This example is a simple tree (XML) to typed graph transformation.
The challenges here include (1) going from implicit references (via naming conventions, IDs, etc. in the tree) to explicit links in the target model, and (2) inducing explicit types in the target model from the generic tree structure (labelled nodes with children).
As depicted in the diagram below, source models represent (build) processes expressed in a declarative language (similar to make or ANT) consisting of Tasks and their requirements (as invoked Tasks). As an additional language feature, Tasks are grouped into Modules (an XML files is a module), and Tasks from a different Module can only be invoked if the module has been imported.
Target models represent the exact same information but with explicit links and types for the concepts in the language (showing the graph structure and interconnectivity clearly).
Properties [optional section]
Variants [optional section]
References [optional section]
This example was used in the practical session (organized and held by Andy Schürr and his research group) of the Modelling Wizards summer school 2012 
Artefacts [optional section]
A virtual machine hosted on Share is available with a workspace containing both (Ecore) metamodels, the concrete example used above, and a TGG formalizing the consistency relation as a set of rules: