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XML, the future
eXtensible Markup Language
Universal format for data.
What is it? Why to use it?
Xml is a tag based format as html, but it describes the content rather than the presentation of that content.
Tags may have attributes also, and that sounds as objects in programming languages.
Since tags describe the pure data, it is easy to search among them.
Any type of data may be described by Xml providing there is a grammar of the structure (the tags).
Defining the grammar
Before to write a xml document, you should write a Document Type Declaration. A DTD declares a grammar of tags, and a xml document is an instance of that grammar as an object is an instance of a class, or this is as a program for a language.
The dtd may be included into the xml document, or linked by an url.
Without the dtd, the xml document may be used but not checked for validity.
Dtd may be replaced by schemas. Schemas have the same syntax that xml (Dtd use a different one), allow custom datatypes and have lots or predefined ones.
How to use the xml code
To use a xml document, you need for a parser that validates the structure of the document.
The definition of a such parser is given by the document object model (DOM).
Implementations of Dom exists for C++, Java and other programming languages.
Producing a document for users
Xml, as html has its stylesheet, named XSL that provides rules to tranform xml into another format (html for example).
Using xml documents
Tools has been defined (by the W3C) to access xml documents. Xlink define links inside xml documents. Xpath defines how to access specific elements. Xupdate defines how to change xml elements
Beyond simple data documents
The power of Xml goes beyond simple data storage, various other usages are emerging.
Turning xml into executable is the last trend of the market. Jelly is a mean to do that.
SVG defines graphic elements to produce scalable images, and replace the flash format.
XUL is a set of elements to build graphical user interface, it is used by the Mozilla browser. | |
Extensions for xml
DOM (Document Object Model)
Api to dynamically access and change either the content or the structure of xml documents. It is a platform and language independent interface.
XSL (eXtensible Stylesheet Language)
A xsl is a set of transformation rules, allowing to map structures with choosen elements and attributes in xml documents.
A set of rules for translating a xml document into html is the best example of a xsl, but we can translate xml into anything.
The difference between xsl and XSLT is that xsl produces any format while xslt convert from xml to another xml document.
XLink (XML Linking Language)
A language (that uses xml syntax), that can be inserted into xml resources to describe unidirectional hyperlinks (like html) or more complexe multi-ended and typed links. Xlink may be used with XPointer.
XPointer (XML Pointer Language)
A language that can address selected elements in the internal structures of xml documents. It is based on the XPath language.
DCD (Document Content Description for XML)
A schema, as a dtd, describes the grammar of tags for validating xml documents.
DCD is a language that provide a structural schema facility (using xml syntax), which replaces the functions of the dtd to describe constraints on tags and content of xml documents. Additionally it also describes datatypes and relationships in databases.
DCD incorporates a subset of XML-Data, and is an RDF (Resource Description Framework) vocabulary.
SVG (Scalable Vector Graphics)
An api that describes graphical objects, that can be dynamically interfaced with JavaScript to make animations. A Svg document currently may be displayed as a web page providing the browser has the correct plug-in.
XQuery (Xml Query)
Specification to turn xml documents into databases. |
Main tools and tutorials for xml
Developers Works The site of IBM dedicated to xml. You can download XML4C, the parser and other tools.
Apache From Apache, you can download these tools:
Xerces the XML parser. Implements DOM, SAX and schema. (C++, Java).
Batik the SVG viewer and converter (Java only).
Xalan implements XSLT and XPath (C++, Java).
Forrest converts XML into HTML or PDF, for web site creation.
Cocoon is a XML server.(Java).
Xindice is intended to builds XML databases. (Java, Not finished).
W3C
XPath Language for query on xml documents.
XQL Query language on xml.
Mozilla
XUL (XML User Interface Language). Is a GUI in XML for applications.
Sourceforge
Jaxen is a Xpath processor. (Java).
Lagoon Design the sitemap of your site in xml, the files in xml or html, build the site with lagoon and send the html result on the server. For some Windows rename xxx.cmd to xxx.bat. (Java for the tool) |
More. Tools
SVG Replaces Flash for graphical web sites.
Majix Convert a RTF file into XML.
Xml Software This site list a lot of tools, but too often commercial. |
More infos on Xml
Xml.com Articles.
Xml Hack News. |
 
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