Above and Beyond: Understanding Metadata

By Nate Zelnick

SMIL Meets XML

In the demonstration application I showed in the last XML File, I introduced the concept of metadata without explaining what it is or what it is for. I hope the wait wasn't too much, because in this column I'll answer all of your burning questions.

Meta is one of those prefixes that has been so abused that it barely has meaning. Its origin is Greek and it means "above". So while most people say that metadata is data about data, it literally means "above data" just as metaphysical means above the physical.

This may seem like meaningless semantics, but it helps to conceptualize what metadata is about. When you view something from a great height--like from a plane flying at 10,000 feet--general features of the landscape that you couldn't see from the ground are much clearer. On the other hand, little details are lost. Maps provide a high-level guide to terrain that is impossible from the ground. Metadata works the same way--it provides a high-level view of something, defining general structural information about it. It's good for generalities, but is really lousy when you start to get into specifics.

The CDF example we looked at in the last column is a great example of an XML vocabulary that was designed to sit above a set of resources and describe them as a single, integrated channel. If you need a refresher, here's what that file looked like

. In fact, most of the early XML vocabularies are designed to act like CDF--as aggregators of existing resources that create some kind of joined structure with its own internal rules of connection. The newly approved World Wide Web Consortium recommendation SMIL (Synchronized Multimedia Integration Language and, yes, pronounced "smile") is another good example.

SMIL defines how multimedia elements--pictures, video clips, sound files and text--work together. Where CDF organizes resources into a tree of related elements, SMIL's axis of organziation is time: it defines whether elements are presented together (synchronized in parallel) or are launched sequentially. RealNetworks will use SMIL as a primary format, which means you'll be able to write streaming multimedia presentations that will run in any browser using standard HTML tools. Allaire Corp., the company I work for, will integrate SMIL into its HTML editor just about at press time.

[ Click here to move to the next part of the article
(with the code and stuff :-) ]

Refresh Daily
Join Editor-in-Chief David Fiedler The Editor With No Time and find truth, justice, and a clue or two.

[ Site Map ]

ActiveX / VBscript

Animated GIF Archive

Browsers

CGI / Perl

Database Connectivity

E-Commerce

HTML-Advanced: DHTML, CSS

HTML / Site Authoring Tools

Intranet/Groupware

Java

JavaScript

Multimedia: Audio / Video / Streaming Technologies

Opinions

Refresh Daily: Editorial Column

Security

Servers & Server Tools

Site Design / Graphics

Site Management / Marketing / Log File Analysis

VRML / 3D

XML