Despite the KTR extension, PDI transformations are just XML files. As such, you are able to explore them inside and recognize different XML elements. Look the following sample text:

<?xml version="1.0" encoding="UTF-8"?>
<transformation>
  <info>
    <name>hello_world</name>
    <description>My first transformation</description>
    <extended_description>PDI Beginner&apos;s Guide (2nd edition)Chapter 1</extended_description>
...
</transformation>

This is an extract from the hello_world.ktr file. Here you can see the root element named transformation and some inner elements, for example, info and name.

Note that if you copy a step by selecting it in the Spoon work area and press Ctrl + C, and then paste it to a text editor, you can see its XML definition. If you copy it back to the canvas, a new identical step will be added to your transformation.

XPath is a set of rules used for getting information from an XML document. In XPath, XML documents are treated as trees of nodes. There are several kinds of nodes: elements, attributes, and texts are some of them. As an example, world, country, and isofficial are some of the nodes in the sample file.

Among the nodes, there are relationships. A node has a parent, zero or more children, siblings, ancestors, and descendants depending on where the other nodes are in the hierarchy.

In the sample countries file, country is the parent of the elements name, capital and language. These three elements are children of country.

To select a node in an XML document you have to use a path expression relative to a current node.

The following table has some examples of path expressions you may use to specify fields. The examples assume that the current node is language:

For more information on XPath, visit the link http://www.w3schools.com/XPath/.

In order to specify the name and location of an XML file you have to fill in the File tab just as you do in any file input step. What is different here is how you get the data.

The first thing you have to do is select the path that will identify the current node. This is optimally the repeating node in the file. You select the path by filling in the Loop XPath textbox in the Content tab. You can type it by hand, or you can select it from the list of available paths by clicking on the Get XPath nodes button.

Once you select a path, PDI will generate one row of data for every found path.

In the Time for action – getting data from an XML file with information about countries section, you selected /world/country/language. Then PDI generates one row for each /world/country/language element in the file.

After selecting the loop XPath, you have to specify the fields to get. In order to do that, you have to fill in the grid in the Fields tab by using XPath notation, as explained previously.

Note that if you press the Get fields button, PDI will fill the grid with the child nodes of the current node. If you want to get some other node, you have to type its XPath by hand.

Also note the notation for the attributes. To get an attribute you can use the @ notation as explained, or you can simply type the name of the attribute without @ and select Attribute under the Element column, as you did in this section.

Any time you see a red dollar sign by the side of a textbox, you may use a variable. Inside the textbox you can mix variable names with static text, as you did in Time for action – getting data from an XML file with information about countries section when you put the name of the destination as ${LABSOUTPUT}/countries_info.

To see all the available variables, you have to position the cursor in the textbox, press Ctrl + Space , and a full list is displayed so you can select the variable of your choice. If you place the mouse cursor over any of the variables for a second, the actual value of the variable will be shown.

If you know the name of the variable, you don't need to select it from the list. You may type its name, by using any of these notations: ${<name>} or %%<name>%%.