Towards Advanced Hypermedia: The Minimalistic Java Approach
 
Kai Warendorf
School of Applied Science, Nanyang Technological University, Singapore 639798
wdorf@acm.org

 1    A Minimalistic Approach towards design of advanced Hypermedia

Development of a Java hypermedia application differs from WWW hypermedia development. Where most conventional WWW applications focus on the server, in advanced hypermedia development the focus is on the client application. In addition, development with Java is not based on existing components but will usually be implemented from the ground up. With Java, application design is more extensive. The object-oriented nature of Java encourages a fully object-oriented design.

We present the Minimalistic Java Approach (MJA) as a framework that links the advanced Internet hypermedia design process with implementation in Java. MJA does not intend to be a general hypermedia design methodology, since several extensively-used platform-independent methodologies already exist for hypermedia. Instead, MJA is result-driven and specifically aimed towards implementation. It is minimalistic because it does not rely on any specific development tool. All activities in MJA are based on a strong bottom-up and object-oriented approach to software engineering.

1.1    Consequences of Implementation in Java

Three aspects, specific for Java hypermedia, are addressed in MJA. They are the availability of development tools, the hypermedia authoring bottleneck, and integration with existing hypermedia:

  1. Availability of tools and components: A large software library exists with freely available Ďplug-iní extensions, languages and libraries for WWW browser and servers. In contrast, Java components and libraries for support of existing media formats are rare. This implies that only applications, which cannot be accommodated within the limits of conventional hypermedia development are worth the extra effort of custom hypermedia development.
  2. The hypermedia authoring bottleneck: A second issue for hypermedia development is the central role of the authoring process. Without a supportive authoring environment, realization of a real world hypermedia application is laborious. This hypermedia authoring bottleneck [Nanard and Nanard 1995] is a major factor in the success or failure of new hypermedia architectures. Well-designed authoring tools or adaptation to existing hypermedia standards remove the bottleneck.
  3. Integration with existing object-oriented hypermedia design: Among various hypermedia design methodology alternatives, two were selected for MJA because both methodologies share language- and tool independence, as well as full object-orientation. The Extended Object-Relations Model (EORM) [Lange 1994] is based on the definition of a class hierarchy of semantically rich relationships. These linked classes allow designers to express the complex relations between hypermedia objects in fully object-oriented content. The objects are central in EORM because complex semantic information regarding hypermedia object relations can be stored in a single object. EORMís relevance for Java based hypermedia design is to improve the conceptual shortcomings of most existing direct and non-semantic hypermedia link models.
The second hypermedia methodology in MJA is the Object Oriented Hypermedia Development Method (OOHDM) [Rossi et al. 1995]. It is a complete and graphically oriented methodology, specializing in hypermedia user interface definition. OOHDM applies graphical notation to define abstract data views, which express user interface dynamics in petri-nets. The communication between objects is expressed in configuration charts. With its graphical notation, OOHDM complements EORM, in particular for user interface specification.

1.2    The In- and Output of Java Hypermedia Design

MJA follows the waterfall model of software engineering, with seven development phases [Figure 1]. The top two layers display the design-input elements. The top input layer display is specific for Java; the second layer contains general design input. In seven phases, Java classes are defined, and after repeated refinements integrated in one prototype application. In MJA, Java source code has a role as a tool-independent design formalism. The language dependency of MJA promotes the direct implementation of abstract concepts from object-oriented modeling, closely integrated with the Java key technologies. The strong bottom-up approach, combined with prototyping and inclusion of two hypermedia design methodologies aims to overcome the incompleteness of abstract object-oriented software design, which are insufficient when used in isolation [Bryant and Evans 1994].
 

Figure 1: The Minimalistic Java Approach (Italicised items are optional, depending on availability)
 
2    Conclusion

We have introduced Java as a mature platform for advanced Internet hypermedia. With its platform independence, continuously increasing multimedia capabilities, and flexible distributed architecture, a hypermedia browser implemented with Java can eliminate various limitations of WWW hypermedia.

3    References

[Bryant and Evans 1994]. T. Bryant and A. Evans (1994). OO Oversold - Those objects of obscure desire, Information and Software Technology, (36) 1, 35-42.

[Lange 1994]. D. B. Lange (1994). An Object Oriented Design Method for Hypermedia Information Systems, Proceedings of the 27th Annual Hawaii International. Conference on System Sciences, 366-375.

[Nanard and Nanard 1995]. J. Nanard and M. Nanard (1995). Hypertext Design environments and the Hypertext Design Process, Communications of the ACM, (38) 8, 49-56.

[Rossi et al. 1995]. G. Rossi, D. Schwabe, C. Lucena, D. Cowan (1995). An Object Oriented Model for Designing the human- Computer Interface of Hypermedia Applications, Proceedings of the IWHD 95, 123-143.