I was amused to read:
At a high-level, CXML can be thought of as a set of property/value pairings. Facets are like property values on an item, and facet categories are groups of facets. For example: if a collection had a facet category called “U.S. State,” then “Georgia” could be a facet in that category. Depending on authoring choices, these facets may be displayed as filters in the PivotViewer collection experience, or included in the details of an item. Collection XML Schema
Sounds a lot like the Topic Maps Reference Model.
Or, the game of twenty questions.
That is the subject you are identifying is broader or narrower depending upon the number of key/value pairs you specify.
The Pivotviewer allows you to go from a very broad subject to a very narrow, even a specific one by, adding on key/value pairs.
Legends enable users to arrive at the same broad or narrow subject, even if they have different key/value pairs for that subject.
Hey, that is rather neat and practical isn’t it? (Take note Lars. He knows which one.)
Will have to investigate how to combine collection XML schemas to make that point.
More to follow on this topic (sorry) anon.