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Authoring and Design for the WWW



This information aims to give readers a deeper understanding of the strengths and weaknesses of HTML, not instruction in its use. Increasingly, software tools will protect authors and designers of Web documents from needing to originate, edit or even see the HTML codes which are at work within their documents (see Transparent HTML).

HTML, the HyperText Markup Language, is based on SGML, the Standard Generalised Markup Language, agreed as ISO 8879. HTML is actually defined using an SGML Document Type Declaration.

SGML was designed specifically to deliver the advantages of functional description (described below, p29). Not all of the advantages of this approach have actually been carried over in the way HTML is defined, even in recent versions. If its authors had anticipated the enormous influence of HTML arising through the explosion in use of the Web, they would probably have defined it with greater thought for future development. HTML created the success of the Web, but was not designed with that success in mind, most particularly the wide range of media and forms of interaction which it is now expected to support. Nevertheless, it provides a workable document structure which can have other media appended to it.

Unlike the majority of file-formats, such as those for word-processors or multimedia packages, the specification is open, published, and can be interpreted by any browser package, of which Mosaic, Netscape and Internet Explorer are only examples.

The purpose of HTML

HTML aims to overcome four problems which have arisen though lack of standards. These problems have been that: HTML has its own answers to these problems, while Acrobat (see Appendix Three, p104) has others.

Proprietary hardware and software formats

HTML is an evolving (informal) international standard which aims to bypass the barriers of proprietary systems.

Fonts are property

HTML does not transmit fonts from the publisher to the user. The fonts used are those on the user's computer. Plans are afoot to address this problem directly, rather than side-stepping it as now (see The future p54)

Users constrained by hardware

HTML allows the content to be displayed in different ways on differing hardware. HTML instructions which cannot be interpreted at all by the user's computer are ignored, rather than producing an error.

Documents self-contained, unconnected

HTML offers a basic but effective system for linking any part of a document to any part of another document, regardless of where it is sited. HTML allows document authors to specify:

HTML achieves these objectives using text files containing only ASCII characters (the basic but widely adopted standard for specifying the alphabet, numeric digits, and some simple punctuation). ASCII character codes are recognised by almost all the world's computers, and as such offer a means of communication between one computer and another. Unicode, the replacement for ASCII, will provide better support for extended character sets, but the principle remains the same. Other, non-text, media delivered in the context of Web pages each have their own cross-platform formats, but not all of these are open, public formats like HTML.

Important characteristics of HTML

Layout as well as content of text files

Word processors, presentation packages and multimedia authoring packages can all specify the layout of text and other media components, but do so in a way which is proprietary and often uses codes which are beyond the standard ASCII set. HTML is by it nature standardised across all platforms (though there will always be difficulties due to new versions of standards emerging which the available browser software then does not match). HTML takes a relaxed attitude to where things appear on the user's screen. This results from 1 not specifying the fonts, with all their concomitant information about line-length, line-spacing etc and 2 not wanting to make assumptions about the dimensions and other characteristics of the user's screen.

Links between component parts of a hypertext system

There are a number of other hypertext software systems such as Guide, NoteCards, HyperCard etc. They use proprietary, closed means of describing the hypertext linkages and the interactions which are offered to the user. HTML standardises the interlinking of document components. By using URLs, which provide a unique standardised address for every document on every server, HTML is able to treat all HTML documents as equally accessible, regardless of their location.

Links to other media files such as pictures or animations

Most interactive multimedia packages are able, to a greater or lesser extent, to integrate various media components into a single surface. HTML originally side-stepped this problem. Rather than display different media as integrated components of a single document, HTML specified the kind of data to be found in the file, to which the browser package responded by opening a suitable viewer' a small self-contained package which opened up alongside the browser to display this foreign' media type. Increasingly, browsers can display these alternative media within the main browser window, with at least some control over where in the window they appear.
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