ABSTRACT

Computer science education is greatly affected the object-oriented paradigm. This can be seen in the numerous new teachers being attracted to programming languages, such as Java. Learning the object-oriented paradigm is however difficult for most novice students, mostly because  it requires a new way of thinking about computing and more depth to grasp. Thus, to promote the object-oriented paradigm at the introductory level, a re-examination of the teaching method  is needed. This article describes a new teaching approach  for rethinking  object-oriented programming  within the constructivist epistemology.

1.  INTRODUCTION

This article describes a new teaching approach to programming motivated by principles found in the constructivist epistemology. The need for developing a new teaching method arose when we realized that the predominant model of instruction  in computer science education - the objectivist model of  learning - was inadequate for  most students to learn  object-oriented concepts, because it does not engage the mind appropriately to successfully tackle the challenges of the object-oriented approach. Learning the object-oriented paradigm is indeed difficult for most  novice students, mostly because it is more abstract than the procedural approach. Moreover it requires new ways of thinking and more depth to grasp, particularly with regard to the analysis and design activities prior to program coding, and when the problems to be solved were different from those whose solution was explained previously. The constructivist view is more appropriate to deal with the pedagogical problems encountered in switching from the procedural approach to programming to the object-oriented paradigm, since it takes into account students' prior knowledge in programming and students' prior experiences in problem solving [4,5]. Moreover, constructivism offers a potentially powerful way to rethink the pedagogical practice at the introductory level by stressing the need for the learner to play an active role in constructing object-oriented knowledge.  Constructivism has been successfully implemented in mathematics and science education [8,9].  It can be adopted to our field with slight modifications.

The remainder of this article is organized as follows. In section 2 we give an overview of  the objectivist and the constructivist models of learning. In section 3 we reconceptualize object-oriented  knowledge within the constructivist epistemology. In section 4 we outline a constructivist approach for learning object-oriented programming at the introductory level. Finally, some remarks on further work conclude the article.

2. PARADIGMS OF LEARNING
2.1 The Objectivist Model of Learning

Basically, computer science education relies on the objectivist model of learning  which views learning as the passive transmission of knowledge from the teacher to the learner. This model does not suggest that students' prior knowledge, e.g. procedural programming, can affect current learning, e.g.  object-oriented concepts, since its metaphor of mind is that of a blank page, a tabula rasa, waiting to be filled with knowledge [9]. Clearly, the objectivist model of learning  does not engage the mind appropriately to go beyond inappropriate prior knowledge. The result is, even after one year of instruction, a lack of conceptual understanding, bad programming habits and serious misconceptions about object-oriented program development. Programming is understood as an art rather than a discipline with principles which guide the development of readable, modular, extensible, and reusable objects [7]. This situation is, to some extent, the result of passive learning: listening to lectures, reading textbooks, and doing programming  work without engaging the mind appropriately to successfully  tackle the object-oriented paradigm [5,7].
 
2.2 The Constructivist Model of Learning

In stark contrast to the objectivist view, the constructivist perspective regards learning less as the product of passive transmission than a process of active construction. Learning is an active process in which learners construct new knowledge based upon their prior knowledge. Consequently, a constructivist approach to learning needs to probe prior knowledge and evaluate whether it conflicts with the knowledge being taught. Similarly, a constructivist methodology needs to evaluate how the procedural model of programming conflicts with the object-oriented approach. If it does, new ways must be found of reconstructing the object-oriented concepts; otherwise there is no guarantee that the object-oriented approach will  be adopted. The constructivist perspective clearly diverges from the objectivist model of learning  which presumes that knowledge can be put directly into the learner's head. Interested readers should consult [1,3,5,6,7,8,9] for more details. There are basic principles for designing a constructivist learning strategy for object-oriented programming.

• Object-oriented concepts must be actively constructed by learners, not passively transmitted by teachers.
• The role of object-oriented concepts must be emphasised in problem solving.
• Students' prior knowledge must be evaluated to find out   wether it conflicts with the object-oriented approach.
• In order to be useful for problem solving, problem situations must be related to object-oriented concepts and to the object-oriented language being used, which must themselves be strongly related to each other.
• The process of constructing interrelated object-oriented knowledge requires  problem-solving skills.
• Traditional modes of  learning such as lectures should be replaced by a set of activities where the students are actively engaged in the concepts being constructed.
• To get students actively involved in problem solving, the activities must focus around a set of realistic, intrinsically motivating problems.

3. A CONSTRUCTIVIST VIEW OF OBJECT-ORIENTED KNOWLEDGE
3.1 Object-Oriented Knowledge Types

From a constructivist point of view, there are three strongly interrelated knowledge types which are relevant for the object-oriented approach:

• Object-oriented concepts, that is abstraction, encapsulation, inheritance, polymorphism, and dynamic binding. These concepts may be  used to understand problem situations, to design object-oriented models, and to choose appropriate means of implementation. Students must also learn to use object-oriented components within the WWW, by incorporating objects in a form that is reusable, concurrent, interactive, and distributed [2].
• Then, we need an object-oriented language for implementing object-oriented concepts.  Today,  Java  is the most popular object-oriented language. It includes powerful means of implementation, such as Java Development Kit (JDK), the WWW, visual application builder tools, as well as existing reusable components - JavaBeans - which can be adapted and extended to fit the requirements of new problems.
• Finally, we need a variety of problem situations from which we derive problem-specific knowledge - that is the relevant features and the requirements of the problem that can be expressed in terms of  object-oriented concepts.

Traditional teaching of object-oriented programming does not focus on building strong links between these knowledge types. However, from a constructivist point of view, these knowledge types need to be closely related to each other to be useful for problem solving. This means that problem situations must be closely linked to object-oriented concepts and to the object-oriented language constructs, which must themselves be closely linked to each other [3].

3.2 Skills for Constructing Object-Oriented Knowledge

The constructivist view asserts the construction of  interrelated  knowledge necessitates problem-solving skills. This is consistent with research and the practical experiences of expert software designers. Insights from software engineers indicate that designers focus on the overall structure of the software system, that is on the general functions of the parts and how they interrelate with each other to form the whole. Moreover, the analysis of the problem domain and the design of a conceptual model are more central to the development of software than the code. This means that building interrelated object-oriented knowledge requires thinking at a higher level than the code level, see [11]. Given this background, we can distinguish the following  categories of problem-solving skills:

• Analysis skills, such as understanding, describing, refining, and representing problem situations using object-oriented concepts.
• Design skills, such as modeling, integrating, reusing, and combining object-oriented components.
• Analogical thinking skills, such as recognizing similarities and differences between problem situations using object-oriented concepts.
• Reflexive, critical thinking skills, such as evaluating, explaining, and justifying the solution process.

Novice students use knowledge in different ways from experienced software designers. In contrast to experts, beginning students are usually not aware of the importance of problem-solving skills. They focus on programming issues rather than on the conceptual aspects [11].  In addition, students have a great deal of difficulty in solving new problems,  because they cannot use object-oriented concepts to identify similarities between problems they have already solved and the new problem they are currently trying to solve  [4,7].

4. A CONSTRUCTIVIST APPROACH TO OBJECT-ORIENTED PROGRAMMING

The goal of a constructivist approach to object-oriented programming is to help each student (a) to explore their prior knowledge about computing, (b) to refine their understanding of object-oriented concepts, (c) to use object-oriented concepts to analyse problem situations (d) to develop problem solving skills, (e) to solve new problems, and (e) to put together object-oriented knowledge into an integrated unity.

4.1 Characteristics of Activities

To be successful, a teaching method motivated by constructivism needs to be organized around a set of activities where students are actively engaged in the knowledge being learned. Each activity includes four integrated  parts:

• Firstly, the activity must rely on a realistic, intrinsically interesting problem situation that motivates the students to construct object-oriented knowledge, including specific questions that probe students' understanding.
• Secondly, the activity must refer to prior knowledge needed to do the activity, e.g. concepts, tools, and language constructs students should be familiar with.  Likewise, substantial attention should be devoted to students' misconceptions and programming practices that directly conflict with the object-oriented approach.
• Then, the activity must tell students the new object-oriented knowledge that will be raised and addressed during the activity, e.g. the concept of inheritance.
• The final step consists of reflecting on the solution process. This task is of primary importance for the learning process, since it helps the teacher to discover what and how the students have learned.
 
4.2 Examples of Activities

In this section we give an outline of some activities involving analysis, design, implementation, and evaluation processes.
 

• Design object-oriented models using existing solutions.  This activity is based on the idea that the solutions of past problems can be used to specify the requirements of a new problem. To be able to reuse existing solutions, students need analogical thinking skills to identify conceptually similar problems they have previously analysed. The solutions might be adapted, modified and extended to meet the problem requirements. Finally, the activity consists of designing an  object-oriented model on the basis of the information available.

• Explore the  class library for reusable code. This activity will allow the exploration of class libraries using object-oriented concepts. It is of primary importance for the implementation process. Java and similar languages provide sufficient flexibility to achieve this activity. Basically, objects in class libraries can be reused, and extended with slight modifications through inheritance. With reuse, students learn to incorporate existing software components - for example JavaBeans - , standard classes, and objects into the solutions of new problems. Existing code might be adapted and extended to fit new problems. To be efficient, reusable code should be stored so that it may be retrieved at any time.

• Study experts' design solutions. Students can learn most effectively from following design practices of expert software designers. Good examples of software design should include a study approach with experts' solutions and a summary of experts' thinking process. Students can then model their solutions on experts' thought processes using higher-order thinking skills. Likewise, substantial attention should be devoted to well-designed code, since it is extremely important for students to be able to read, modify, and extend good examples of well-structured, object-oriented code [11].

• Organize object-oriented knowledge in terms of similarities and differences. This activity will help students to structure  object-oriented knowledge by continually making connections between previously taught knowledge and new knowledge. For instance, to build connections between simple and distributed objects, we must look backward to what we have previously learned about simple objects. This is followed by looking forward in terms of developing distributed objects. This method allows us to organize  knowledge in terms of similarities and differences. Object-oriented concepts, models, or programs are compared («How are they alike?»), contrasted (« How are they different?»), and then reorganized to form conceptually similar or different knowledge structures.

• Develop alternative solutions. To increase the number of connections between  object-oriented concepts and a variety of problem situations, it is important to use the concepts in different contexts. One way to do this is to develop multiple valid solutions for the same problem, for example solutions based on simple, distributed, and concurrent objects. By solving problems in more than one way, students learn to use object-oriented knowledge in different ways which enhances the links between solutions, problems, and concepts.

• Reflect on the solution process. Most students do not have the skills needed to reflect on what they are doing. Usually, they focus on the product rather than on the solution process. They conceive a solution is just a program that works for them, rather than a program that is readable for others, modular, and extensible [8]. This activity helps students to reflect their solutions by relating  object-oriented concepts to the problem situation they have studied. Therefore, students should be asked questions that probe for understanding of the concepts underlying the problems' solutions. This task will allow them to discover their own misconceptions about programming and to correct them. It is clearly evident that without reflection, students will be unwilling to abandon their design and programming practices based on misconceptions, see [7].

 5. CONCLUSION

In this article, we have presented a new teaching approach to programming motivated by principles found in the constructivist epistemology. We have come to this approach as we realized that the predominant model of instruction - the objectivist model of learning - was inadequate to successfully tackle the pedagogical problems encountered in switching from the procedural approach to  the object-oriented paradigm. Although we have only been able to outline the new approach in broader terms, we are convinced that constructivism offers - by defining learning as an active process of construction - a potentially powerful way to rethink the pedagogical practice in computer science. We are now in the process of implementing the new approach by introducing constructivist ideas step by step. Developing a complete teaching strategy requires a long-term effort in several directions: we need to improve our understanding of students' prior knowledge, refine the program of activities, explore higher-order cognitive skills, develop better assessment and evaluation procedures, as well as material and teaching aids to support constructivist learning in computer science. 

REFERENCES

[1] Ben-Ari, M. Constructivism in Computer Science. Proceedings of the 29th SIGCSE Technical Symposium on Computer Science Education, March 1998, 257-261.
[2] Berg, D.J., and Fritzinger, J.S. Advanced Techniques for Java Developers, John Wiley & Sons, New York 1998.
[3] Floyd, C., et al. (eds.). Software Development and Reality Construction, Springer-Verlag, 1992, 86-100.
[4] Hadjerrouit, S. Teaching Java as First Programming Language: A Critical Evaluation. SIGCSE Bulletin, Volume 30, Number 2, June 1998, 43-47.
[5] Hadjerrouit. S. A Constructivist Approach for Integrating the Java Paradigm into the Undergraduate Curriculum. Proceedings of the 3th Annual Conference on ITiCSE, August 1998, 105-107.
[6] Kafai, Y., and Resnick, M. (eds.). Constructionism in Practice: Designing, Thinking, and Learning in a Digital World, Lawrence Erlbaum Associates, New Jersey, 1996.
[7] Mereno-Seco, F., and Forcada, M.L. Learning Compiler Design as Research Activity. Computer Science Education 7, 73-98, 1996.
[8] Phye, G..D. (ed.). Handbook of Academic Learning: Construction of Knowledge, Academic Press, London 1997.
[9] Steffe, L.P., and Gale, J. (eds.). Constructivism in Education, Lawrence Erlbaum Associates, New Jersey 1995.
[10] Sims-Knight, J.E., and Upchurch, R.L. Teaching Object-Oriented Design Without Programming: A Progress Report. Computer Science Education 4, 135-156, 1993.
[11] Tewari, R., and Friedman, F. L. A Framework for Incorporating Object-Oriented Software Engineering in the Undergraduate Curriculum. Computer Science Education 4, 45-62, 1993.
 
 

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 

 
 
 
 
  [13] Spivey, N. N. The Constructivist Metaphor: Reading, Writing, and the Making of Meaning, Academic Press, London 1997.
 
  [7] Hadjerrouit, S. Educational Impacts of the New Paradigm of Informatics.Proceedings of the Norwegian Annual Conference on Computer Science, Tapir 1998, pp. 185-194.
 
 
  [3] Brauer, W. The New Paradigm of Informatics in: Mauer (ed.). New Results and New Trends in Computer Science, Springer-Verlag, 1991, 15-24.
 
  The result is, even after one year of instruction, a lack of conceptual understanding of the object-oriented paradigm and serious misconceptions about object-oriented program development. Programming is understood as an art rather than a discipline with principles which guide the development of readable, modular, extensible, and reusable objects [8]
 
 
 

To be useful for problem solving, these types of knowledge need to be closely related to each other. This means that object-oriented concepts, object-oriented language constructs, and object-oriented problem requirements must be integrated to interrelated  knowledge  which can be retrieved at any time [3].

Keywords
Constructivism, Java, object-oriented programming
 

 
  including some suggestions as to how it can be constructed using higher-order thinking skills. This is the main activity.
 
  The goal of a constructivist approach to object-oriented programming is to help each student to construct interrelated knowledge  that can be used for efficient problem solving. When knowledge is structured, the conceptual understanding of problems is enhanced, design and implementation ability improves, because object-oriented concepts may be used to understand problem situations, to design conceptual models, and to choose appropriate means of implementation. To be successful, a pedagogical approach motivated by constructivism needs to be organized around a set of activities where students are actively engaged in the knowledge being learned.
 
 
 
 
 
  The goal of the activities is to motivate the students to construct  interrelated, object-oriented knowledge  in the course of problem solving
 
   These activities are important for improving the ability to construct interrelated object-oriented knowledge.