In librarian parlance entities, whether books or journal articles or whatever, can be said to have an “aboutness.” And as a cataloger its my job to describe that aboutness with subject headings. I’m working in an archives setting now and my job, essentially, is to sit down with photos such as the one below and, following strict rules, create a digital record that will help researchers find it in the future.
Because we place a premium on organization and arrangement only authorized subject headings are permitted, something called a “controlled vocabulary.” In the work I’m doing now our controlled vocabulary comes from the Library of Congress. One of the defining characteristics of the LoC subject headings is that they are hierarchical, broad terms are subdivided into narrower terms, which are further divided and modified in rather rigid ways.
So those are the basic rules of the game. The objective is to describe the item so that others will find it, but within the constraints set out by the LoC (typically there are in-house rules you have to take in to consideration too, etc). Alright, given all that: What is this picture about?