This is the kind of information that's being referred to as "administrative data" in OCLC's new Registry framework (an SRU application, btw). The client can request an "adminData" object in addition to requesting the object itself.
You can see the Registry framework in action here:
who suddenly has the very grand title:
Consulting Sotware Engineer
> -----Original Message-----
> From: SRU (Search and Retrieve Via URL) Implementors [mailto:[log in to unmask]]
> On Behalf Of Ray Denenberg
> Sent: Thursday, May 03, 2007 12:37 PM
> To: [log in to unmask]
> Subject: Re: Record Metadata Schema (was Re: "collection" context set)
> From: "Ed Summers" <[log in to unmask]>
> > Can someone briefly describe the use case for
> > x-info-99-metadata?
> It's to be able to get record metadata - metadata about a retrieved record
> (as contrasted with metadata about the resource that the record describes,
> which is already in the record, assuming that you're retrieving metadata
> records to begin with).
> For example, language - the language of the record (not the language of
> resource described by the record), its rank within the result set, who may
> modify the record, when the record was created, last updated, who created
> it, who modified it, etc.