Handling of ISBD cataloging without punctuation (LDR/18=c)

Updated as of February 21, 2020

Overview

We addressed these fields only at this time:

we did not account for multiple subfield a's because that means there will likely be a,b,a,b… in which case we recommend that cataloger NOT use LDR/18=c

did not account for multiple subfield instances, same recommendation as above, e.g. if you have something like this, a cataloger should not use LDR/18=c:
- 300 ##$a 1 score (30 pages) ; $c 20 cm + $a 16 parts ; $c 32 cm
also, in order to create punctuation between subfields, I had to also enforce an order. I wrote the rules to anticipate subfields in this order: 3 a f b c e g. If there are complex combinations of a+f, a+f+g in a single 300, that may be another case where staff should manually punctuate and not use LDR/18 =c

502
Did not include 505 because of the levels of variation that can be found with different material types, e.g. in music, $r is not always preceded by a slash (for performers), and a $t is sometimes preceded by a period or a semicolon (for hierarchical titles) – and a $g can be lots of things.

For existing 264 rules, add condition that LDR/18 not equal c
When LDR/18 = c, we use multiple PNX fields to make sure the display label is correct, since it changes based on indicator values
Field 264 is also likely to exist with just a subfield c so we accounted for that as well.