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The XML Family
of Technologies
44
What XML functionality do Browsers Support?
XML support has been an increasing priority in recent releases of the mainstream Web
browsers. However, the deceptively simple term `XML support' implies compliance
with a number of related specifications.
The levels of support offered in the latest releases of Internet Explorer (version 6)
and Mozilla (version 1.5) are fairly comprehensive.The various types of functionality
incorporated includes:
Viewing of XML documents:
Each browser parses and presents the XML docu-
ment as a collapsible tree view. Parse errors are displayed with the position at which
they were encountered, which represents a useful feature for debugging purposes
when starting out with XML if a dedicated Integrated Development Environment
(IDE) is unavailable.
XML 1.0 and namespace standards:
The latest browsers support the official
XML specifications as outlined by W3C as well as namespace standards that facilitate
the distinguishing of XML vocabularies from different domains, by prefixing tag
names with unique qualifiers.
XML Document Object Model:
This exposes the XML document's elements and
attributes to scripting languages like ECMAScript and JavaScript. Previous versions
of Internet Explorer (IE 5 and 5.5) also sought to incorporate this functionality, but
based their implementation on a draft specification that was significantly different
from the final W3C recommendation.
Extensible Stylesheets (XSL):
A key area of browser support, and present in the
current versions. As with the DOM, Microsoft's earlier browsers incorporated support
for XSL based on a draft specification that would eventually be changed, so this
functionality is also incomplete in IE 5 and 5.5. XSL transformations offer Web
publishers the opportunity to traverse the XML document and `transform' the XML
`source tree' into an alternative-format `result tree'.The most common transformation
in terms of the Web is to take XML and turn it into XHTML, which browsers are
capable of rendering. XSLT (optionally combined with Cascading Style Sheets) has
therefore become the foremost presentation tool for XML content for the Web.
Access to this content is facilitated by using a browser which, by default, incorporates
an XSLT processor.
XML Data in HTML:
A proprietary Microsoft solution, and exclusive to Internet
Explorer, this allows developers to embed XML into HTML content using an
<XML> tag.This is often described as `XML Data Islands' and may incorporate
inline or linked content.
XML Schema and DTD:
Support for these two XML structural definition speci-
fications is offered by the current mainstream browsers.
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