The Historical Event Mark-up and Linking Project

1. History on the World Wide Web

The web now forms one of the world's largest repository of information about the past. Historical web sites range in size and ambition from vast scholarly endeavors, such Athenians, a record of all known people who lived in ancient Athens, to small-scale personal efforts, like Genjirou Inui's My Guadalcanal. Such texts share one important similarity: as works of history, nearly all make assertions about events that took place in the past or argue about those events.

Despite this underlying similarity, each site publishes its information about historical events in a different way. For example, Le Musée virtuel de la Nouvelle-France provides a time-line with links, entitled Explorations européennes en Amérique; in contrast, the Prosopography of the Byzantine Empire comprises articles on individuals, with significant dates included in parentheses. Indeed, markup tools suited to the historian are simply not available. Although the Text Encoding Initiative does provide the means of encoding date and location elements, these are not easily combined into a element representing historical events, nor are there common tools available to manipulate the TEI date elements in a manner suited to historical markup.

The Historical Event Markup and Linking Project (http://www.heml.org) fills this need for a common historical markup language. It defines a common XML schema through which historical documents can be published on the web and provides useful transformations of data encoded according to that schema. The following example illustrates the potential of such a system.

2. An Example

Consider twelve diaries or memoirs, each a different view of the Siege of Sarajevo in 1994 and published on the web. They would include entries about events such as the stationing of troops or the evacuation of a certain region on such-and-such a day. If a standard form of mark-up were used to tag the text that recorded these events and their date and location, a computer could collect this information and associate it with the document. It would then be possible to search for descriptions of events on a certain day, or in a certain region or both, and retrieve references to the proper section of the pertinent memoir or memoirs.

Other alternative views of the events could be produced from these marked-up documents. It is common, for instance, for historical texts to include a chronological chart of events to aid the reader. From our twelve memoirs, each marked up in the same manner, we could create an exhaustive chronological chart detailing every event the texts' editors thought worthy of inclusion. Furthermore, the entries in our chronological chart would refer to their sources, either in printed citations or with a web link. Alternatively, if the mark-up scheme included information about the events' location, the documents could be used to produce historical maps or to search for events that took place in only a certain quarter of the city.

Consider now the usefulness of such a mark-up scheme if it were applied to even a fraction of the thousands of historical documents and web sites published on the web. It would be possible for a curious student to ask what happened worldwide between the years 1500 and 1200 BCE and to receive a list of events linked to scholarly sources or historical arguments. Time-lines and maps could be generated from disparate sources worldwide. Such a scheme would afford us a new and exciting means of communicating about our past.

3. Project Principles

HEML is built with the following principles in mind:

It is as fully internationalized as possible. Thus it encodes and translates between dates in disparate calendrical systems, including the Gregorian, Buddist, Islamic, Hebrew and Japanese. It also fully supports xml:lang tags and related parameters for linguistic localization.
It operates on as large a variety of computing platforms as possible. Because our software is written in XSLT and Java, it will function as part of a server operating on a wide variety of systems, including the Macintosh, Windows NT and free Unix platforms like Linux.
It is free of cost and open-sourced. This project has adopted the open-source model of developement; its source code is available to all from a Concurrent Versioning System server. Furthermore, HEML makes use of several other software packages, from IBM and the Apache group, all of which are similarly licensed. (None of this impedes those who would wish to implement this software in a commercial web server.)
It emphasizes results. Our design cycle begins with the simplest possible schema for an historical event, we then widely explore possible transformations for complying documents. By taking this approch we ensure that scholars considering the use of HEML can see the possible outcomes of their efforts and that improvements in the markup schema are informed by the needs and interests that arise from the problems of presentation.
With little additional effort, it is possible for an educated layperson familiar with HTML to mark up XHTML texts with HEML tags.
4. Technical Discussion

The current HEML project prototype includes:

An XML namespace and related schema to be used either with modularized XHTML or any other XML application. Currently, this defines an event as through composite 'date', 'location' and 'label' elements.
Chronological tables generated from XHTML documents. In order to convert between and compare heterogeneous chronological systems, we have written extensions to the Xalan XSLT engine which employ IBM's International Calendars for Java.
Timelines scaled and dynamically generated in Scalable Vector Graphics, allowing the image to contain links to the source materials from which the graphic was generated. (It is still possible to convert the SVG output into more commonly-used formats, such as GIF and PNG, if necessary.) This transformation is performed on the DOM, using Sun's Java 2DGraphics API and their SVG conversion library.
Historical maps of the events, also rendered in SVG and linked to sources.
5. Theoretical Considerations

Among historians and philosophers of history debate continues over what constitutes historical evidence and how it relates to the work of the practicing historian (Carr 1987:10-15; Elton 1969:112-13; Jenkins 1991:26, 48-50). This project does not seek to solve these problems, much less to impose one approach on the scholar who uses it; it hopes instead to provide a new medium for communicating about the past, one in which this debate can be continued. Though the concentration on `events' in this proposal might suggest that it is best suited for political history, we hope that non-traditional approaches to the study of the past will also be well served by this organizational tool, because it puts all encoded events on equal footing. For instance, so-called microhistory, whether temporal or spatial (Ginzburg 1993:14-15), can more easily be pursued in an organizational scheme in which the life of an Athenian slave, recorded in Traill (2000), is on the same footing as any other event.

It is also true, as Zuern (1999) points out, that the typographical representation of historical events is a rhetorical device. We hope that scholars using our tools will allow their audience to choose the format in which they view their information, as a 'pluggable rhetoric', thus opening it up to further interpretation and discovery.

6. Works Cited

Carr, E. H. 1987. What Is History? 2nd. ed. R. W. Davies London: Penguin.

Elton, G. 1969. The Practice of History. London: Fontana.

Ginzburg, C. 1993. ``Microhistory: Two or Three Things That I know about It'' Critical Inquiry 20, 10-35.

Jenkins, K. 1991. Re-Thinking History London: Routledge.

Zuern, J. 1999. Timelines Online: Hypermedia and Information Architecture in the Representation of Intellectual History.