data model question - time fields

while working on the editorial guidelines, a question about the different fields "registering" time creation of items in the data model came up:

• thanks to lastInfoUpdate, the system creates and updates the time at which an item was created and modified
• for Digital Objects, we also have dateLastUpdated and dateCreated, what is the difference? To what is this supposed to refer to?
• there is also property source-last-update, what is this supposed to refer to? last ingest of the source where an item comes from? last update of the item at the source?
• there is a timestamp property coming from the DBLP ingest
• there is a year property

Could we clarify the purpose of these different fields (and merge some of them if needed)?