# 13. XHTML Hypertext Attributes Module

Contents

This section is normative.

The Hypertext Attributes Module defines the Hypertext attribute collection. This collection allows an element to be the start point of a hypertext link to a remote resource.

## 13.1. Hypertext Attribute Collection

cite = URI
  The value of this attribute is a URI that designates a source document or message. This attribute is intended to give further information about the element's contents (e.g., the source from which a quotation was borrowed, or the reason text was inserted or deleted). User Agents MUST provide a means for the user to actuate the link.

  Example

      cite="comments.html"

href = URI
  This attribute specifies a URI that is actuated when the element is activated.

  Actuation occurs as the default action of a [DOM] DOMActivate event for the element on which the attribute occurs (for instance as the result of the user clicking on the associated element). If elements contained within an element using an @href also use an @href attribute, the User Agent must provide a mechanism for actuating any of these "nested" URIs.

  Example

      <abbr href="http://www.w3.org/" title="World Wide Web">WWW</abbr>
      <li href="contents.xhtml">contents</li>
      <a href="http://www.cwi.nl/~steven/amsterdam.html">Amsterdam</a>
      <quote href="hamlet.xhtml#p2435">To be or not to be</quote>
      <var href="#index_ninc">ninc</var>

hreflang = LanguageCodes

  This attribute specifies the primary language of the resource designated by @href. At its most general, it is a comma-separated list of language ranges with optional accept parameters, as defined in section 14.4 of [RFC2616] as the field value of the Accept-Language request header.

  In its simplest case, this is just a language code, such as "nl", but it may also contain variant specifications such as "en-gb".

  The user agent must use this list as the field value of the `accept-language` request header when requesting the resource using HTTP.

  If this attribute is not present, the user agent must use its default value of the accept-language request header.

  Example

      <p href="http://www.w3.org/2003/06/semantictour-pressrelease"
         hreflang="fr">
         The press release in French
      </p>

hrefmedia = MediaDesc
  This attribute indicates the type(s) of media to which to make available the content referenced by the associated @href URI.

  Example

      <p href="http://www.example.com/forPrinters.html"
         hrefmedia="print">
         A printable version of this page.
      </p>

hreftype = ContentTypes
  This attribute specifies the allowable content types of the relevant @href URI. See ContentTypes for details of how it is used.

  Example

      <p href="http://www.w3.org"
         hreftype="text/html,application/xhtml+xml">
         The W3C Home Page
      </p>

nextfocus = IDREF
  This attribute specifies an IDREF of an element in the current document that will receive focus when the user requests that the user agent navigate to the next element that can receive focus.

  The sequence of focusable elements is called the document's navigation order. The navigation order defines the order in which elements will receive focus when navigated by the user. The navigation order may include elements nested within other elements.

  When a document is first loaded, a user agent must do the following:

  1. If a document is loaded using a URI that includes a reference to a fragment identifier (such as `book.html#chapter5`)
     1. If the fragment reference identifies an element in the document, the user agent must ensure that navigation starts at the beginning of that element.
     2. If the referenced element is focusable, that element receives focus.
     3. If the fragment reference does not resolve in the document, the user agent must ensure navigation starts at the beginning of the document.
  2. If there is no reference to a fragment identifier when the document is loaded:
     1. If the root element of the document has a @nextfocus attribute, and the element referred to by the attribute is focusable, the element must receive focus. The user agent must ensure the beginning of the element is visible on the display.
     2. If the root element has no @nextfocus attribute, no element receives initial focus. The user agent must ensure navigation starts at the beginning of the document.
  3. If the user has moved away from the initial navigation point of a document (e.g., through using page up and page down or by changing focus), refreshing the document should result in the user's navigation location being preserved.

  In the event no element in the document has focus, when the user requests the next focusable element, that element must be the next focusable element forward from the current navigation point in document order. If there are no focusable elements before the end of the document, focus shifts to the first focusable element in document order. If a document has no focusable elements, then no element receives focus.

  Once a focusable element in the document has focus, upon requesting that focus change to the next focusable element, the user agent MUST follow these rules when determining where focus is next set:

  1. The next focus of an element without a @nextfocus attribute is the next focusable element in document order. If there are no remaining focusable elements in document order, the next focus must be on the first focusable element in document order.
  2. The next focus of an element with a @nextfocus attribute is the element referenced by that attribute if it is focusable, otherwise the next focus of that element.

  Regardless of the way in which an element receives focus, if the element is not currently visible on the user agent's display, the display must be updated so that the element is visible.

  The following example would allow the links to be navigated in column order (without the use of `nextfocus` they would be navigated in document, i.e. row, order):

  Example

      <table>
      <tr><td id="a" href="nw" nextfocus="b">NW</td>
          <td id="c" href="ne" nextfocus="d">NE</td></tr>
      <tr><td id="b" href="sw" nextfocus="c">SW</td>
          <td id="d" href="se">SE</td></tr>
      </table>

  Navigation keys. The actual key sequence that causes navigation or element activation depends on the configuration of the user agent (e.g., the "tab" key might be used for navigation and the "enter" key or "space" key used to activate a selected element).

prevfocus = IDREF
  This attribute specifies an IDREF of an element in the current document that will receive focus when the user requests that user agent navigate to the previous element that can receive focus.

  In the event no element in the document has focus, when the user requests the previous focusable element, that element must be the next focusable element backward from the current navigation point in document order. If there is no such focusable element back to the start of the document, focus shifts to the last focusable element in document order. If a document has no focusable elements, the behavior is unspecified.

  Once a focusable element in the document has focus, upon requesting that focus change to the previous focusable element, the user agent must do the following:

  1. If the focused element has a @prevfocus attribute that references a focusable element, focus is moved to that element.
  2. Otherwise, focus shifts to the previous focusable element in document order.
  3. If there are no previous focusable elements in document order, focus shifts to the last focusable element in document order.

  Regardless of the way in which an element receives focus, for visual user agents, if the element is not currently visible on the user agent's display, the display must be updated so that the element is visible.

target = HrefTarget
  This attribute identifies an environment that will act as the destination for a resource identified by a hyperlink when it is activated.

  This specification does not define how this attribute gets used, since that is defined by the environment that the hyperlink is actuated in. See for instance XFrames [XFRAMES]. However, values of this attribute that begin with the character '`_`' are reserved.

  Example

      <a href="home.html" target="main">Home</a>

xml:base = URI
  This attribute specifies the base URI from which to resolve relative URIs. It is normatively defined in [XMLBASE]. Any relative URI used on an element that uses this attribute, or on an element contained within an element that uses this attribute, must be resolved relative to the base URI defined by this attribute.

  An element inherits URI base information according to the following order of precedence (highest to lowest):

  1. The @xml:base attribute set for the element itself.
  2. The closest parent element that has the @xml:base attribute set (i.e., the @xml:base attribute is inherited).
  3. The HTTP "Content-Location" header (which may be configured in a server).
  4. The location of the document itself.

  Example

      See:
      <ul xml:base="http://www.w3.org">
      <li href="/" src="Icons/w3c_home">The W3C home page</li>
      <li href="/TR">The W3C Technical Reports page</li>
      <li href="/Markup">The HTML home page</li>
      <li href="/Markup/Forms">The XForms home page</li>
      </ul>

Implementations: RELAX NG, XML Schema