Practical Implementation of the UDC

	UDC can be used at many different levels of detail
		e.g. broad groupings with a high level of generality, or highly detailed indexing of complex technical information.
		in the former case, high-level (i.e. short) class marks would be selected, and in the latter, the lowest level of detail (i.e. the longest class marks).
		some systems use a combination of methods, indexing in great detail but shortening the class marks for shelving purposes.
	Some of the decisions that need to be made to decide at what level items should be classified are as follows:
		What is the purpose of classifying? The physical arrangement of items (shelf order); indexing of information contained in them; or both?
		How many items are there, and how much and how fast is the system likely to grow?
		What use will be made of the collection (what kind of information will you want to extract from it?)
		What other characteristics do you need to take account of?
			What other characteristics do you need to take account of?

Generally, the degree of detail needed is influenced not just by the size of a collection but also by how varied it is.