W3C/Related Articles

See also changes related to W3C, or pages that link to W3C or to this page or whose text contains "W3C".

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Parent topics

• World Wide Web [r]: A global collection of information presented in the form of documents hosted on networked computers and available to the public. ^[e]

Subtopics

• Cascading Style Sheets [r]: A format designed by the W3C for describing the presentation, layout and other design choices of a document on the Web. ^[e]
• HTML [r]: A set of tags for marking up the content of a web page into distinct sections. ^[e]
• HTTP [r]: Network protocol on which the World Wide Web is based. ^[e]
• Hypertext [r]: A means of combining human-readable information with metadata about the information, with special reference to the ability to "link" or "jump" to subjects of interest; invented by Ted Nelson at Project Xanadu in the 1960s and first deployed as Apple Computer's product, Hypercard; ancestor of the Hypertext Markup Language and the World Wide Web ^[e]
• Resource Description Framework [r]: W3C standard for exchange of metadata about Web resources. ^[e]
• Semantic Web [r]: Tim Berners-Lee's concept of a "web of knowledge", whereby web-based document contents would be annotated and classified so that computers can parse the classifications and provide search results based on the semantic information (what the content means), rather than simply on matching of text strings. ^[e]
• SVG [r]: a modular XML-based markup language for describing static, interactive, and animated two-dimensional vector graphics ^[e]
• XHTML [r]: a form of web page markup language which is similar to HTML but adheres to stricter syntax rules, being based on XML ^[e]
• XML [r]:
  

See also changes related to W3C, or pages that link to W3C or to this page or whose text contains "W3C".

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XML (eXtensible Markup Language) is a platform-independent, human-readable format for representing data. It was released as a W3C Recommendation in November 1998 and, perhaps because of its platform independence and readability both by humans and software, obtained immediate acceptance. Today, XML is in widespread use across the World Wide Web, especially for sending data between computers and for serializing data to disk, and most computer programming languages include support for it. XML is one of several wire formats used in Ajax (Asynchronous Javascript And Xml), the background interaction of a web page with programs residing elsewhere on a network.

XML Specification and Origin

XML is a subset of the Standard Generalized Markup Language, or SGML (ISO8879-1986). XML's specification first emerged in 1996 through the efforts of the XML Special Interest Group and the SGML Editorial Review Board, chaired by John Bosak of Sun Microsystems. The group, also known as the XML Working Group, laid out the following set of guidelines or design goals for XML:

1. XML shall be straightforwardly usable over the Internet.
2. XML shall support a wide variety of applications.
3. XML shall be compatible with SGML.
4. It shall be easy to write programs which process XML documents.
5. The number of optional features in XML is to be kept to the absolute minimum, ideally zero.
6. XML documents should be human-legible and reasonably clear.
7. The XML design should be prepared quickly.
8. The design of XML shall be formal and concise.
9. XML documents shall be easy to create.
10. Terseness in XML markup is of minimal importance.

Notably missing from the above list is efficiency. XML is plain text and can be verbose, and in applications where speed is everything, a different data representation may be preferred.

Grammar and Definitions

This section contains a brief over view of the components that define XML, for a more in-depth examination of those components read the individual sections under the heading Structure

Prolog - A prolog is a sort of 'announcement' to the XML parser as to what version the following set of XML objects is written in. The prolog also contains other information pertinent to the XML document (discussed later.)

<?xml version="1.0" standalone="no" ?>

Tag - A tag denotes the beginning, end, or existence of an XML object. They consist of the < character followed by the name of the tag, and, in the case of an opening tag, just a > at the end. The exception is with end tags and single tags. End Tags always have a < then a forward slash before the name of the tag with a > at the end. Single tags always have a space after the name of the tag followed by a forward slash and then end with the >.

Example

<ninja>
    <inventory>
        <nunchucks />
        <cookies />
    </inventory>
</ninja>

Element - An element is an XML object composed of a start tag and a stop tag or a single tag.

Example

<?xml version="1.0" standalone="no" ?>
<family>
    <member>
        <name>dad</name>
        <favorite-food>pancakes</favorite-food>
        <favorite-animal>wombats</favorite-animal>
    </member>
</family>

Document - A document is any XML object that contains a prolog and one or more elements excluding the root element.

<?xml version="1.0" standalone="no" ?>
<root-element>
    <lots-of-elements>
    ...
    </lots-of-elements>
</root-element>

Structure

Prolog

The XML prolog is a mandatory object present at the beginning of the document.

<?xml version="###" {encoding="???" standalone='y/n'} ?>

version equals the version of XML the document was written to.

(Optional) encoding equals the character codebook the document was written to. The default is UTF-8. The character encoding declaration must be written using latin characters only.

EncName    ::=    [A-Za-z] ([A-Za-z0-9._] | '-')* 

The encoding name must begin with an alphabetic character and all other characters must be alphanumeric, the underscore ( _ ), the decimal ( . ), or a dash ( - ).

(Optional) standalone is either yes or no. Yes in the instance that the XML document does not have an external DTD or Schema. No if the XML document does have an external DTD or Schema.

Elements

An element is an XML object defined by the accompanying DTD or Schema that is described by the use of tags, parsed text, attributes, and entities. An element may consist of a start tag and a end tag or a single tag.

<?xml version="1.0" standalone="no" ?>
<army>
    <ninja name="woody">
        <inventory>
            <nunchucks count="2" />
            <cookies count="15" />
        </inventory>
    </ninja>
</army>

In this case, <army> represents a root element that contains a series of elements, in this example the element shown is a <ninja>. A ninja has an inventory that contains a certain number of nunchucks and a certain number of cookies. The number of cookies and nunchucks are defined by the attribute count. Note, the attribute values are in quotation marks, all well formed XML documents have their attributes quoted in that fashion either with single quotes ' or double quotes ".

External links

• http://www.w3schools.com/xml/

Related Technologies

• Extensible Stylesheet Language
• Extensible Stylesheet Language Transformations
• Extensible Stylesheet Language Formatting Objects
• Really Simple Syndication
• Resource Description Framework
• XPath
• XQuery
• XForms
• XPointer
• XLink
• Web Services Description Language ^[e]

Other related topics

• Tim Berners-Lee [r]: British software developer famous for creating the World Wide Web. ^[e]

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