XML Chapter 5: XPointers

XPointers

XPointer is a notation for pointing to specific elements within a document.
- Used as fragment identifiers for URI references.
- Like the #name part of an HTML link, but more powerful.
Example: point to the second chapter element in a document:
Since there are currently no implementations of XPointer, we will cover only the main features of the language.
XPointer allows you to use XPath notation to specify fragment identifiers. We have already seen some of XPath's capabilities in the Pattern Matching section of the chapter on XSL.

Here are some of the constructs you can use:

/ Child nodes. Example:
myfile.xml#xpointer(catalog/book)
Matches all book child elements within the catalog element.
// Descendant nodes. Example:
myfile.xml#xpointer(catalog//last)
Matches all last elements anywhere within the catalog element.
| Used to specify multiple nodes. Example:
myfile.xml#xpointer(//first|//last)
Matches all first and last elements anywhere in the document.
* Wildcard. Example:
myfile.xml#xpointer(//chapter/*)
Matches all child elements of chapter elements anywhere in the document.
@ Attributes. Example:
myfile.xml#xpointer(//book/@used)
Matches the used attribute of the all book elements in the document.
[ ] Tests. Example:
myfile.xml#xpointer(//book[@used="YES"])
Matches all book elements with a used attribute equal to YES.
[n] Position. Example:
myfile.xml#xpointer(//book[3])
Matches the third book element in the document.

Other constructs:

id() Identifies nodes with a particular id. Example: myfile.xml#xpointer(id("Tagore1"))
Matches the element with an id attribute equal to Tagore1.
descendant() Like //
ancestor() Identifies ancestor nodes. Example:
myfile.xml#xpointer(ancestor(id("Tagore")))
Matches the element that contains the element with an id attribute equal to Tagore.
preceding() Identifies preceding nodes.
following() Identifies nodes that appear after the current node.
preceding-sibling() Identifies sibling nodes that appear before the current node.
following-sibling() Identifies sibling nodes that appear after the current node.

XPointer extends XPath's capabilities: you can specify ranges in addition to single nodes.

This example matches the part of the document between the elements with id attributes equal to Tagore1 and Tagore2.

/	Child nodes. Example: `myfile.xml#xpointer(catalog/book)` Matches all `book` child elements within the `catalog` element.
//	Descendant nodes. Example: `myfile.xml#xpointer(catalog//last)` Matches all `last` elements anywhere within the `catalog` element.
\|	Used to specify multiple nodes. Example: `myfile.xml#xpointer(//first\|//last)` Matches all `first` and `last` elements anywhere in the document.
*	Wildcard. Example: `myfile.xml#xpointer(//chapter/*)` Matches all child elements of `chapter` elements anywhere in the document.
@	Attributes. Example: `myfile.xml#xpointer(//book/@used)` Matches the `used` attribute of the all `book` elements in the document.
[ ]	Tests. Example: `myfile.xml#xpointer(//book[@used="YES"])` Matches all `book` elements with a `used` attribute equal to `YES`.
[n]	Position. Example: `myfile.xml#xpointer(//book[3])` Matches the third `book` element in the document.

id()	Identifies nodes with a particular id. Example: `myfile.xml#xpointer(id("Tagore1"))` Matches the element with an `id` attribute equal to `Tagore1`.
descendant()	Like `//`
ancestor()	Identifies ancestor nodes. Example: `myfile.xml#xpointer(ancestor(id("Tagore")))` Matches the element that contains the element with an `id` attribute equal to `Tagore`.
preceding()	Identifies preceding nodes.
following()	Identifies nodes that appear after the current node.
preceding-sibling()	Identifies sibling nodes that appear before the current node.
following-sibling()	Identifies sibling nodes that appear after the current node.

XPointers

Lab 5D