Hi Barton
...and then sub-divisions of the thousands are done after the decimal point -- 001.1, 001.2, etc...
as such, I don't think that callnumber 1.1 is a valid DDC number... it lacks the class and hundred-level group, and should, for the purposes of cn_sort, be converted to 001_100000000000000.
(Numbers above are taken from https://www.oclc.org/content/dam/oclc/dewey/DDC%2023_Summaries.pdf).
Looking deeper into it it seems I was just talking about the classic "decimal classification" which doesn't have leading zeroes. There are too many variants of it, one of them being the Dewey Decimal Classification / DDC - which actually seems to behave as you say, including leading zeroes. I wasn't aware of that difference. As far as I know the DDC is mostly used in the USA but also in Europe many peopöle are referring to "Dewey" when they actually mean their local decimal classification. So I guess many libraries are filling the DDC fields with content that is actually not proper DDC but their own variant of a decimal classification (for example I would think in Europe it will often be another hairy variant of the Universal Decimal Classification / UDC that behaves the way I described - see https://en.wikipedia.org/wiki/Universal_Decimal_Classification). Best wishes: Michael -- Geschäftsführer · Diplombibliothekar BBS, Informatiker eidg. Fachausweis Admin Kuhn GmbH · Pappelstrasse 20 · 4123 Allschwil · Schweiz T 0041 (0)61 261 55 61 · E mik@adminkuhn.ch · W www.adminkuhn.ch