another common form of collaboration involves digital collections. a wir can provide training on digitization, and help upload media (with any existing metadata) to wikimedia commons. wikimedia volunteers can then translate, extend, and reverify metadata, categorizing media and manually transcribing and structure scanned documents on wikisource. the description and categorization functions on wikimedia commons are sometimes preferred to those of commercial websites and the institution's catalogue software. media added to commons are used in wikipedia, both by the wirs and by volunteer editors.