There is a definition of documentary attributed to John Grierson that I like:
“Documentary is the creative treatment of actuality.”
While cetainly not an end-all-be-all, I think it is a reasonable starting point.
I don’t have as good of a historical definition of Journalism. I did look it up on Wikipedi, which seems as good a place to start as any:
Journalism is a discipline of gathering, writing and reporting news, and more broadly it includes the process of editing and presenting the news articles. Journalism applies to various media, including newspapers, magazines, radio, and television. . . . [Read the entire entry]
Anyway, I’m not entirely sure where I am going with this, but I left in all of the additional Wikipedia links because the except is so inter-contextually dependant, it is almost not even a definition . . .
In this ongoing discussion, sometimes people substitute in “news” for “journalism.” To me, this is odd because I think the answer to the question, “Is Documentary Journalism?” is “Sometimes.” However, if the question becomes “Is Documentary News?” I think the answer should be “Almost Never.”