XPath¶

XPath is a method for traversing elements and attributes (nodes) in a XML document. In CrossGenerate this is used in the configuration files to point to model and XML template nodes.

Basics¶

For the basic explanation on XPath, please consult the following website:

W3Schools - XPath Tutorial

Examples¶

Here some examples are given which represent commonly occuring configurations containg XPath when using CrossGenerate.

Selection¶

When using XPath an important concept is the use of axes. An axis is a relationship of a certain node or set of nodes in the XML document to the current node. When traversing nodes the first part of the XPath is usually the axis. If no axis is given, the current node (self) is the default. See W3Schools - XPath Axes for an explanation of this concept.

Child node selection¶

The '/' at the beginning of the expression makes sure it selects all attribute elements relative to the current node.

/attribute

Child attribute selection¶

In this example we want to select all name attributes of the current node. This will result in a single result or no result, since a node can have only one attribute with a certain name.

/@name

Parent attribute value¶

To get to a node of the parent use the '../' axis. For example here we select the name attribute of the parent.

../@name

Any attribute selection¶

The '//' at the beginning of the expression makes sure it selects all attribute elements no matter where they reside in the XML document (so not only descedants of the current node).

//attribute

Filtering¶

Filter on a element¶

In this example we want to select the attributes where the datatype is 'varchar'.

/attribute[@datatype='varchar']

Case insenstive filter¶

To make the comparison in the filter case insensitive, make sure to use lower-case() or upper-case() functions before comparing the value.

/attribute[lower-case(@datatype)='varchar']

One can also use different boolean type functions to perform checks in filters. For example contains(), starts-with() & ends-with().

Filter on attribute¶

Here we add a filter on the current datatype attribute. See how we use the '.' to select the current node value.

/attribute/@datatype[.='varchar']

Functions¶

There are quite some functions available in XPath to perform different types of actions. For example string manipulation or mathematical functions. See the references on the bottom of this page for an overview of all functions available.

Concatenate¶

Here we use the concat function to concatenate the current node name attribute and the parent node name attribute.

concat(.@name, ' - ', ../@name)

Count¶

Here we use the count function to count the numbers of attributes.

count(/attribute)

References¶

In this section a list of relevant references is given.