BQS — issue: excluded attributes

The BQS has a notion of the "excluded attributes". They can be
specified in query methods and cause that the resulting collection has
some attributes missing. The intention was to allow to create more
lightweight collections (without long abstracts, for example). This reason
is still valid and I am not going to ask to remove it from the query
methods.
However, during our implementation we found that also other "user
pattern" is quite often: To create a collection, then ask for few
attributes (like titles), and then ask for the another few attributes, and
only that, finally, ask for the (whole) collection. The existence of
excluded attributes in query methods makes it possible to realize such
pattern - but the implementation become quite complex. Because whenever
the user wants to change the set of excluded attributes, the server has to
create a new collection (which may be optimalized, I know, but still it is
a hassle for the implementation).
Therefore, I am thinking about adding the "excluded attributes"
parameter also to the retrieval methods.
I would not expect big problems from the FTF's P&P point of view,
because I hope that I can prove that adding such parameter is not new
functionality but only a convenient way how to achieve already existing
functions. However, I would like to ask for your advice, if this addition
is or is not bad from the BQS architecture point of view. I know that our
implementation (and perhaps other implementations as well) would be much
cleaner with having these attributes, but is that enough to justify the
suggested change?

Resolution (would be):

To add a parameter "in AttributeList excluded" to the retrival methods
(all in BibRefCollection interface):

• retrieve_all_elements()
• create_iterator()
• find_by_id()

see below