Connections between documents and parts of documents

HTML, Hyperlinks <A href="hyperlink.html">About</a>

XML, XLink, XPointer, XPath and XBase

Linking with XLinks and XPointers

XLink

How one document links to another document

XML Linking Language (XLink) Version 1.0 W3C Recommendation 27 June 2001 http://www.w3.org/TR/xlink

XPointer

Specify location inside a document (XPath)

XML Pointer Language (XPointer) Version 1.0 W3C Recommendation 11 September 2001 http://www.w3.org/TR/xptr

XML Linking Language

Framework for creating

Basic unidirectional links
Complex linking structures
Assert linking relationships among more than two resources
Associate metadata with a link
Express links that reside in a location separate form the linked resources

XLink Markup Design

XLink namespace: http://www.w3.org/1999/xlink

<my:crossReference
    xmlns:my="http://example.com/"
    xmlns:xlink="http://www.w3.org/1999/xlink"
    xlink:type="simple"
    xlink:href="students.xml"
    xlink:role="http://www.example.com/linkprops/studentlist"
    xlink:title="Student List"
    xlink:show="new"
    xlink:actuate="onRequest">
    Current List of Students
</my:crossReference>

XLink Elements and Attributes

Extended links

Full XLink functionality
Complex structure
Point to remote resources
Contain local resources
Specify arc traversal rules
Specify human-readable resource
Special semantics for finding linkbases

Simple links

Shorthand syntax for a common kind of link
Outbound link with exactly two resources

Extended links attributes

xlink:type "extended"
xlink:role
xlink:title

Extended links elements (title | resource | locator | arc)*

title

xlink:type "title"

resource

xlink:type "resource"
xlink:role
xlink:title
xlink:label

locator

xlink:type "locator"
xlink:href
xlink:role
xlink:title
xlink:label

arc

xlink:type "arc"
xlink:arcrole
xlink:title
xlink:show "new", "replace", "embed", "other", "none"
xlink:actuate "onLoad", "onRequest", "other", "none"
xlink:from
xlink:to

Simple links attributes

xlink:type "simple"
xlink:href
xlink:role
xlink:arcrole
xlink:title
xlink:show "new", "replace", "embed", "other", "none"
xlink:actuate "onLoad", "onRequest", "other", "none"

xlink:type attribute

"simple" Creates a simple link

"extended" Creates an extended link

"locator" Creates a locator link that points to a resource

"arc" Creates an arc with multiple resources and various traversal paths

"resource" Creates a resource link, which indicates a specific resource

"title" Creates a title link. Such elements are useful for internationalizetion purposes.

The locator xlink:href attribute

Supply the data to find a remote resource
Specify a document (URI) and an XPointer

<CLASS_SLIDE xmlns:xlink="http://www.w3.org/1999/xlink"
  xlink:type="simple"
  xlink:show="new"
  xlink:href="http://www.cs.rpi.edu/~puninj/XMLJ/classes.xml#        
  				xpointer(/child::*[position()=8]/child::*[position()=first()])">
  XLinks and XPointers
</CLASS_SLIDE>

Semantic attributes xlink:role, xlink:arcrole and xlink:title

Optional attributes

xlink:title - Human-readable description

xlink:role, xlink:arcrole - URI reference identifies some resource that describes the intended property

<CLASS_SLIDE xmlns:xlink="http://www.w3.org/1999/xlink"
  xlink:type="simple"
  xlink:show="new"
  xlink:role="http://www.cs.rpi.edu/~puninj/XMLJ/slideroles"
  xlink:title="XLinks and XPointers"
  xlink:href="http://www.cs.rpi.edu/~puninj/XMLJ/classes.xml#        
  				xpointer(/child::*[position()=8]/child::*[position()=first()])">
  XLinks and XPointers
</CLASS_SLIDE>

Behavior attribute: xlink:show

"replace" Replaces the current resource in the same window
"new" Opens a new display area, such as a new window, to disply the new resource
"embed" Embeds the linked-to resource in the current resource
"other" The application should look for other markup present in the link to determine the appropiate behavior
"none" No other markup is present to help the application determine the appropiate behavior

Behavior attribute: xlink:actuate

"onRequest" Indicates that the link should be traversed only on the user'srequest
"onLoad" Indicates that the link should be traversed when the document or resource is loaded
"other" The application should look for other markup present in the linkto determine the appropiate behavior
"none" No other markup is present to help the application determine the appropiate behavior

Locator-type element

<!ELEMENT person EMPTY>
<!ATTLIST person
  xlink:type      (locator)       #FIXED "locator"
  xlink:href      CDATA           #REQUIRED
  xlink:role      CDATA           #IMPLIED
  xlink:title     CDATA           #IMPLIED
  xlink:label     NMTOKEN         #IMPLIED>
                
<!ELEMENT course EMPTY>
<!ATTLIST course
  xlink:type      (locator)       #FIXED "locator"
  xlink:href      CDATA           #REQUIRED
  xlink:role      CDATA           #FIXED "http://www.example.com/linkprops/course"
  xlink:title     CDATA           #IMPLIED
  xlink:label     NMTOKEN         #IMPLIED>

<person xlink:href="students/patjones62.xml"
        xlink:label="student62"
        xlink:role="http://www.example.com/linkprops/student"
        xlink:title="Pat Jones" />
<person xlink:href="profs/jaysmith7.xml"
	xlink:label="prof7"
	xlink:role="http://www.example.com/linkprops/professor"
	xlink:title="Dr. Jay Smith" />
<course xlink:href="courses/cs101.xml"
	xlink:label="CS-101"
	xlink:title="Computer Science 101" />

Resource-type element

<!ELEMENT gpa ANY>
<!ATTLIST gpa
  xlink:type      (resource)      #FIXED "resource"
  xlink:role      CDATA           #FIXED "http://www.example.com/linkprops/gpa"
  xlink:title     CDATA           #IMPLIED
  xlink:label     NMTOKEN         #IMPLIED>

<gpa xlink:label="PatJonesGPA">3.5</gpa>

Traversal Attributes xlink:from, xlink:to, xlink:label

xlink:from What resource an arc comes from

xlink:to What resource an arc goes to

xlink:label Label of a resource of locator element

If a value is supplied for a xlink:from or xlink:to attribute, it must correspond to the same value form some xlink:label attribute on a locator or resource element

<!ELEMENT go EMPTY>
<!ATTLIST go
   xlink:type      (arc)           #FIXED "arc"
   xlink:arcrole   CDATA           #IMPLIED
   xlink:title     CDATA           #IMPLIED
   xlink:show      (new|replace|embed|other|none)	#IMPLIED
   xlink:actuate   (onLoad|onRequest|other|none)	#IMPLIED
   xlink:from      NMTOKEN         #IMPLIED
   xlink:to        NMTOKEN         #IMPLIED>

<go xlink:from="CS-101"
    xlink:arcrole="http://www.example.com/linkprops/auditor"
    xlink:to="student62"
    xlink:show="replace"
    xlink:actuate="onRequest"
    xlink:title="Pat Jones, auditing the course" />

XPointers

XPointer is build on top of the XML Path Language. These extensions allow:

Be used in URI references to address into resources
Address points and ranges as well as whole nodes
Locate information by string matching


		xlink:href="http://www.cs.rpi.edu/~puninj/XMLJ/classes.xml#
		xpointer(/child::*[position()=8]/child::*[position()=first()])">

XPointers extend XPaths

Enable to select "points" and "ranges"
Extends the idea of "nodes" into "locations
"node sets" become "location sets"


axis::node_test[predicate]

For example:


child::STUDENT[position() = 3]

XPointer Axes

ancestor
ancestor-or-self
attribute
child
descendant
descendant-or-self
following
following-sibling
namespace
parent
preceding
preceding-sibling
self

XPointer Node Tests

* Any Element
node() Any Node
text() A text node
comment() A comment node
processing-instruction() A processing instruction
point() A point in a resource
range() A range in a resource

Creating Points

start-point()

For example:

<?xml version="1.0"?>
<BOOK>
    <P>chapter 1 - Intro</P>
    <P>chapter 2 - conclusion</P>
</BOOK>

points right before the character 'e'

xpointer(/BOOK/P[2]/text()/start-point()[position() = 5])

Creating Ranges

Create ranges with two points: a start point and an end point
Points in same document
Start point is not after end point

XPointer functions

"range-to" Function

For each location in the context, range-to returns a range

Example: Locates the range from the start point of the element with 
         ID "chap1" to the end point of the element with ID "chap2"
         xpointer(id("chap1")/range-to(id("chap2")))

"string-range" Function

Returns a location set with one range for every nonoverlapping match to the search string. The match operation is case-sensitive.

Examples:

  string-range(/,"John")
  string-range(/,"John")[2]
  string-range(//STUDENT[3]/NAME, "John")[3]
  string-range(//STUDENT[3]/NAME, "John",6,2)[3]