills in any discipline as programming in our case.
CORBA learning is developed on Java programming
language. However, as .NET does not include any
interface for it, the course includes learning in C#
language.
Material accessible on-line is available for
students. In particular, slides, class notes, exercises
and referenced books for theoretical concepts, and
pieces of developed software (complete and partial
solutions for diverse cases of study) for practical
experiences. In fact, students have unlimited open
access to a computer room where they may develop
their own solutions. In it, computers have installed
Java programming environments as NetBeans
(Boudreau et al., 2003) and Eclipse (Pluta, 2003)
and the .NET one, the Microsoft Visual Studio
(Petzold, 2002).
The rest of the paper is organized as follows:
section 2 outlines previous work on this topic,
section 3 defines and details the contents included in
the course, section 4 shows the methodology
employed for distance learning, leaving section 5 for
concluding and showing the results obtained for
students.
2 PREVIOUS WORK
As far as the authors know, a recent paper
summarizing contents and methodology included in
a middleware course can not be found. The closest
one may be the Brownsmith (Brownsmith, 2007)
where the topics included in a middleware course
are detailed. It is aimed at offering a critical insight
in order to be able to select the right commercial
middleware for determinate professional tasks.
Following the same idea, many universities,
postgraduate institutions, academies, etc. offer a
wide range of courses in middleware. They may be
oriented for enterprise solutions and focused on a
particular or proprietary option. When the course is
aimed for a general-purpose technology, an existing
middleware is selected and the course is entirely
devoted to it. This paper presents the contents for an
integrated course where the most representative
technologies are chosen and developed.
3 CONTENTS INCLUDED IN THE
MASTER PROGRAM
3.1 CORBA Middleware
CORBA teaching is always a complex task. The
density, tools, options, and possibilities that this
technology offers cannot possibly be developed in a
single course assigning 1 ECTS to it. For this reason,
the main objective is to provide the basic
knowledge, management and development. Contents
are categorized into three types of concepts:
Basic Concepts: Middleware definition.
Heterogeneity. Extensibility. Security. Scalability.
Failure Management. Concurrency. Transparency.
ORB (Object Request Broker) Architecture.
Invocation System. The IIOP (Interface Inter-ORB
Protocol). The Object Definition Language IDL
(Interface Description Language). Application
Programming.
Applied Concepts: Remote Invocation Handle.
ORB Handle. Input and Output Options.
Compilation and Execution. Implementation and
Invocation Types. Service Implementation. Client
Implementation, etc.
Divulging Concepts: CORBA Programming
Environment. CORBA Data Structure. Three-Band
Services. Collection Service. Concurrency Service.
Event Service. Notification Service. Name Service.
Trade Service. Time Service, etc.
All topics have not the same relevance, as it
depends on their difficulty and the desired learning
level. For instance, the ORB invocation system is
retaken in different lessons, at the beginning of
them. The enumerated CORBA services are just
commented or referenced because only the Name
Service is used by the students for the practical
exercises. As for basic concepts, students must
understand the difference between using CORBA
and using a common client-server system and its
invocation model. They have a first topic about the
motivation to use an invocation system of objects
and to develop a distributed system. In particular,
they know the competitive advantages that CORBA
offers with respect to other solutions: its capability
as “global communicator” for different systems,
languages and application environments. For this
reason, students develop a communication between a
client and an object or service placed in a remote
server. Concepts as stub, skeleton POA (Portable
Object Adapter) or the IDL definitions are used for
this purpose.
As for the applied contents, most of them are
used for emphasizing the basic contents previously
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introduced. However, students improve from a
simple application such as “HelloWorld” to the
implementation of complex IDL’s, including
generation of own types, input-output attributes, etc.
The master timetable allows for a fast evolution.
Finally, the divulging contents are referred to
in just one lecture, with several working examples.
Their detailed architecture is not considered,
although students know their applications, especially
the most commonly ones used. In particular, the
Event, Notification and Trade Services are related to
different systems as peer-to-peer, brokering, etc.
3.2 .NET Architecture
In comparison to CORBA, the .NET platform has a
more commercial orientation. Regarding the Internet
Services field, business-to-business (b2b) or
business-to-client (b2c) are examples of what
providers have offered to users in recent years. The
objective of the .NET platform is to give a solution
to Internet Services, developing communications
and applications easily.
.NET is the middleware solution offered by
Microsoft for developing distributed applications
among servers or servers and clients. Many concepts
and contents previously mentioned in the CORBA
subsections must be also applied here, and they are
not explained again. However, .NET does not only
allow communication and information transmission.
It also integrates applications with other oldest
platforms as DCOM, for upgrading the knowledge
of old programmers to b2c or b2b services.
Therefore, the students’ qualification has three
main objectives. First, they need to understand the
.NET architecture. .NET offers different possibilities
that must be known (ADO.NET, ASP.NET, Windows
Form, Web Forms, etc.) and the CLR management
(Common Language Runtime) for designing more
efficient applications. Secondly, students develop
interfaces or client applications. It is the base for the
b2b and b2c services. Thirdly, students work on
interfaces for transparent user access.
These three main goals involve different
concepts and competences that students must
acquire. The students have class notes, tutorship
sessions and referenced books for their learning or
search. Moreover, they perform intensification
assignments about topics proposed by the lecturer
and related to the three following parts:
.NET Architecture. Students must know the
relevance of the .NET platform previously to
develop their applications. Several questions arise
and have to be answered: What are the compatible
devices? What is the description language? What are
the developing tools? What are the service types
designed? What is the server for executing the
services? Etc. All of them are requirements for
learning this technology.
Applications and Service Development. The main
.NET objective is the development of web services
(ASP.NET) or databases (ADO.NET) and the design
of applications for interconnecting enterprises.
Therefore, the first main topic is the standard
definition for information interchange; and the
protocols XML, WDSL, UDDI and SOAP have to
be introduced.
Due to the heterogeneity of the programming
language provided by .NET platform, C# is chosen
as the language used during this course. The reason
for this is that many libraries and examples are
written in this language and it is the most similar to
Java, that was employed in the CORBA section.
Students learn concepts in C# such as classes,
objects, arrays, polymorphism, inheritance, etc. and
they also extend their knowledge about other
interesting concepts such as work cycle, the garbage
collector, etc. The lecturers remark the main
differences between C# and other languages, mainly
Java and C++. The material provided allows
students to know and search for any particular topic
that they require about this language. At the end of
the course, students recognize all the abilities
provided by Microsoft for communications among
enterprises and clients.
Information Transmission. .NET offers different
solutions for the communication among servers and
clients, ranging from simple classes for developing
sockets (simplest communication way) to most
advanced mechanisms such as .NET Remoting
(Conger, 2003) (Rammer 2002). In particular, the
latter permits the distributed communication
supporting different options.
4 METHODOLOGY FOR
DISTANCE LEARNING
4.1 CORBA Learning
As mentioned in the contents section, CORBA
teaching is a difficult task. As it is the case with
most programming learning, the best way to
approach it is to try to resolve problems at different
levels of complexity. However, distance learning
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and the limited access to the lecturer creates a
particular scenario to this main idea.
In this case, the first task is the explanation of
already resolved examples for the basic concepts
mentioned in the previous section. They are shared
among students, and the concepts are related to
client-remote service applications. When a particular
concept is studied, its associated code is emphasized.
The complete comprehension of these concepts
is particularly critical. CORBA is very sensitive to
code failures due to its different component
coordination. A small programming error will be
reproduced in several compilation and execution
failures. This problem makes students become
discouraged. They must face their problems alone
when they have enough knowledge to do it. Before
this, students solve the simplest exercises with a set
of usual failures that they may look up. This makes
them fluent enough in programming, gradually
improving until their own exercises resolution.
When the basic concepts are fixed, the most
advanced ones are introduced. They are first
introduced theoretically by referenced books,
prepared class notes and resolved questions.
Practical exercises are included too, getting more
relevant (in length and difficulty) when the course
approaching its end.
Both theory and practice imply different tasks. In
the theoretical part, students have a range of well-
known exercises, such as the “HelloWorld”, a basic
calculator, etc. The goal is for students to become
familiar with the CORBA architecture. On these
same cases, students have suggested improvements
that they may conduct. Usually these improvements
are simple and students may resolve them
throughout the course. Students get confidence and
lose the “fear” of this environment. They do not
have to resolve any exercise from beginning to end
at this level, since it could result in the students
giving up.
In the practical part, students face small
problems, using the material provided or searching
for it. The lecturer does not have an important
presence, and his mission is to make sure that all
students achieve the desired knowledge level.
In a second level, students have more experience
(even the heterogeneity of the group may cause
some of them to even consider the first level easy).
They implement more complex cases as a simple
database, where the lecturer “presence” is more
active. Doubts arise when they implement the
different topics assigned.
Regarding the second level of practical exercises,
students develop an introductory first practice where
CORBA and its invocation system are presented.
They compare a simple client-remote server
CORBA application with an also simple sockets one
(based on the communications interface included in
the operating system). Students learn the code,
compile it and execute it. Thereby, they know what a
middleware means. Moreover, they learn other key
issues, such as a benchmarking tool to analyze
applications.
The second practice is slightly more complex.
They perform a three-band communication. The
central server is an application that reads data from a
remote database, (which may be referred to by any
service). Client application refers to the remote
server for getting information from that database.
Students learn more realistic cases, and they face
new problems such as the concurrency one. The
lecturer must follow the students progress.
Finally, the tutorship has special relevance along
the course. Students with low background require a
special dedication. More examples and cases are
prepared for them. On the other hand, the most
advanced students do not employ many hours.
However, their monitoring is also required for
ensuring the entire right comprehension.
4.2 .NET Learning
Once the students have acquired the theoretical
concepts of this technology, the practical training
sessions start, consisting of the development of
applications. The objective is to put the previous
competences into practice, acquiring new ones.
These applications form a set of activities which will
be reported in a document. Furthermore, they will be
managed by a lecturer in an open access laboratory,
in tutorship timetable, and via email.
The activities have an increasing difficulty, and so
that, they start with simple applications
programming. Students train with the development
tool provided by the .NET platform. Subsequently,
students implement codes based on the
communications among clients and servers. The
course program concludes with a .NET Remoting
and a simple b2b service using this communication
methodology.
The first activity introduces students to the Visual
Studio environment which is provided by Microsoft.
All codes are implemented in C# language and the
objective is to develop .NET applications. In this
first activity, students perform the simulation of
banking transactions, so actions as balance enquiry,
expenditure, deposit, etc. are implemented. To this
aim, concepts like classes, objects, arrays,
CONTENTS AND METHODOLOGY OF MIDDLEWARE PROGRAMMING FOR DISTANCE LEARNING IN
MASTER PROGRAMS
233

inheritance, etc. are handled. This activity allows
students to apply methods and functions learnt in
theory lectures.
The second activity introduces students to the
graphical interfaces, in Windows Forms of the .NET
platform. It proposes developing an application that
allows to start with visual objects (buttons, boxes,
commands, etc.). For facilitating its programming,
the exercise is divided into two parts: (i) students
develop the code which allows to open an image file
in a particular format (bmp, gif, jpeg or tiff) and (ii)
the file opened in the previous format is converted
into another format type. The objective is twofold.
First, to acquire the knowledge of the components,
objects and classes which are necessary for carrying
out a graphical application. Secondly, students
acquire the competences for searching in the help
menus that Visual Studio .NET provides to them.
The third activity is based on the client-server
communication. The purpose is to develop a visual
environment and the same functionalities as the
well-known “Messenger” application. Two users
(irregardless of where they are placed) may
communicate with each other. To carry out this goal,
the lecturer identifies which objects are the most
suitable and he shows the students the different
methods and arguments that they may use for
implementing the “Messenger” application. From
this instruction and the .NET help, students program
the code for the peer communication, performing
sessions among users (via multicast) and
implementing an appealing graphical interface.
Finally, students check their programs in the
laboratory (Microsoft Visual Studio and libraries are
available), testing the code, correcting and
improving it.
The last activity is the implementation of a remote
application using the .NET Remoting library. It
consists of creating a database where the user adds
data in the fields implemented by students. These
fields are stored in an object placed in a remote
computer. Students develop the functions and
methods for performing the query action in a local
computer and the transmission of these queries to
the remote computer. It returns the result of the
search requested by the user. The lecturer trains
students to gain all the necessary competences for
doing this activity through traditional lectures and
bibliography. In particular, students gain experience
in the functions and methods that allows to
implement a distributed communication via .NET
Remoting. Furthermore, students apply the concepts
learnt related to the XML and SOAP protocol.
5 CONCLUSIONS
In this paper, the authors have presented the
concepts and methodology applied to the teaching of
the distributed objects programming and middleware
in a postgraduate master for Computer Science. The
contents are standard in relation to specific
middleware, but with two particularities: (i) it
highlights the practical implementation and (ii) it
offers a global vision to students, enabling them to
easily resolve future problems based on these
technologies. As for the employed methodology, it is
limited due to the distance learning. Material and
references are carefully selected, providing an
appropriate scenario where students may found their
own requirements and improvements.
Finally, the course started in the recent academic
year of 2007/2008 with 30 students. Within this
period, two evaluation dates were given: June and
September 2008. In June, the marks were the
following: 53% of students passed the subject, 30%
got B marks, 7% obtained A and 10% of students
did not take the exam. In September: the only
student that took it passed the exam.
ACKNOWLEDGEMENTS
This paper has been supported by project grants
TEC2007-67966-01/TCM (CON-PARTE) and TIC-
TEC 07/02-0002 (PLEDAX) and it is also developed
in the “Programa de Ayudas a Grupos de Excelencia
de la Región de Murcia, de la Fundación Séneca,
Agencia de Ciencia y Tecnología de la RM”.
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