Hello all,
After trying very hard to convince myself otherwise, it is yet my belief that
Evergreen needs to augment its current item organization hierarchy with an
additional layer for proper volume (part) support. My only intention in
writing this email is to hopefully spur a larger discussion on this matter.
For the purpose of this discussion, I will define volume as "a portion of a
bibliographic whole."
As it stands, the asset.call_number table is being overloaded to function as
both a place to hold the call number and a place to hold volume information.
Under non-volume circumstances, the call number (and subsequently its attached
copy-items*) are representative of the bibliographic whole, and everything is
simple, predictable, and working. However, when one introduces volume
information into the call number field, two problems result.
First, it becomes difficult (computationally) to group together the
bibliographic wholes. For instance, consider a minority case of three copies*
of John Calvin's Institutes, often sold in a multi-volume set. It is not
uncommon for our library to have the same exact bibliographic entity in
multiple collections serving different user needs. Currently in Evergreen we
might end up with something like:
Title: Institutes
Call Number 1: CN123.A123 V.1
Call Number 2: CN123.A123 V.2
Call Number 3: P345.A345 V.1
Call Number 4: P345.A345 V.2
Call Number 5: J789.A789 V.1
Call Number 6: J789.A789 V.2
This sort of setup is generally still useable, but what if we want to determine
the seemingly simple question of "How many copies* of this title do we have?"?
We cannot easily answer it, as the computer does not understand the implied
relationship between call numbers which are only related by being mostly the
same. We also need to be very careful when doing simple operations such as
changing a call number or discarding a copy*, as we need to do the same action
multiple times.
A more complete setup would simply add a new layer to clarify things:
Title: Institutes
Call Number 1:CN123.A123
Part: V.1
Part: V.2
Call Number 2:P345.A345
Part: V.1
Part: V.2
...
I am using the word "Part" here to imply that this layer would be useful for
other titles which have multiple parts that are not necessary volumes.
The second volume-related problem involves any operation which may be specific
to a certain volume, such as holds. If all items from the above example are
checked out, but I need V.1, what do I place a hold on? To address this
concern, we would need to add some sort of "meta-volume" table. Where call
numbers now expressly represent a grouping of a bibliographic whole,
"meta-volumes" are a separate but complementary grouping of like parts:
Title: Institutes
Meta-volume 1:
Part: V.1 (CN123.A123)
Part: V.1 (P345.A345)
Part: V.1 (J789.A789)
Meta-volume 2:
Part: V.2 (CN123.A123)
Part: V.2 (P345.A345)
Part: V.2 (J789.A789)
This concept is in most ways independent of the first, and could be dealt with
separately, but I am introducing it here because I am well aware that there are
many other ways to model all of these relationships, and recognizing this need
might inspire a better overall model. I have tried to focus my thoughts on a
minimal disruption to the current structure, but perhaps this discussion will
conclude that a larger overhaul is needed.
At this point, my primary concern is how best to deal with the 95% of cases
which do not need this additional layer. Ideally any changes made would
augment the current model in an unobtrusive way.
I hope that this message can inspire an interesting and fruitful dialog.
Sincerely,
Dan Wells
* (The term "copies" is also overloaded in this discussion, as it could mean
the physical manifestation of a single volume (part) or the entire whole, but I
will do my best to keep things clear by referring to rows in asset.copy as
"copy-items".)
