Note that meta data from single items (corpora or documents) is
preserved during concatenation and intelligently merged into the newly
created corpus. Although we use a sophisticated merging strategy
(by using a binary tree for corpus specific meta data and by joining document
level specific meta data in data frames) you should check the newly
created meta data for consistency when merging corpora with (partly)
identical meta data. However, in most cases the meta data merging
strategy will produce perfectly combined and arranged meta data
structures.