2011/1/27 Jonathan Rochkind <[log in to unmask]>:
> "If the best you can do is an external Handle/PURL set-up, then it is better than nothing."
>
> I would say that it's SOMETIMES better than nothing. It depends on what you're doing, what your requirements and goals are. Not every application needs long-term persistence of URLs -- whether through an 'abstraction layer' or not. ('abstraction layer' is just an implementation detail to get long-term persistence of URLs accross systems changes, right?  You don't always need something called an 'abstraction layer' to do that).  Almost every application does need bookmarkable URLs for the short/medium-term though.  If you're sacrificing short-term bookmarkable URLs for long-term-goal persistent but confusing/non-transparent/not-discoverable URLs, that may or may not be a good trade off.

I *think* this may be pertinent, but it may also be a tangent.

For the DLG[1] and CRDL[2], we make use of what for
lack of a better term I refer to as the DLG handle service.

It's internal to our shop, but external to the collections it
serves, and is my attempt to be able to provide bookmarks
to items that may have been retrieved via non-bookmarkable
urls.

Both DLG and CRDL are aggregators of both local and
state-wide/nation-wide collections.  So the handle service
maintains a concept of "repository" (the owner of the collection),
"collection", and "item".  Each of these has an ID, e.g., the
ID for the repo "Digital Library of Georgia" is 'dlg', for the coll
"Vanishing Georgia" is 'vang', for the item "Photograph of Lillian
Carter, Plains, Sumter County, Georgia, 1976" is 'sum150'.

The item's bookmark then (with some handwaving about the
repo id) is:
    http://dlg.galileo.usg.edu/vang/id:sum150

Other examples:

A "persistent url" for a query in DLG:
    http://dlg.galileo.usg.edu/query:bush

Item records *in the aggregator database* of DLG:
    http://dlg.galileo.usg.edu/id:dlg_bald_am-451
    http://dlg.galileo.usg.edu/id:dlg_vang_sum150

Item records in the collections' sites:
    http://dlg.galileo.usg.edu/bald/id:am-451
    http://dlg.galileo.usg.edu/vang/id:sum150

And similar examples from CRDL:
    http://crdl.usg.edu/query:bush

    http://crdl.usg.edu/id:lbj_timeline
    http://crdl.usg.edu/id:dlg_bald_am-1259
    http://crdl.usg.edu/id:wsu_wsuboh_jacktanner

To get to the point, when we display an item (in the
interfaces that we control ourselves) we include in
the item display a "Bookmark" url that is one of these
handles.  For example, the actual url for the last item
above looks something like this:

http://crdl.usg.edu/cgi/crdl?action=retrieve;rset=001;recno=4

That's clearly not bookmarkable outside of the existing
browser session, so in the item display, we have this
line:

Bookmark: http://crdl.usg.edu/id:wsu_wsuboh_jacktanner

In that line, the URL *is* clickable.

I realize that this handle strategy flies in the face of
"opacity", since the handle contains indicators of
ownership.  I guess I'm just not in that camp, at least
not for these collections.

Again, I'm not sure the above is really a useful response
to the original query, but it came to mind, so I thought
I'd toss it in.

Regards,

Brad

[1] http://dlg.galileo.usg.edu/
[2] http://crdl.usg.edu/