What are obligate category?

What are obligate category? How these are different from intermediate categories. List out some intermediate categories.

The taxonomic categories, which are always used in hierarchial classification of organisms are called obligate categories.
The taxonomic categories from species to kingdom are broad categories or obligate categories. However, taxonomists have developed sub-categories in this hierarchy to facilitate more sound and scientific placement of various taxa.
Intermediate categories are sub-phyla, sub-classes, sub-orders, sub-families, sub-genera, varieties or sub-species.