1. A computer-implemented method of assigning a score to an ordering of a target language dependency structure given a source language dependency structure and an alignment between nodes in the source language dependency structure and nodes in the target language dependency structure, the method comprising: receiving a source language dependency structure indicative of a source language text fragment and a target language dependency structure; assigning a score to the order of dependent nodes, depending directly from a parent node, in the target language dependency structure; and wherein the target language dependency structure comprises a target language dependency tree and the source language dependency structure has nodes aligned with nodes in the target language dependency tree, and wherein assigning a score comprises: computing a metric indicative of a probability that a selected node in the target language dependency tree has changed from one of a pre or post modifier of its parent node to become another of the pre or post modifier of its parent node in the target language dependency tree given that a node in the source language dependency structure aligned to the selected node in the target language dependency tree was a pre or post modifier of its parent node in the source language dependency structure; and providing an output to a component of a machine translation system based on the assigned score.