Level of description ("granularity")
Is the resource part of a larger resource?
Does it contain other resources within it?
Analogy: Russian nesting dolls: one small doll nested inside of another larger doll, which is inside yet another, and so on, to multiple levels of larger and smaller dolls inside of one another
Which level of the multi-layered resource are you selecting for description / cataloging?
Keep your description consistent for the selected level (e.g., title, dates, URL)