Document Design

This site targets an audience that represents a broad spectrum of the global Internet community. The audience includes the educational community, tsunami and interdisciplinary researchers, hazard management professionals, and people living in tsunami-threatened coastal communities. The WWW's interface design and document content were strongly influenced by the technical constraints imposed by the wide range of network connections and browser applications utilized by the target audience.

Internet Connections

Many types of Internet connections exist. The fastest connections, commonly available on university campuses and at large corporate facilities, are Ethernet connections. Users accessing the Internet over Ethernet connections can consistently realize file transfer rates, or throughput, of over 100 kilobytes per second (KB/s). Many of this site's potential users are limited to dial-up Serial Line Internet Protocol (SLIP) or Point-to-Point Protocol (PPP) connections through modems, with typical baud rates (bits per second) of 9600 - 28,800, limiting throughput over these dial-up connections to between one and three KB/s .

This wide range in throughput poses a significant development problem as multimedia resources are information-rich and hence inherently large in file size. Image files, even when stored in the compressed formats described later in this document, can be well over 100 KB in size. Animations, even relatively short clips several seconds in length, can be one or more megabytes (MB).

Consider a typical WWW document from this site which may have several small in-line images, usually about 10 KB in size each, and some text. The total amount of data that must be downloaded by the user from the server of such a page might be about 50 KB. The Ethernet-connected user would get this new page in about 0.5 s at 100 KB/s throughput. Comparatively, the dial-up-connected user would have to wait over 50 s with a 9600-baud modem. For the dial-up user to download and explore the 60 MB of animations, audio clips, images, and text currently on the WWW tsunami site, it would take over 15 hours at 9600 baud. Clearly, the dial-up user must be selective in the information that he/she chooses to access. To be selective, however, the user must be presented with clear textual and graphical cues to the information available.

Much effort has been taken to present information on this site in the least data-intensive format for the primary links. Additional link-options, intended for users on high-bandwidth connections, are available to provide access to data-rich resources such as high-resolution images and animations. Documents presenting annotated images contain small, low-resolution in-line images. These in-line images serve as links to higher-resolution images, which may be 100 KB or more, that the user can select when a more detailed image is desired. The number of in-line images per document has been kept to a minimum as well, with typically fewer than 5 in-lines presented within a document. Also, an annotated individual frame from each animation is displayed to provide users with a visual cue as to the content of the animation. With the exception of the high-resolution images and animations, most of this site's documents have been kept to well under 50 KB, allowing even dial-up users to realistically download and browse through documents containing in-line images.

Browser Applications

In addition to the at least two order of magnitude difference in throughput realized by this site's target audience, several different browser programs are currently used. Although most graphics-capable browsers currently support HTML 2.0, many do not yet support the newly-proposed standard, HTML 3.0. The newly-proposed standard implements several features, including table formatting and sophisticated image formatting, not available with HTML 2.0. Several browsers, including Netscape's Navigator 1.1N and Mosaic 2.0, do support HTML 3.0 to a limited degree. In particular, Netscape's Navigator 1.1N supports all of the HTML formatting instructions used for this site's documents. Navigator 1.1N is freely available to the academic community, while Mosaic is freely available to any user through the NCSA at the University of Illinois. Given this availability, a decision was made to use many of the proposed HTML 3.0 features. Users with older software will have to upgrade to an HTML 3.0 compatible browser to properly view this site's documents that contain tables and aligned images.