IBM Version 5 manual Link and jump using XLink, XPointer, and XML Base

XML namespaces are used extensively in the XML arena, but, during the last two years, there has not been much technological advancement in this area.

2.5 Link and jump using XLink, XPointer, and XML Base

Anyone surfing the Internet knows the joys of moving from one document to another seemlessly. Links are easily embedded within one document to a pre-defined location another. As demands for linking functionality, more demands are required on the technology for more capabilities.

XLink, formerly known as XLL (the eXtensible Linking Language) provide advanced linking capabilities, while XPointer provides ways describing locations in XML documents. Xpointer is another layer built above XPath and is used to locating data and ranges of data. XBase complements XLink and XPointer by allowing developers to specify a document’s base URI. These can use the URI do point to documents using relative parts.

XML documents should have the capability of being easily linked to one another, and these links should be bi-directional. The basic unidirectional link is not enough for future needs. The W3C published a XML Linking Language Version 1 recommendation in June 2001.

In the future, we would need some, if not all of the following capabilities:

￿Multi-directional links: In today’s technology, we only have unidirectional links. The only way to return to the location of the called document is to select the Go Back button. With a multi-directional link, users could return to the original location through a link at the first link’s destination.

￿Link with multiple locations: There should be choice for different locations or documents from a single link.

￿Placing content inline from a linked document: Presently, we cannot present portions of two documents that are interlinked with one another.

The Xlink framework provides for a complex linking structures as will as unidirectional links. Besides specifying the relationships of the two resources to be linked, it can also associate meta data for that link.

The XLink type attribute may have one of the following attributes:

￿Title: A description for another linking element

￿Simple: A simple link

￿Extended: A multi-resource link. An extended attribute can have locator, arc, resource, and title as its child element types.

Chapter 2. Technologies in XML 25