Hypertext standards

Draft

A short article on hypertext standards and systems.

See also Hypertext

Standards

Resources

See URN

HTML

HTML has more links than just the "a" tag

needs some elaboration

• The "rel" and "title" attributes
• The "base" element
• The "link" element
• The "meta" element

The basic link mechanism in HTML is very simple, too simple to build certain kinds of educational applications. To build more sophisticated links in HTML web pages, one has to rely on Javascript. Since the DOM interface (computer representation of page content) is now almost standardized (cross-browser compatible), one can increasingly find pages on the Internet that implement some of the complex link types we described above.

RDF

RDF is a language for representing links between concepts. It's the basis for the so-called semantic web.

XLink, XInclude and XPath

• XLink (XML Linking Language) a W3C specification for creating hyperlinks in XML documents. This standard is badly implemented in web browser. But subsets are used in vector graphics standards. Even XHTML 2 does not use XLink, but adds at least some extensions to XHTML 1.
• Related standards are XInclude and XPath. XInclude is a processor that allows inclusion of several text fragments into a single document. XPath allows to identify these fragments. There exist several implementations for XInclude and XPath. XPath is also an important component of XSLT, a widely used and implemented (IE explorer, Firefox, Opera) transformation language.

Links in vector graphics standards

• SMIL, SVG and X3D make use of a subset of XLink

Topic Maps

• Are a standard to semantically organize resources, i.e. a special sort of semantic network technology. see Topic map
• Topic map systems are deployed either through HTML rendering or special clients.

Links for books

A book is from a cognitive ergonomics point of view also a hypertext. Good word processors can render a text in HTML or PDF with links and therefore turn a book text into a physical hypertext:

A hypertext link always establishes a connection between to related nodes

• Structural links (e.g. all the chapters/sections of a book)
• References (cited documents)
• Footnotes
• Associative links (internal cross-references or references to other on-line texts)

Hypermedia systems

Typically, a hypermedia system should include for the user point of view

• A database of information
• Navigation that includes hyperlinks, buy may also include search
• Multiple media for the presentation of information.

Technically speaking:

• The database can be just any storage technology. I.e. several files, a single file, databases.
• Links are implemented with various technology, e.g. markup languages (like in SMIL) or through programming with event-handlers.
• Whether hypertext is defined with some explicit markup technology or through some binary computer code, we need an interpreter (player) to render the contents.

Navigation and orientation

“the greatest issue of concern in hypermedia programs is navigation. Hypermedia disorientation, popularly known as "getting lost in hyperspace", is the most active area of research on learning from hypermedia. The double-edged sword of hypermedia is that larger databases is that larger databases are more useful, but they exacerbate the problem of getting lost. There are two different issues here: orientation (knowing where you are and where the information you want is) and navigation (getting where you want to go).” (Alessi & Trollop, 2001: 155).

One way to overcome the LostInHyperspace effect is to use userdefinable <-> BiLinks, which we apply on the footer of this page to demonstrate how convenient this is: