Xlinks

Linking in XML is similar to links in HTML. In HTML the <A> tag is used to achieve linking. Whenever a browser encounters an anchor tag <A> in an HTML document it understands that the tag links to an external document. In the case of an XML document, we have to indicate to the browser that the tag is a linking tag and also the type of the link. XLink provides a framework for creating both basic uni directional links and more complex linking structures. It allows XML documents to:

Assert linking relationships among more than two resources, Associate metadata with a link and Create link databases that reside in a location separate from the linked resources

For example let us consider the following document:

<testlink>
<block>Connects to home page
<mylink href="http://www.microsoft.com/homt.html">
</mylink>
</block>
</testlink>

XLink Attributes

href

The attribute which supplies the data that allows an XLink application to find a remote resource is href. It can be used on simple type elements, and is required on locatortype elements. The value of the href attribute must be a URI reference.

In line

Most of the links are in line and so they take in a value of true. An out of line link takes false value of false. An out of line link is discussed later in this chapter.

role

This attribute is used to indicate the meaning of the link to the browser. The value of the role attribute is used to provide information to the user about the destination of the link.

title

The title attribute is used to describe the function of a link's remote resource in a human readable fashion. The title attribute can be displayed whenever a mouseover event takes place.

show

The show attribute can take in four values namely replace, new, embed and undefined. If the show attribute takes a value of replace, then the new resource replaces the old. If the value is new, then a window is opened. If the value is embed, then the new resource will be embedded in the old. If an application encounters a value of the show attribute that it does not recognise, or the absence of a value, it treats the value as "undefined".

actuate

This attribute is used with extended links. It can take in three two values namely onLoad, onRequest, and undefined. If the attribute value is onLoad then the application should traverse to the ending resource immediately on loading the starting resource. If the attribute value is on Request then the application should traverse from the starting resource to the ending resource only on a post loading event triggered for the purpose of traversal. If the attribute value is undefined, then the behaviour of the application traversing to the ending resource is unconstrained by this specification.

behaviour

The value of the behaviour describes what can happen when the link is traversed. The user may be presented with a selection list or a new window, etc.

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