A Web-Based Application Development Course
for the Computing Curricula 2001/NC3 Track

T. Andrew Yang Computer Science Department University of Houston - Clear Lake Houston, TX 77058 Yang.Andrew.T@acm.org

Ralph F. Grove Department of Computer Science James Madison University Harrisonburg, VA 22807 Ralph.Grove@acm.org

Abstract

With the growing use of Web technologies in various critical applications, it is important for a Computer Science student, whether undergraduate or graduate, to gain experience in developing multi-tier Web-based applications. These applications provide access to data and services from a remote server, which may in turn access databases distributed across the enterprise network or the Internet. The fact that the Web is becoming the next-generation computing platform makes the introduction of Web-based application development into the Computer Science curriculum an important task. In the new Computing Curricula 2001 report, Net-Centric Computing is one of the components in the Computer Science Body of Knowledge , as recommended by the joint ACM/IEEE Task Force on Computing Curricula. (The Computer Science Body of Knowledge is attached as Appendix A of this paper.)

The Computer Science Body of Knowledge is composed of 14 modules. Core hours are recommended for all but two of the modules. The total number of recommended core hours is 277. The modules, as well as their respective recommended core hours, are listed in Table 1. The respective percentages of recommended core hours, when compared against the total recommended core hours, are also included in the table. The Net-Centric Computing module, for instance, contains 15 core hours, which is 5% of the total recommended core hours for the Computer Science Body of Knowledge.

Modules	Recommended core hours	Percentage of the core
PF. Programming Fundamentals	65	23%
DS. Discrete Structures	37	13%
AR. Architecture	33	12%
AL. Algorithms and Complexity	31	11%
SE. Software Engineering	30	11%
OS. Operating Systems	22	8%
SP. Social and Professional Issues	16	6%
NC. Net-Centric Computing	15	5%
IM. Information Management	10	4%
IS. Intelligent Systems	10	4%
PL. Programming Languages	5	2%
HC. Human-Computer Interaction	3	1%
CN. Computational Science	0	0%
GR. Graphics	0	0%
Total recommended core hours	277	100%

Previous experience	Number of students in each category	Final grades
Both VB and Java	1	A
Java but no VB	5	AABCC
VB but no Java	2	BC
Neither Java nor VB	4	BCWW

A Web-Based Development course might be implemented in any of a variety of formats depending on the degree of significance attached to the topic and the mission of the program in which it is taught. The course could be packaged for a single semester or as a series of two courses, or for an equivalent number of quarters. It might also incorporate an emphasis on software engineering, e-commerce, networking, artificial intelligence, or another related topic. More or less emphasis might be placed upon certain aspects of building web-based applications, such as GUI development, communication protocols, and database design. The course described here is a one-semester course, of three credit hours, that focuses on providing students an understanding of and experience with multi-tier web-based applications.

Relatively more emphasis is placed within the course upon the middle layer of the multi-tier architecture, the business logic service, since this part of the multi-tier application has less coverage in the traditional curriculum than either front-end design or database services. The focus is on server-side programming of application logic, with enough of the outer layers included as is necessary to complete students’ understanding of the issues, technology, and design patterns prevalent in web-based applications. The course is thus complementary to existing curriculum that covers interfaces and database design.

One important question that arises in teaching the course is what set of technologies to use. Server-side component design can be based in Java, with servlets, JSP, JDBC, and related API’s, or it might be based in CGI scripts, or it might comprise ASP and related API’s. Rather than provoke a language-war, our approach is to include an overview of available technologies to students and to then select the technology set that is most practical, based upon the instructor’s experience, students’ background, and the available tools and platforms for development. Thus, students might develop Java servlets one semester, and use ASP the next. The central design themes and architectural patterns remain constant, however. As we learned from the first offering of COSC415 (see section 3), a "favorable" alternative is to teach Web-based development in the first semester, using multiple languages, while teaching components-based development in the next semester, also using multiple languages.

We believe that course design should always begin with a clear statement of student-centered learning objectives. Our objectives are stated in demonstrable terms, to give students a clearer idea of what is expected of them, and to use as a basis for creating exams.

Upon completion of the course, students should be able to:

• Explain the use and general format of principal Internet communication protocols

• Describe the purpose, strengths, and weaknesses of client-side program components, including browsers, scripts, and applets

• Describe the purpose, strengths, and weaknesses of server-side program components, including CGI scripts, ASP, JSP, PHP, and servlets

• Explain the structure of three-tier and N-tier web-based applications and describe the required software components

• Develop small web-based applications including an HTML interface, a database interface, and a server application to provide complete system functionality

• Effectively employ security protocols in developing web-based applications

• Use appropriate methodology for design, development, and testing of web-based applications

The first four objectives are of a general nature, related to principles of developing web-based applications. The last three are more functional, relating to actual development of web-based applications, which is the culmination of the course curriculum.

Prerequisite knowledge and ability is kept to a minimum, in order to make the course open to as wide an audience as possible. Since a significant part of the course is practical, involving application development, programming skills and application development experience is a must. The application development experience need not be extensive, however. A second course in programming (even if the first was at the high school level) is generally adequate. It would be best, of course, for students to have had experience using the particular programming language that is being used in the course (Java, Perl, etc.). At least a closely related language is necessary. It is easy for C++ programmers to learn to write Java code, but much more difficult for Visual Basic programmers to do so, for example.

The course is divided, chronologically, into four sections. The first two sections provide an introduction and overview of the technology and design issues involved in building web applications. The third section supports the development of a web-based application. The final section includes a slightly expanded view of the web-based application context.

The goal of section one is to give students a general introduction to relevant protocols, languages, and technologies. It is, in a sense, an introduction to the “language” of web development. At the same time, this section is intended to help students develop a conceptual framework for understanding the global design issues that are to follow.

Section I: Fundamentals

a. Networking Fundamentals: sockets, IP, TCP, HTTP

b. Client-side Components: HTML, XML, browsers, applets, HTML forms, JavaScript, VBScript.

c. Server-side Components: Web servers, servlets, CGI, JSP, ASP, PHP, application servers.

d. Data-base Components: SQL, JDBC, database servers

Section two develops a more holistic view of web-based applications by focusing on issues of design and architecture. Typical web-based application architectures are reviewed, from simple client-server interaction to complex multi-tier applications with distributed services. Different varieties of services are examined, including transaction, database, and directory and legacy servers. Security issues such as identification, confidentiality, privacy, and related technologies are included here as well, since they should be an integral part of any application design.

Section II: Architecture and Design

a. 1..N-tier designs

b. User interface versus business logic

c. Back end servers: database servers, directory servers, transaction servers, interfacing to legacy systems

d. Security issues

e. Object-oriented modeling for Web applications using UML & WAE

The third part of the course presents the technologies and programming techniques necessary to build the middle layer of a complete multi-tier application. This particular topic list includes Java-related and ASP-based technologies, but it could easily be replaced by any two functionally equivalent set of tools, at the instructor’s discretion. Our feeling is that once students understand the functionality of the middle layer of software, that knowledge can easily be transferred to any appropriate technology set.

As discussed in section 2 (Current Practice), a common "problem" of teaching Web-based development is that very often the course focuses too much on a single technology. By using at least two comparative server-side technologies, the course provides the students a broader picture of Web-based development. A "comparative" approach will also strengthen the students' understanding of the underlying concepts and Web-based architecture.

Section III: Development of multi-tier applications

Java-related

a. Setting up the Java servlet engine

b. Fundamental Java servlets: servlet life cycle, Request and Response

c. Session Management and cookies

d. Dynamic HTML generation

e. Data Management using Java Database Connectivity (JDBC)

f. Java Server Pages

g. Integrating Java servlets and JSP

ASP-based

a. ASP Object Model

b. Fundamentals of ASP: getting started

c. Basic ASP: input, output, variables, arithmetic operations, strings, arrays

d. Control structures

e. Object-Orientation in ASP: objects, properties, methods and events

f. Session Management: Applications, Sessions, Cookies

g. Database Access with ASP: ADO object model

The final section of the course is intended to give students a look at the next level of complexity in building web-based applications. Topics include component frameworks for heterogeneous distributed applications, directory access, and search engine interfacing. In addition to providing a look over the horizon for students, this section provides material for discussion in class while students complete the development of a web-based application using information learned in the previous section.

Section IV: Special Topics

a. Distributed component frameworks (COM/DCOM, CORBA, RMI, Jini)

b. Secure directory access using LDAP

c. Search engines

The course design depends on three critical pedagogical components: a running case study, a significant project assignment, and teamwork.

The role of the case study is to provide an ongoing basis for examples that illustrate technologies presented in class. Having a consistent case study throughout the class provides students a familiar context in which new techniques can be explained, and it helps to illustrate how various techniques are integrated. An HTML form might be developed to illustrate the construction of a user interface, for example, and then that same form would be used to explain server-side processing of the data it contains. The case study also serves as an example for project development work done by the students. A web chat facility requiring user registration and login is a possible case study ­ it requires a user interface, server-side processing, and persistent data, which are the essential elements of the applications being studied.

Completing a significant project that is a web-based information system of some sort will give students the chance to integrate what they have learned and to synthesize a solution to a new problem. We know that students also derive satisfaction from building their own useful working application, especially one that has a visual (user interface) component. The scope of the project is critical, however. It must address the learning objectives of the course by incorporating the principle material covered, it must be different enough from the case study that was presented so that it requires creative thinking, but it must be manageable within the available time that students can be expected to contribute to the class. A records management application (directory, inventory, etc.) or a textual web browser (with memory) would be appropriate, for example. If possible, students should be given the opportunity to present their finished products to the class, so that they can learn from each other and so that they get the satisfaction of showing their finished work to the public.

Having students work in teams as they complete their project has several benefits. First, it makes development of a moderate-sized web-based application more practical, since the work can be shared among two or three students. This is especially important if the project product is to include design or narrative elements. Working in teams also gives students an excellent opportunity to learn from each other. Their shared experiences can be more enlightening than time spent in the classroom. One additional benefit is that assigning projects to teams means that fewer individual projects are completed, and this makes it practical for students to present their finished product in the classroom (eight presentations instead of 24, for example).

In order to try out the techniques presented in class and to complete their assigned project, students will need access to the complete set of tools and servers that support web-based applications.

One or more web browsers must be available to test user interfaces and system functionality. This is not a big problem, since most available computers have one or more browsers available. We recommend that students test all code that they develop using both Netscape and Internet Explorer at least. For thorough testing, students can also test using multiple versions of these, and with other less widely used browsers (e.g. Opera, Mozilla, and Konquerer).

Though the use of integrated development environments sometimes generates controversy, we advise students to use such tools for development of HTML as well as server-side code. Once students understand the essential syntax of a language and can effectively write code, there is little to be gained from denying them the use of integrated tools. There are a variety of freeware and commercial tools available, so finding an appropriate tool set is usually not a problem.

As they develop a project, students will need certain normally restricted forms of access to servers, which can be a problem. To test CGI scripts, servlets, and active server pages, students will need permission to place their code in the appropriate server directories. Even more important, however, students will be writing code that runs at a privileged level in the operating system, which raises the possibility of accidental (possibly malicious as well) damage and improper access to system resources. The simple solution to the problem is to provide a server for the exclusive use of students in the class, so that damage will be contained and can be easily repaired. Depending on the robustness of the particular server tools being used, however, it might be necessary to frequently restart or even rebuild the server. A team of students from the class can be given responsibility for this as well, giving them additional good experience in managing web-based applications.

To complete a comprehensive project, students will need access to a database server as well. In this case, however, they need only enough information to read and write the database, which can be initialized beforehand. The same set of data can be used to populate an initial database for each project team, and procedures for re-initialization of the data can be created so that students can start with a clean data set when testing their projects.

The course described above is a one-semester comprehensive course in web-based information system development. A more extensive treatment of the topic, in two semesters, might expand the core topics in any of several different directions. One possibility would be to include more about user interface development, including both graphical design and the use of client-side scripts such as JavaScript or VBScript. Another possibility would be to include more coverage of database development and database tools. A second semester would also allow students time to look at a more diverse set of development technologies, including CGI, ASP, JSP, PHP, etc. There are several related topics that would complement the core topics as well, including cross-platform connectivity (CORBA, DCOM, RMI, Jini), and various domain-specific API’s.

There is a clear need for treatment of web-based development in the CS curriculum. The growing significance of the World-Wide Web as a medium for business, education, commerce, government, and virtually all human communications implies that all information technology specialists will need to be familiar with web-based applications. This fact is reflected in the inclusion of net-centric computing in Computing Curriculum 2001.

Teaching a web-based development course presents several issues to curriculum designers. One issue is choosing a set of technologies to present to students from among the many that are available. Another is deciding what relative emphasis to place upon networking protocols, server-side operation, client-side operation, and database services, which are the primary components of the multi-tier application architecture. Related issues such as information security and software engineering must be considered as well. Finally, there are practical issues, such as how to provide a flexible but secure development environment for students, and how to keep abreast of changing technology.

The course design presented here reflects the requirements of Computing Curriculum 2001 as well as the authors' practical experience in teaching a web-based development course. This design is not offered as a one-size-fits-all solution, but rather as a practical guide to developing a course that is appropriate for the environment for which it is taught.

7. Appendix B: Sample Listing of Computer Science Areas [7]

8. References