New helper query interface method

[Ray Plante]

On Thu, 14 Apr 2005, Guy Rixon wrote:
> If we have the query that just returns the list of identifiers, and we have
> the query that returns the document for one identifier, then we wouldn't need
> a paging arrangement; the client could do the paging by calling down the
> documents one by one by identifier. This would be a lot simpler.

Simpler, yes, but definitely not as efficient as a resumption token.  If 
the problem is too many result records, then fetching each one-by-one will 
incur a big performance hit.  

Nevertheless, returning a list of identifiers from a search and resumption 
tokens are both good ideas.  

I'll note that resumption tokens may not be a perfect solution for the 
Yuji's problem unless the client is able to indicate the maximum number of 
records it will get back.  This also suggests that the server MUST support 
the resumption token mechansim.  In contrast to OAI, resumption tokens are 
optional and a choice of the serving registry (not the client).  

cheers,
Ray