To create e.g. the PDF output where the contents of the XML file are displayed, you need to connect the nodes of the XML tree with elements on your sheet used as placeholders. This action is called Grouping. Grouping the page or elements to certain nodes of the XML tree establishes a connection to specify the path through the tree file to the one node containing the data, which you want to see, displayed in the element. As the application reads the XML tree always from the top, this must be considered in the path to the correct node. There are some factors that influence the path to the correct node.
An example: a new layout page is grouped to the top node of the XML file, in our example it is Report. Every element connected to XML contents, which is placed on the sheet, now shows the path to the node without Report, e.g. ProductGroup/Name.
If the page is grouped e.g. to the node Report/ProductGroup/Product, the elements on the sheet now already refer to those nodes contained in Product and show only the name of the node because the first part of the path is already determined by the page grouping:
And if an element like a table is itself grouped to a node (in this example it is grouped to Report/ProductGroup/Product/Properties), the elements placed into the table will only show the name of the node because the first part of the path is already determined:
Of course it is also possible to place nodes from all levels of the XML file on the sheet or in tables, XSLfast will automatically add the necessary elements for the right path. This example is supposed to give you a general idea what grouping is and what it is used for.