Ok, so I guess your point I can summarize like this:

MD arrays shouldn't need special treatment. We should be able to compose what we need from lower levels that have only a small number of primitives. Rich functionality must be able to be built up from this. If we can't so this, that is, if the bottom level has to have lots of elaborate constructs, then something is wrong with the composition model.

yes... if the goal is to provide a fine-grained XML-model as in your example. If there's a need to expose an MD array as a single XML element, then we need a new datatype. Otherwise I think treating MD arrays as special starts mixing types and reader params in ways that limit composition. Jim