to user, related information given togethor, but is really stored in most efficient means possible, best balance of factors such as access time (search, sort, etc), modification time (change data and append), new item time, storage space, number of accesses to storage media.
all instances of data in any format should be able to be looked at from ‘finder’ level and relatable
redundant and inconsistant data can be eliminated using spare cpu time during idle time
relatable in hierarchial type view, getting more specifically related as go deeper in hierarchy, very generally related near top.
search time reduced using hierarchy by eliminating items in unrelated branches: searching for a friend named Amy would search through a friends subdir before/instead of business partner dir.