xlinks

XLinksXLinks

Praveen Polishetty

Contents :

• XLink Capabilities• XLink Concepts• XLink Core Properties• XLink Semantic Properties• XLink Behavior Properties• XLink Traversal Properties• Types of XLinks• Summary• References

• It is an XML linking language which allows for elements to be inserted into XML documents in order to create and describe links between resources.

Capabilities of XLinks:

• Assert linking relationships among more than two resources.

• Associate metadata with a link.• Express links that reside in a

location separate from the linked resources.

XLink Concepts:

• Links and Resources• Arcs Traversal and Behavior• Resources in relation to the

physical location of a linking element.

Links and Resources:

• LINK : It is an explicit relationship between resources or portions of resources.

• Resource : It is any addressable unit of information or service.

Arcs Traversal and Behavior:

• Arc : Information about how to traverse a pair of resources, including the direction of traversal and possibly application behavior information.

• Traversal : Using or following a link for any purpose

Resources in relation to the physical location of a linking element:• Local Resource : It is an XML element that

participates in a link by virtue of having as its parent, or being itself, a linking element

• Remote Resource : Any resource or resource portion that participates in a link by virtue of being addressed with a URI reference

XLink Core Properties:

• XLink element Type attribute(type)

• XLink element Locator attribute(href)

XLink element Type attribute (type):

• XLink:type attribute indicates the type of the link:

• value simple simple link • value extended extended link

XLink element Locator attribute (href):

• XLink:href this is the only locator attribute, and its value is an URI Reference.

XLink Semantic Properties:

Those are placeholders for application semantic:

• XLink:title is designed to provide human-readable text describing the links, simple links must use an attribute while extended links must use an element.

• XLink:role is an attribute containing a qualified name used to describe the function of the link's or locator's content.

XLink Behavior Properties:

• Attributes are– show– actuate

Show Attribute:

• XLink:show indicate expected behaviour on traversal effect:

• value embed the link target should be included like <IMG>

• value new the link target should create a new rendering, like opening a new window.

• value replace the link target should replace the resource containing the link, like <A> in most cases.

Actuate attribute:

• XLink:actuate indicate expected triggering of link:

• value auto indicate at link detection time, like <IMG> if auto loading of images is turned on.

• value onRequest indicate activation at user's request, like <A>

XLink Traversal Properties:

Attributes:• Label• From• To

Types of Links:

• Simple –An outbound link with exactly two participating resources

• Extended–Links that have arbitrary numbers of participating resources

Extended Links:

View:

Advanced Features:

• Multiple sources and targets using XLink:locator elements

• Multiple actuation possible using XLink:arc elements

• Multiple XLink:title elements.

XLink :Extended• xlink:extended element <?xml version="1.0"?> <WEBSITE> <xlink:extended

xmlns:xlink="http://www.w3.org/XML/XLink/0.9">  </xlink:extended> </WEBSITE> • An element of arbitrary type like COMPOSER or TEAM that has

xlink:type attribute with the value extended <?xml version="1.0"?> <WEBSITE xmlns:xlink="http://www.w3.org/XML/XLink/0.9" xlink:type="extended">  </WEBSITE>

Examples of Extended Links:

Locator toRemoteresource





Extended

Contd…



Locator toRemote resource



ExtendedLocal

ResourceLocal

resource

Extended Links:

The extended type element may contain any of the following:

• Locator• Arc• Title• Resource

Extended Links:

• Local Resources (resource type element)

• Remote Resources (Locator type element)

• Traversal Rules (Arc type Element)

Local Resources:

An extended link indicates its participating local resources by means of special sub elements that appear inside the extended link. An entire sub element, together with all of its contents, makes up a local resource.

Remote Resources:

An extended link indicates remote resources that participate in it by means of locator elements.

Traversal Rules:

An extended link may indicate rules for traversing among its participating resources by means of a series of optional arc elements.

Simple links:

View:

Source

Link Target

Xlink:Simple• <xlink:simple xmlns:xlink= “http://www.w3.org/XML/Xlink/0.9” href="footnote7.xml"> <FOOTNOTE>7</FOOTNOTE> </xlink:simple>• <xlink:simple xmlns:xlink=“http://www.w3.org/XML/Xlink/0.9” href="http://www.interport.net/~beand/"> <COMPOSER>Beth Anderson</COMPOSER> </xlink:simple>• <IMAGE> <xlink:simple xmlns:xlink="http://www.w3.org/XML/XLink/0.9" href="logo.gif"/> </IMAGE> If used in a valid document, xlink:simple must be declared <!ELEMENT xlink:simple ANY> <!ATTLIST xlink:simple xmlns:xlink CDATA #FIXED "http://www.w3.org/XML/XLink/0.9" href CDATA #REQUIRED >

Example of Simple Link:

Simple

Localresource


Localresource

Limitations of Simple Links:

• Supplying arbitrary numbers of local and remote resources

• Specifying an arc from its remote resource to its local resource

• Associating a title with the single hardwired arc

• Associating a role or title with the local resource

• Associating a role or title with the link as a whole

Summary:• Simple links behave much like HTML links, but they are not restricted

to a single <A> tag.• Link elements are identified by xlink:type attributes.• Simple link elements are identified by xlink:type attributes with the

value simple. The xlink:simple element is also a simple link.• Link elements can describe the resource they're linking to with title

and role attributes.• Link elements can use the show attribute to tell the application how

the content should be displayed when the link is activated, for example, by opening a new window.

• Link elements can use the actuate attribute to tell the application whether the link should be traversed without a specific user request.

• Extended link elements are identified by xlink:type attributes with the value extended. The xlink:extended element is also an extended link.

• Extended links can contain multiple locators and arcs. Currently, it's left to the application to decide how to choose between different alternatives

Contd….• Locator elements are identified by xlink:type attributes with the value

locator. The xlink:locator element is also a locator element.• A locator element has an href or xlink:href attribute whose value is the URI

of the resource it locates.• Arc elements are identified by xlink:type attributes with the value arc. The

xlink:arc element is also an arc element.• Arc elements have from and to attributes of IDREF type that identify to the

locator elements they connect.• Arc elements may have show and actuate attributes to determine when and

how traversal of the link occurs.• An extended link group element contains a list of links that connect a

particular group of documents.• An extended link group element is identified by an xlink:type attribute with

the value group. An xlink:group element is also an extended link group element.

• An out of line link is an XLink (most commonly an extended XLink) that is not part of any of the documents it connects. Instead, the links are stored in a separate linking document.

• An extended link document element is identified by an xlink:type attribute with the value document. An xlink:document element is also an extended link document element.

References:

• www.w3.org• www.unc.edu• www.ibiblio.org/xml/ • www.Xml.com

Thank you

Email:[email protected]

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