 A corpus annotated with tree structure is known as a treebank. Clearly, such a corpus is not a raw record of attested utterances at all; it is a combination of a collection of attested utterances together with a systematic attempt at analysing their structure. Whether the analysis is added manually or semi-automatically, it is ultimately based on native speaker judgments. (Treebanks are often developed by graduate student annotators tutored by computational linguists; naturally, consistency between annotators is an issue that needs regular attention. See Artstein and Poesio, 2008, for discussion of the methodological issues.).