s2-publishing-domain

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:

1. Take the first 12 digits
2. Multiply each digit alternately by 1 and 3 (positions 0-11)
3. Sum all products
4. 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 000000 suffix 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)