Next Generation HTML: Linking Efforts
June 7th 1998
You may have noticed that there is no linking spec on the extreme
left. This is because the linking mechanism that is so fundamental
to the Web is relatively simple; it is described in the
Links section of the HTML specification and in
several RFC's (Internet Requests For Comments)
concerning URIs. In the publishing world, however, very complex
and powerful linking mechanisms have existed for years:
Text Encoding Initiative (TEI),
an "international project to develop guidelines for
the preparation and interchange of electronic texts for scholarly
research", and
Hypermedia/Time-based Structuring Language (HyTime),
an effort of ISO (the International Organization for
Standardization) and IEC (the International Electrotechnical
Commission).
XML Linking Language
(aka XLink) and
XPointer
are the evolving Web compromises, based largely on
TEI Extended Pointers.
As we can tell from the Big Picture, XLink and XPointer are
presently Working Drafts. XLink describes how simple
uni-directional links a la HTML) as well as more sophisticated
multi-directional and typed links can be added to XML documents.
The related
XPointer Working Draft
"provides for specific reference to elements, character
strings, and other parts of XML documents, whether or not they bear
an explicit ID attribute."
XML Applications (Vocabularies)
As stated earlier, the right side of the diagram depicts specs
that are all related to XML. In a sense, they are all XML
applications in that they rely on XML syntax. Some are
specialized markup languages, also called XML vocabularies, such
as MathML (Mathematical Markup Language), a W3C recommendation,
SMIL (Synchronized Multimedia Integration Language), a Proposed
Recommendation, and PGML (Precision Graphics Markup Language),
WIDL (Web Interface Definition Language), and CDF (Channel
Definition Format), three W3C Notes. Others are more like
applications layered on top of XML, such as the RDF (Resource
Description Format), Metadata efforts,
PICS 2.0 ( Platform for Internet
Content Selection) and
P3P (Platform for
Privacy Preferences).
However, the distinction between these two groups may not be
terribly significant.
Next Generation HTML: Style Sheets
Next Generation HTML: The Big Picture
Next Generation HTML: Netscape and Microsoft
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