A Vision for Open Hypermedia Systems Nürnberg and Leggett

3.1 Scenario Synopses

Taxonomic (full scenario link). Botanical taxonomists build taxonomies over samples of plants. Taxonomies consist of taxa and specimens. In this case, a specimen is a plant sample and some data about the sample, such as collection date, collection location, accession number, etc. A taxon is an abstraction that groups together like specimens and/or like taxa. It has a name, a set of characteristics, and a group of children specimens and/or taxa. Taxa are singly parented.

Many difficulties exist in managing these botanical taxonomies. Firstly, not all taxonomists agree on the same set of taxa over a given set of specimens. Secondly, even if two taxonomists agree on what taxa should be constructed, they may disagree on the grouping criteria for some subset of the taxon. Thirdly, even if they agree on these two issues, they may disagree on the attributes of some subset of the taxa, such as name. Fourthly, even if two taxonomists agree on all of these issues at some point in time, the taxonomies they create may change over time, as new data are added, new interpretations are made, etc.

In addition to the creation and manipulation of taxonomic structure, the characters also want to be able to add and manipulate navigational hypertext structures over their specimens, taxa, and taxonomies.

The scenario considers various problems encountered by botanical taxonomists as they manipulate their taxonomies on-line.

Spatial (full scenario link). People faced with the task of organizing pieces of information may be able to use spatial hypertext tools to help them perform this task. Spatial hypertext systems take advantage of people's ability to organize information spatially. In these systems, a piece of information (datum) is represented by an object with certain visual characteristics (shape, color, etc.) that help determine the "kind" of information it is. A given datum may have its visual characteristics changed by a user. Additionally, the image of the datum may contain text and/or other information.

Users are expected to place like data into spatial structures such as stacks, vertical lists, etc. These structures may themselves be placed into structures, and so forth. For example, several vertical lists may be placed side by side, forming a group of lists.

The spatial hypertext system should be able to recognize the spatial structures generated by users and allow users to treat all objects in such a structure as a unit for certain operations, such as movement or deletion. It recognizes these structures by conducting a "spatial parse" of the space in which the data reside. An important aspect to the structure generated by a spatial parse is that it is dynamic. Repositioning one or more data may invalidate the results of a previous spatial parse. Furthermore, it is difficult to modify the results of a previous parse to account for data movement. Also, this parse is relatively (time-wise) inexpensive to perform. This means that in this scenario, there is no reason to keep the results of a parse after data are moved. Instead, new structures can be generated by the parser as requested.

The scenario concerns a character who uses a spatial hypertext system to organize his thoughts about a paper he is writing.

External (full scenario link). Irrespective of the final forms of the OHS reference architecture and protocol, users will always want to use tools that are not integrated with OHS services. This may be because the appropriate wrapper has not been built for a particular tool, the tool provides OHS-like services in a way not compliant with OHSWG standards, or the tool acts as an "extra-systemic" client or server to programs that do comply.

In this scenario, Bob uses several tools that are not integrated into any OHSWG system. He uses these tools alongside his OHSWG tools.

Auto-indexer (full scenario link). There are many WWW search engines that work in the following way. Some automatic indexer program visits a WWW page and indexes its content against its URL. It then follows the links from that page to other pages, where it performs the same process. This obviously takes a long time. (Consider that when the AltaVista search engine was being prototyped in December 1995, DEC estimated that the WWW contained over 50 million indexable documents [DEC 1997].) This index cannot be built by hand. Some autonomous program, once started, must traverse the WWW structure automatically.

In this scenario, Homer wants to build just such a search engine. However, he wants to build indexes of documents in the OHSWG space instead of the WWW space.


Peter J. Nürnberg, John J. Leggett
HRL, CSDL, Texas A&M
original page URL: http://jodi.ecs.soton.ac.uk/Articles/v01/i02/Nurnberg/scen_synop.html