[OPEN-ILS-GENERAL] Importing holdings data

[Jason Etheridge]

> Another question.  Why a record id and a tcn?  I'm probably missing something rather obvious here.

This came from the first users of Evergreen, where legacy TCN's were
given much importance, since useful information (such as record
origin/quality) was embedded into them, and the whole 001/003/035
manipulations that MARC 21 describes wasn't reliable in their previous
ILS, and probably was overlooked or not a priority at the time when
Evergreen was first developed.  They're also used as a poor man's way
of preventing duplicate imports in the Z39.50 interface.

I think we mostly know better these days.  Opaque id's good.
Embedding meta-data everywhere bad.  There's an Evergreen setting now
that can make the TCN equal the record id automatically.

> fingerprint: Eh?  So how would I generate this?

There should be a trigger to handle this for you (maybe depending on
your version of EG).  It's used for grouping records with similar
titles into metarecords (think FRBR-ish, but for lumping different
formats and editions together).  See the metabib.metarecord table.

> last_xact_id: A fresh db has one entry in the table with "FOO" in this field.

This is used for optimistic locking of the record.  Two catalogers try
to update a MARC record at the same time, the one with the right
last_xact_id wins.

> asset.copy also has a few murky fields.
>
> id, call_number, copy_number?  How do these numbers relate?

Id on any table is a unique opaque id used internally within Evergreen
to identify a specific row in the table.

Call number is indeed a reference/foreign key to the asset.call_number
table.  The label field in the call number table is typically what's
printed on the spine of a book (a Dewey decimal or library of congress
identifier).

Copy number is completely optional.  Books have barcodes and call
numbers, but some libraries find it useful for them to also have
low-value ordinal numbers (#1, #2, etc., perhaps printed on the spine
label, or even penciled in inside the book cover) for quick/easy
differentiation of identical copies.

> dummy_title and dummy_author are a mystery.

Used to temporarily hold title and author information for
"pre-cataloged" items created in the Check Out interface, where the
item doesn't have a true bib record associated with it yet.  Such
items will always have a magic value of -1 in asset.copy.call_number.
There is an actual asset.call_number with an id of -1, pointing to a
biblio.record_entry with an id of -1, but that placeholder record will
never show up in a bib search in the public catalog.

A pre-cataloged item can be transferred to real bib/call number later
and retain its circulation history.

-- 
Jason Etheridge
 | VP, Tactical Development
 | Equinox Software, Inc. / Your Library's Guide to Open Source
 | phone:  1-877-OPEN-ILS (673-6457)
 | email:  jason at esilibrary.com
 | web:  http://www.esilibrary.com