A collection description is the formalization combined with the Pattern Expression, that documents the used patterns and the rationalizations upon which the collection is based.
So the abstraction layers are:
Pattern expression -- The general, and yet formalized, description of the process and thoughts that forms the basis of the collection architecture. With references to a series of connected patterns.
Collection description -- A short, more technical, description of the elements that form the collection.
Technical/Collection formalization -- The actual DOMS collection described. This should be represented in the best possible way, it can be a diagram, it can also be represented by a XML file, or parts thereof. Other descriptive measures should also be considered.
Pattern expression
The why
Write your pattern expression here, it's the rationale behind the collections structure.
Collection description
The What
Sum up the elements in the collection here
Workflow
The how
Describe the intended usage of and content addition to this collection, use all available measures that help clarify on the subject. Consider images in addition to text.
Technical
Be concrete and go into detail of things that require it, especially parts of the collection that is complex or of a special nature.
Consider using a drawing to illustrate relations or for instance include code/XML snippets