How are you all dealing with 'Tagging' Information Rich Items

[igoldsmid]

This summary question of this post is:
For a complex Information Base, what are some of the best ways to design its 'system' of Attributes, Attribute Categories, and Attribute Values - in order to most effectively describe (Tag) what each Item is about - and ultimately to be able to Search across the Info Base to find Items logically related by an arbitrarily complex intersection of their assigned Attributes and Values.

so, I wanted to start a discussion around how UR users are dealing with the 'Tagging/Key Wording' of complex Items - Information Rich Items that need to be Tagged with many Key Words (that in fact would likely need to be logically organized into Key-Word-Groups which in UR terminology that would probably mean multiple Attributes/ Attribute Categories - with multiple Values/Key Words) to effectively and fully answer the question; "what is this Item about altogether?....

And specifically, trying to find the most efficient/effective way of defining/designing a system of Attributes/Categories and their Values to achieve this.
(And not only that - as the Information base grows, this would provide the ability to perform a 'Tag/Key Word' Intersection Search across a URD file to find Items that are logically related to each other by a complex intersection of multiple Attributes and their Values.)

Starting with a simple hypothetical 'problem' of how best to design and assign multiple Attributes and their Values to an individual Item:

Suppose I have an information rich 50 page pdf document, and let's say it has ten 'dimensions' of what it is about (in UR speak; this may be ten Attributes in one or more Attribute Categories)...

The key thing I can't get my head around at the moment is:

How to design and assign an effective combination of Attributes/Attribute Categories and their Values. Here's an example:

In Life Sciences, Drug Discovery Research & Development, their are many, many scientific disciplines:
Discipline 1, Discipline 2 etc...

This would suggest creating an Attribute called "Scientific Discipline" - which would contain multiple Values...

and suppose my 50 page pdf contains references to seven different scientific disciplines.....?

And, what if this pdf contained nine other information dimensions (Attributes/Categories) where each of the nine Attributes would logically need to have multiple Values assigned....

Without getting even more verbose, I'll conclude for now by saying that I am having difficulty getting my head around how to design a system of Attributes, Attribute Categories, and working with such where it appears that needing to assign (to the info Item) multiple Values for any Attribute would be necessary rather than logically incorrect.

So Is there a way of designing a system of Attributes and Attribute Categories such that assigning only one Value from any Attribute (to an Item) is logically correct, or is assigning (to the Item), multiple Values for some Attributes typical, normal and effective?

This would no doubt be a trivial problem to a Professional Database designer, but I am not one....

So,in essence, I need a much better understanding of the meaning and practical use of the Tagging system of Attribute Categories, Attributes, and Attribute Values....

Isn't it amazing how the use of the apparently simple concept of Attributes can have such far reaching consequences!?

If you've got to here, thank you for your patience! - and I am sincerely looking forward to your discussion points...