40.4 Improving the Product Design

There are certain common points that need to be considered when designing the interface and functionality of a hypermedia product. Although the points listed here have been identified based on our work on the DAGS multimedia proceedings, they are valid for any hypermedia publishing effort.

Improved linking

Currently, digital web talks are not yet fully linked to HTML papers. Since there is usually some correspondence between a submitted paper and the talk held at the conference, linking fragments of the talks to different sections of a paper is an obvious extension. Eventually, it would also be meaningful to reference multiple HTML documents from within a talk. Users could read relevant sections of a paper and listen to the speaker simultaneously. The AWCF application could easily be extended to automate linking individual slides to specific sections of various papers. If each slide were to be linked via an individual URL, papers could also be submitted as a collection of hypertext files instead of one long piece of text. Providing such links between the paper and the talks would either involve human experts to do the indexing and linking or the use of automatic indexing methods as described in part I.

Support for multimedia synchronization

An interface like that of the DAGS'92 talks requires synchronization to, e.g., support the transition from one slide to the other at key points in the audio. Unfortunately, HTML was not designed with sufficient support for such multimedia synchronization, and it is not likely that HTML will support it in the near future. At present, the best solution seems to be to enforce synchronization by segmenting the audio and explicitly requiring users to reload the next audio clip upon encountering the next slide, as we did for the DAGS'95 talks. Java and JavaScript now offer an alternate solution by allowing tighter control on the loading of new frames.

Audio over the Internet

http://www.realaudio.com

The biggest disadvantage of the "AU" audio file format chosen for DAGS'95 is the long download times that modem users experience. Audio on demand for Internet delivery is a recognized need and market opportunity. For instance, encoder, player and server software using RealAudio technology by Progressive Networks enables users to access RealAudio sound files and play them back instantaneously [Rea95]. Using a RealAudio player helper application or plug-in allows to download a continuos audio stream over a 14400 kb modem. RealAudio bypasses the HTTP practical and directly relies on the underlying UDP protocol. Among other improvements Progressive Networks developed a new protocol for time-based media that supports bi-directional communication between clients and servers allowing RealAudio users to pause, fast forward, and skip to particular sections. Progressive Networks also came up with a loss-correction system that minimizes the impact of lost packets over the less reliable UDP protocol and even degrades gracefully when there is packet loss.

RealAudio players are currently available for most of the popular target platforms for free, however RealAudio servers come at substantial cost[32]. Nevertheless, the advent of RealAudio and other "sound over the Internet" products will certainly have far-reaching implications on the interface design and audio file format for future digital talks and other Internet publishing products.

Extending browsers

There are many different software tools available for CD-ROM-based multimedia editing. Authoring tools on the web are far more limited. Tools for CD-ROM software development like HyperCard, Macromedia Director, ToolBook, SuperCard, Apple Media Tool, etc., allow to easily implement custom features such as annotation, search, navigation, and layout. Using WWW as a delivery platform means that some features that might have to be programmed explicitly when creating an application for delivery on CD-ROM, are hardwired into the WWW browser. Predefined features that add to the quality of the talks interface include the ability of browsers to keep track of locations visited and the ability to add bookmarks. A significant pitfall of WWW browsers is missing support for user annotations (see below). Generally, functionality that goes beyond those provided by the browser can be provided through CGI or Java/JavaScript programming. Java applets that provide additional navigation functionality extending web browsers are described in part I.

Support for annotations

Given the preeminence of annotations and linking in the hypertext community, it is somewhat surprising that neither HTML nor current WWW browsers provide real support for shared annotations or user-links being added to existing documents. This lack makes HTML inconvenient at best for true hypertext publishing. Fortunately, researchers are developing extended browsers and support systems for shared annotations [Roe95].

Usability testing

The ultimate question, of course concerns the effectiveness of the final result. We believe that the multimedia proceedings provide most of the content of live talks and linear papers, with the advantage of random talk access and hypertext linking. Although there are many situations where the printed book still surpasses any hypermedia document, there are obvious advantages to hypermedia publishing, as has been demonstrated by the exponential growth of the web and the ever growing number of CD-ROMs titles available.