Grass Valley iControl Services Gateway - Manual (Page 25)

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Appendix B The XML Technologies Family
There is XML 1.0 , the specification that defines what "tags" and "attributes" are, but around XML 1.0,
there is a growing set of optional modules that provide sets of tags & attributes, or guidelines for specific
tasks. There is, e.g.,
Xlink (still in development as of November 1999), which describes a standard way
to add hyperlinks to an XML file. XPointer & XFragments (also still being developed) are syntaxes for
pointing to parts of an XML document. (An XPointer is a bit like a URL, but instead of pointing to
documents on the Web, it points to pieces of data inside an XML file.)
CSS , the style sheet language, is
applicable to XML as it is to HTML. XSL (autumn 1999) is the advanced language for expressing style
sheets. It is based on XSLT , a transformation language that is often useful outside XSL as well, for
rearranging, adding or deleting tags & attributes. The DOM is a standard set of function calls for
manipulating XML (and HTML) files from a programming language. XML Namespaces is a specification
that describes how you can associate a URL with every single tag and attribute in an XML document.
What that URL is used for is up to the application that reads the URL, though. (
RDF , W3C's standard for
metadata, uses it to link every piece of metadata to a file defining the type of that data.) XML Schemas 1
and 2 help developers to precisely define their own XML-based formats. There are several more
modules and tools available or under development. Keep an eye on W3C's technical reports page .
XML Benefits
By choosing XML as the basis for some project, you buy into a large and growing community of tools
(one of which may already do what you need!) and engineers experienced in the technology. Opting for
XML is a bit like choosing SQL for databases: you still have to build your own database and your own
programs/procedures that manipulate it, but there are many tools available and many people that can
help you. And since XML, as a W3C technology, is license-free, you can build your own software around
it without paying anybody anything. The large and growing support means that you are also not tied to a
single vendor. XML isn't always the best solution, but it is always worth considering.