We started from an initial corpus that did not have revisions, and kept adding new documents and revising existing documents. The revision operations we used were deletion, addition and replacement of words, sentences, paragraphs, section names and document titles. The addition of words, ..., section names, and new documents were pulled from the Wikipedia abstracts. We generated six data sets using different random seeds, and each data set contained six corpora (Corpus 0 - 5). 
 Question: What are simulated datasets collected?
There are 6 simulated datasets collected which is initialised with a corpus of size 550 and simulated by generating new documents from Wikipedia extracts and replacing existing documents