A Tool For Authoring OHP Presentations Using HTML


Phil Scott

La Trobe University
E-mail: P.Scott@latrobe.edu.au
URL: http://ironbark.bendigo.latrobe.edu.au/staff/pscott/Phil.Scott.html or http://ironbark.bendigo.latrobe.edu.au/staff/pscott/ohpmlps/ohpmlps.html

The World Wide Web provides an ideal model for distribution of teaching material to students in an academic environment. At Bendigo, staff in the Department of Information Technology use the Web to make available lecture notes, tutorial worksheets, sample programs and pointers to useful resources elsewhere. This practice is now common in most universities.

A problem arises when "presentation graphics" software such as Microsoft PowerPoint is used to prepare lectures which are subsequently published on the Web. The alternatives are:

  1. Convert the proprietory presentation graphics file to HTML, the language of the Web. This tends to produce results of varying, but generally poor, quality. It also be be very time consuming, particularly managing conversion of graphic images.
  2. Make the material available on the Web in the original presentation graphics file, and force users to install an appropriate external viewer. Whilst easy for the lecturer, this approach is simply using the Web as a "file distribution" mechanism, and ignores many powerful features that it could otherwise offer, such as cross references using hyperlinks.
Some time ago, we realised that perhaps there was a better way - we could author our lecture notes in HTML, and create a tool which would render them in an appropriate manner for use in OHP-based presentations. Using HTML to author presentations is, in fact, becoming quite a common practice. Where "screen projection" PC-based facilities are available, the presenter can use a normal web browser such as Netscape. We have used this method in the lecture rooms at Bendigo which have suitable display hardware. However we have very few such rooms.

Using HTML as the source format has the additional advantage that the new "Web Authoring" software packages can be used, instead of proprietary presentation graphics packages. It also eliminates the pain of having two versions of the document: one for the actual lecture and a derived version for publication on the Web. One particular advantage of this is that the original document can contain hyperlinks, which can be ignored when the material is being used as part of a presentation.

The use of a web browser as a presentation graphics tool has some disadvantages. The HTML must be authored in such a way that scrolling is not used - our students report that this is very distracting. Best practice seems to be to configure the browser to use a specified (large) font size, with appropriately sized graphic images, and to make each "slide" of the presentation a separate HTML page. In reality, this is simply cajoling the browser into reluctantly accepting a role it was not designed for.

However, as mentioned earlier the problem at Bendigo, as in most universities is that lecture rooms with PC (or Mac) screen projection hardware are very scarce. The need then arises for a system whereby presentations written in HTML can be displayed where the only technology available is an Overhead projector (OHP). What is required is a software utility which can format and print HTML documents in an appropriate style for use on an OHP.

This paper describes the first prototype of such a tool, "ohpmlps". It takes as input an HTML file, written in a defined subset, which we call "OHPML". An OHPML document is perfectly legal HTML, and displays correctly on any Web browser. OHPML simply defines which markups are appropriate to an OHP presentation, and adds some extra interpretation rules. For example, in ordinary HTML the <hr> markup generates a horizontal line. In OHPML, it is used to signal the end of a "slide", and therefore generates a new page of output.

The prototype ohpmlps compiler was written using a standard C/yacc/lex approach, and generates PostScript output. It currently implements most of the markups defined in OHPML, and has proven already to be a very useful tool. There are man potential directions for future development of ohpmlps which we detail in the paper. The transparencies (or slides, as appropriate) used in presentation of this paper will be authored using OHPML and ohpmlps. The prototype ohpmlps software (source code) is available for downloading from the Web page http://ironbark.bendigo.latrobe.edu.au/staff/pscott/ohpmlps/ohpmlps.html

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