December, 2000 | If you want to learn woodworking,
you can enroll in an evening course like "Furniture Making
101," then go to your favorite hardware store and buy some
tools (the fun part). The good news with XML is that its
tools and even training are often free and always a lot
less expensive than what you are accustomed to paying for
other categories of software. Another nice benefit of XML
is that you can often do much more with your tools than
you would first guess, and their power is growing fast.
XML was originally designed as a way to develop more functional
sets of tags for Web sites, also called Document Type Definitions
(DTDs), models, schemas, markup languages (MLs), or vocabularies.
XML is more than that, however. The World Wide Web consortium
("W3C") is close to releasing its final version of the XML
standard for graphics ("Standard Vector Language"). RealNetworks
seized upon XML (via the Synchronous Multimedia Integration
Language) for developing Web-delivered multimedia via its
Real player (think of the Real Player as a browser for SMIL
As readers of this column by now understand, XML comes
in two fundamental flavors: well-formed and valid. Suffice
it to say that the major difference between the two is that
well-formed XML files do not use an explicit DTD (although
they use one implicitly), while valid XML files require
an explicit DTD. All valid XML files are also well-formed.
Before you can get started with valid XML, you must have
a DTD. That means you either must create one yourself or
use one of the hundreds of established and emerging ones.
Luckily, there are hundreds of free DTDs (typically housed
by the "W3C," or by industry groups wanting standard ways
to communicate. Typical places to look for the free DTDs
are the W3C (www.w3c.org)
for HTML, XHTML, SMIL, or the Scaleable Vector Graphics
(SVG); Microsoft (www.biztalk.org)
for industry initiative DTDs and Schemasthe next generation
of DTDs; and Oasis' www.oasis-open.org,
(or its clearinghouse www.xml.org),
likewise a source of emerging industry-standard models.
Although you can view any DTD or schema with a word processor,
doing that is akin to looking at Web sites by examining
their HTML codepossible, maybe useful, but not for
the uninitiated. Luckily, there are low-cost tools that
let you view these graphically, modify them, convert from
one format to another, or start from scratch. Extensibility
(recently purchased by TIBCO) offers a Java-based interactive
development suite called "TurboXML" (www.extensibility.com).
Now at version 2 and available for Windows, Mac, or UNIX,
it costs under $300 (less if you buy part of the toolkit).
A similar suite at around $150, tuned for Windows performance,
is XML Spy (www.xmlspy.com).
We consider this kind of suite a required part of your XML
toolkit. Both suites provide graphic development or conversion
of document models, let you create XML documents, and provide
loads of other features. Both suites can even create XML
models from your Microsoft Access databases, or even from
well-formed XML documents.
One strategy we like for moving up to XML works well if
your content is already HTML. The W3C provided a stepping
stone called XHTML, the Extensible Hypertext Markup Language.
Converting to XHTML gives you disciplined Web code that
is viewable with modern browsers, but since the result is
XML, you can then add or modify your document model (see
the previously mentioned tools) and customize as you wish.
One excellent conversion tool is HTML Tidy, available free
from the W3C. This tool is also bundled and integrated with
Allaire's Homesite, which itself is bundled with the most
popular Web development tool: DreamWeaver.
One of the finest XML authoring tools we've seen is also
bargain priced, compared with less functional tools of a
couple years ago: SoftQuad's XMetaL (www.softquad.com),
now at version 2, and available from SoftQuad for under
$500. We continue to put XMetaL through its paces with new
DTDs, and remain amazed how easily we can turn around valid
XML documents for prototypes or production systems. Although
you can also author with Spy and TurboXML, XMetaL provides
a WYSIWYG and customizable environment suitable for mainstream
users, while also providing a more code-oriented optional
Interested in Web streaming multimedia, perhaps sound,
slide shows, or even video? RealNetworks offers several
products to produce streaming SMIL-based products. One of
these, RealSlideshow, let's you drag-and-drop audio clips
and graphics to build surprisingly high-quality streaming
shows. Buy the "Plus" edition and you get free hosting for
As for freebies, Internet Explorer (version 5.5 as of
this writing) has an excellent internal XML parser and is
building on Microsoft's XML commitment. Netscape 6 promises
more, and is aiming at an end-of-year release. RealPlayer
from RealNetworks provides Web-delivered audio and video,
based on the W3C's SMIL standard.
It may not last, but there are still lots of free, time-limited,
and other resources available. Three of our favorite Web
stops for these are www.xml.com/pub/resourceguide
(managed by Seybold and O'Reilly), www.software.ibm.com/xml,
These sites often offer software for free or for evaluation.
Try asking hardware store sales reps if they will let you
try before you buy!