The XML Path Language (XPath) is an XSL sub-language designed
to uniquely identify or address parts of a source XML document. An
XPath expression can be used to search through an XML document, and
extract information from the nodes (any part of the document, such
as an element or attribute) in it.
About this task
The XML Path Language (XPath) is an XSL sub-language designed
to uniquely identify or address parts of a source XML document. An
XPath expression can be used to search through an XML document, and
extract information from the nodes (any part of the document, such
as an element or attribute) in it.
For more information about
XPath, see the following resources:
To create an XPath expression using the XPath Expression
wizard, complete the following steps:
Procedure
- Launch the XPath Expression wizard using one of these methods:
- On any select or match attributes
in an XSL file, right-click the attribute and click XPath
Expression.
- From any of the XSL editor wizards in which you can specify
an XPath expression for a field value. In the appropriate wizard,
click the XPath button.
- Select an XML file to use to build your XPath expression.
- In the Source Tree page, select the node you want to be
your context node. The context node is the starting point
for your XPath expression; it can be the document root node or any
node contained in the root node.
- Right-click it, and click Set Context. It appears in the Evaluation Context field.
- The empty field below the Evaluation Context field
contains your XPath expression. You can create or modify
it by selecting the appropriate options from the Source Tree and Reference
pages in the XPath Expression wizard.
- The Source Tree page tree lists all the nodes (such as
attributes and elements) in your XML document. Select the node you
want to search for, right-click it, and click Add to Expression. The node will appear in the expression field. You can repeat
this process for all the nodes you want to add to the expression.
- Click the Reference tab. The
Reference page lets you specify functions, operators, and a location
path for your XPath expression.
- Expand Functions Reference. It contains the following options:
- Node set. Functions that apply
to node sets.
- String. Functions used for dealing
with strings.
- Boolean. Functions used for
Boolean mathematics.
- Number. Functions used to manipulate
numeric values.
- XSLT. XSLT functions used in
XPath expressions.
- User defined. Functions that
are defined by the user.
- Expand the Functions Reference option you want to
work with, then right-click it and click Add to Expression to
add it to your XPath Expression. For more information about
each option, you can select it, and information about it will appear
at the bottom of the Reference page in the Details pane. You can also
refer to the related reference files.
- Expand Syntax Reference . It
contains the following options:
- Axis specifiers. Determines
the direction you move within the XML document.
- Node tests. Specifies what kinds
of nodes to search for.
- Operators . Contains the following
options:
- Node Set. Operators that combine or define
paths.
- Boolean. Operators that compare string
or numeric expressions, or Boolean values.
- Number. Operators that can be used to manipulate
numeric values.
- Expand the Syntax Reference option you want to work
with, then right-click it and click Add to Expression to
add it to your XPath Expression. For more information about
each option, you can select it, and information about it will appear
at the bottom of the Reference page in the Details pane. You can also
refer to the related reference files.
- You can also edit your expression manually in the expression
field. Content assist is available and can be invoked by clicking Ctrl
+ Space. Double-click the option you want to add to your
XPath expression.
- You can set the processor that is used to evaluate your
XPath expression. In the XPath Expression Builder on the right-hand
side at the top of the Results Tree pane, click the drop-down menu
icon and select on of the following options:
- IBM Processor for XPath 1.0
- IBM Processor for XPath 2.0
- Your XPath expression is automatically evaluated as you
create it. The results of it appear in node format in the Results
Tree pane. Click the Result Source tab if you
want to see your results in source code format. If you
do not want your XPath expression automatically evaluated as you type
it, you can change this option in the XPath expression builder preference
page. Click the XPath builder preference page button
to
access it.
- Click OK when you have finished
your XPath expression.
Results
If you launched the XPath Expression wizard using the XSL
editor, your XPath expression appears in your XSL file after you click OK.
If you launched it from an XSL editor wizard, it will appear in the
field you created it for.