Reference
The reference contains everything you look up: the commands of the layout file, XPath and functions, the command line options, the configuration as well as the glossary and the appendix. If you want to learn the Publisher from the ground up, start with the manual.
Commands
All commands of the layout file, arranged by topic
XPath & Functions
XPath expressions, layout and standard functions
Command line
All sp options in detail
Configuration
Configuration file and environment variables
Glossary
Terms and definitions
Appendix
Defaults, file names, internal variables