A few comments on metadata, specifically on IEEE-derived metadata, that address a few points that have explicitly or implicitly been brought up in Quinn's paper and the ensuing discussion. Some of these may have already been made, in which case accept my apologies for repeating them.
Structured metadata is by nature extensible.
This is a major difference between IEEE style metadata and the Dublin Core approach, which came first. The rest of the metadata is meant to be a common denominator that handles the attributes of LO's most important for the most common general purposes. There is a common misconception that metadata tags will be included in learning resources themselves. In other words, instead of a Web page containing an extra set of metadata tags, a database will include a pointer to the Web page and one or more metadata records will have the URI of the Web page as their object. All these different views can be simultaneously supported by different metadata descriptions of the same resource.