9.2 Presentation of Information 191
websites consist mainly of a collection of files written in the Hypertext
Markup Language (HTML) format. There exist many tools for creating these
files. However, constructing the files directly using such a tool is not a very
good way to construct a website. It has a number of serious disadvantages:
- Most of the effort is directed at the visual appearance (presentation) rather
than the actual information (content) on each webpage. - The same information can appear on several pages, so updating informa-
tion requires one to find the information and update it in all its locations. - Small changes in the content can result in a large number of changes to
the website. For example, adding a new person to a department requires
that a series of pages be constructed for that person along with references
to those pages in numerous other pages. Similarly, when a person leaves,
one must delete many pages and remove references on other pages to
the deleted pages. The effect is reminiscent of the “butterfly effect” from
chaos theory, but on a smaller scale. - It is very difficult to maintain a uniform style throughout the website.
Small changes to the style require that a large number of webpages be
updated. The effort involved can be substantial.
The most effective way to deal with these problems is to divide the overall
process of constructing a website into a series of transformation steps. This is
called “separating concerns.” A typical example of how this is done is shown
in figure 9.4. The concerns in this example are:
- Source content. For a biology laboratory this would include the current
projects, the people working in the laboratory, published papers, data and
software, scheduled events, and so on. - Logical structure.The source content is subdivided into overlapping views.
For a laboratory, each project has its own view that includes just those
people working on the project and the papers, data, and software for that
project. There are many ways in which these views overlap. - Presentation. The logical views of the previous step must be converted
into a format such as HTML, a spreadsheet format, or PDF so that it can
be presented to the person or program that is requesting it.
The process begins with source information that could be stored in files or
databases in a large variety of formats. The data are extracted and converted