Last month we looked hypertext markup language (HTML) and the way it uses tags to define how text or images are formatted. This system is useful because it is widely accepted, but it is limited because it defines only the way things appear on a web page.
One characteristic that wasn't discussed is that tags are invisible to the reader. A web page may be loaded with tags but you don't see them. Every change in font or color, every image, and every link needs at least one tag - but none of them are seen by the reader.
Using hypertext markup language (HTML), anyone can read a web page and see what it says. But, since HTML "knows" nothing about what it describes, it is of little value to a computer.
Imagine that a metal panel manufacturer receives a web document requesting an order for a red roof panel. A person reading that document would see that the panel is supposed to be red, but that information would have to be entered into a separate program before it could be used for accounting, computer-aided production control, or any other automated system.
Imagine another type of tag, again invisible, that could be read by a web browser. If used in the document used to order the metal panel, the metal panel company's computer could be getting information at the same time it was being read. The result might look like this:
The reader would see the word "red" and, at the same time, the computer would extract the color - and other information related to the order - and pass it on to other programs for use in ordering material, start production, or whatever.
This type of tag is now being developed. As an extension of the existing HTML, the new standard is called extensible markup language, or XML. It is already in use for special applications, such as CML (chemical markup language) for molecular information, and MathML for mathematical formulae.
Another standard - aecXML - is being developed specifically for the construction industry. Visit these web sites to see what's happening: www.aecxml.org/, www.microsoft.com/Windows/ie/xml.htm, www.xml.com, and www.xmlx.com.
© 2000 Sheldon Wolfe, RA, CSI, CCS, CCCA