In some kind of parsing activity (in our case, a crawler) one is often interested to know the attributes of a small subset of element types. The other attributes generate a large amount of garbage (strings, CharBuffers, etc.) that must be collected.
It would be nice to be able to "register" with a parser a set of element types, and then only attributes associated with such element types would be parsed and put into an AttributeList. For the other element types, an empty list (possibly a singleton) could be returned.