How to model 'subjects'

In scope: 
See : http://www.cs.vassar.edu/faculty/welty/papers/subjects/subject.html. 
This paper describes 4 alternative models, which are compliant with the CRM methodology.

IFLA FRBR, Subject Relationships:

The "has as subject" relationship indicates that any of the entities in the model, including work itself, may be the subject of a work. Stated in slightly different terms, the relationship indicates that a work may be about a concept, an object, an event, or place; it may be about a person or corporate body; it may be about an expression, a manifestation, or an item; it may be about another work. The logical connection between a work and a related subject entity serves as the basis both for identifying the subject of an individual work and for ensuring that all works relevant to a given subject are linked to that subject.

Patrick LeBoeuf distinguishes:

The analysis (and indexing) of fine arts museum objects might result into 2 kinds of relationships:
1) "ofness" relationships vs. "aboutness" relationships
2) Erwin Panofsky's categorizations: "pre-iconographic" indexing 
"iconographic" indexing / "iconologic" indexing.

As I tried to explain in my paper, librarians have constantly mistaken "object" relationships for "subject" relationships; as long as they only dealt with books, it was not very problematic, but from the moment they strove to catalog still pictures and objects the same way, the whole thing became an indescribable mess... I think librarians shouldn't pass on this mess to the CRM community!"

Proposal, Monterey Feb. 2002:

The CIDOC CRM should model only the aboutness relationship.

Should be covered by decision on P67 refers to, issue 86