The main problem I see with transparent structures is that they are also inherently mutable. Some of the operation provided may well make use of that - for example removing whitespace. And, internally, it may be that the structures are created and then filled - as opposed to building the substructures and then creating the structure. I really haven't looked. But, in a larger sense, it is what it is. The API provides transparent structures and there may be code that relies on it. I may even rely on it somewhere. So, leaving then as transparent is probably the best way to go - with prop:custom-write properties to limit the resulting print consequence. Rewriting it could always be Neil T's next project. :) Doug <div class="gmail_quote">On Mon, Oct 3, 2011 at 4:06 PM, John Clements <<a href="mailto:clements@brinckerhoff.org">clements@brinckerhoff.org</a>> wrote: <blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;"><div class="im"> On Oct 3, 2011, at 3:01 PM, Doug Williams wrote: > The fact that transparent structures also print all of their element - in this case recursively, ad nauseam - is more of a side effect. In that case, I think prop:custom-write properties should be added. I assume any of the print limiting options in my case still walk the entire structure and create a several tens of megabytes long string just to truncate it. </div>I see. I misread your first mail as suggesting that the XML structures should not be #:transparent. John </blockquote></div>