15. The system of claim 9 , wherein the processor is configured to cluster the obtained sets of annotations into annotation clusters based on the features within the piece of source data identified by the annotations.
15. The system of claim 9 , wherein the processor is configured to cluster the obtained sets of annotations into annotation clusters based on the features within the piece of source data identified by the annotations. 18. The system of claim 15 , wherein the data annotation application further configures the processor to: determine an error rate for each annotator based on the annotation clusters; and group the annotators into annotator groups based on the determined error rate for the annotators.