PROLEARN has released Harmonization of Metadata Standards.
Here's an excerpt from the "Introduction":
Today there is a plethora of metadata specifications (such as IEEE LOM, Dublin Core, METS, MODS, MPEG-7, etc.), many of which are useful in whole or part for activities related to teaching and learning. While each specification in itself is designed to increase system interoperability, we are increasingly seeing systems that need to work with more than one of these specifications. Adding support for an additional specification generally presents a significant amount of added complexity in implementation. The reason for this is a lack of harmonization between specifications. . . .
Existing solutions to the metadata harmonization issue are few—systems are either limited to a single specification, or implement ad-hoc solutions that only work in that particular environment. There are many examples of "mappings" between specifications that provide partial solutions to the problem, but generally fail due to low-fidelity translations and lack of generality (i.e. the mapping only works for limited parts of specifications). Another solution is to create a top-level data model that encompasses the common aspects of all the specifications. This has proven to be feasible in relatively well-constrained domains such as resource aggregation. . . In the field of general metadata, where there is no such common ground, such an approach is substantially less likely to be successful. . . .
The deliverable begins with a short introduction to metadata in Section 3. Section 4 discusses a set of metadata specifications that are highly relevant to learning and teaching. Section 5 forms the core of the deliverable and analyses the harmonization issues among a chosen set of specifications. Section 6 generalizes the analysis in Section 5 and makes a deeper analysis of the relationship between IEEE LOM and Dublin Core. Section 7, finally, points to possible ways to address the identified harmonization issues.