By name: s2-publishing-domain description: Book publishing domain knowledge including ISBN, BISAC codes, and industry pricing standards. user-invocable: false
S2 — Publishing Domain Knowledge
Background knowledge for the book publishing domain. This skill is loaded automatically by Claude when relevant — it is NOT available as a slash command.
ISBN-13 Validation (Full Algorithm)
ISBN-13 is a 13-digit identifier. The last digit is a check digit computed as:
- Take the first 12 digits
- Multiply each digit alternately by 1 and 3 (positions 0-11)
- Sum all products
- Check digit =
(10 - (sum % 10)) % 10
Example: ISBN 9780306406157
- Digits: 9,7,8,0,3,0,6,4,0,6,1,5,7
- Weights: 1,3,1,3,1,3,1,3,1,3,1,3
- Products: 9,21,8,0,3,0,6,12,0,18,1,15
- Sum: 93
- Check: (10 - (93 % 10)) % 10 = (10 - 3) % 10 = 7 ✓
Important: The regex-only validation in utils/validators.py is incomplete.
When asked to improve ISBN validation, implement the full check digit algorithm above.
Valid prefixes: 978 (most books) or 979 (overflow and some music).
BISAC Subject Codes
BISAC (Book Industry Standards and Advisory Committee) codes categorize books:
- Format: 3-letter category + 6-digit number (e.g.,
FIC000000) - Common prefixes:
FIC(Fiction),NON(Nonfiction),JUV(Juvenile),YAF(Young Adult Fiction),COM(Computers),SCI(Science) - The
000000suffix means "General" within that category
Pricing Conventions
- Always store prices in cents (integer) to avoid floating-point errors
- Display format:
$XX.99(US convention) - Common price points: $9.99, $14.99, $24.99, $29.99
- Ebooks typically 30-50% less than physical edition
Library of Congress Classification (Basics)
- Single letter = broad class (e.g., P = Language and Literature)
- Letter + subclass (e.g., PS = American Literature)
- Used for shelving in academic/research libraries
- Different from Dewey Decimal (used in public libraries)