I'm in a process of acquiring a corpus of documents on educational courses.
For example there is an educational course called "OOP" and it can have documents from 2008, 2009, ... 2016 etc.
And there are a lot of these courses, each one with programs from different years (hopefully)
So 1 document is 1 programm of one course for one year.
I want to calculate how much does a course changes per year.