XML.com: An Introduction to XML Linking

Published on XML.com http://www.xml.com/pub/a/98/06/xlink/av.html
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An Introduction to XML Linking

June 10, 1998

A Talk by Eve Maler on XLL

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Eve Maler of Arbortext is co-editor of the XML Linking Language (XLL) specification, which is currently a working draft at the W3C. In this talk, Maler explains the goals of XLL and how it enables new applications and solves old problems. This audio presentation is an edited excerpt of her talk at Seybold Seminars/NY.

Update: While Maler comments in this talk that the name of the linking specification was in flux, and refers to it as XLL and XLink, the working group has decided to continue using XLL.

Outline

What XLL Enables

Bidirectional linking
Filtered views of data
Persistent links that have semantics attached to them
Dynamic document assembly
Create links from documents you can't edit
Publish dynamic updates or software patches
Support annotations
Manage links so that they don't break
Establish links as first-class citizens.

The XLL Specification

First called XLink, then XML-Link and now XLL.
XLL may become its own working group at the W3C.
Co-editors of the specifications are Eve Maler and Steve DeRose
Based on SGML, HyTime and the Text Encoding Iniative(TEI).

Goals of XLL

To provide advanced linking constructs

Scalable
Maintainable

Two Components of XLL

X-Link
XML linking is the ability to link to something that's interesting to you.
X-Pointer
XML Pointer adds advanced addressing into the XML Document structure.

X-Pointer

X-Pointer is a language for pointing into the sub-parts of a document. HTML limits pointing to things in a document that have an ID or are named using the Anchor tag. X-pointers are used with URLs.

X-Pointer Syntax

Location pointers are a series of steps to define a path to a particular place in a document. It's like being given directions to a house.

Advantages of X-Pointer

Small syntax
More robust against change
X-Pointers operate on tree nodes.

Features of XLL

A language that allows you to invent your own link elements.
Allows you to create link databases
Specify traversal behavior

Basic link types

There are two basic link types.

Inline links that live at point where link is initiated.
Out-of-line links that live in a link databases.

Utilizes the power of databases for linking.

XML Spec

The current draft of the XML Spec is available at the W3C: XLL Working Draft