For my work on the huge pages patch for PostgreSQL I also had to write some documentation. This was the first time I did this, and so I didn't have a working documentation building environment. At first the PostgreSQL documentation seems fairly easy: install requirements, go to directory, type
sudo emerge -av app-text/openjade app-text/docbook-sgml-dtd app-text/docbook-dsssl-stylesheets app-text/docbook-xsl-stylesheets libxslt cd /home/ckruse/dev/postgresql/src/doc make
But since Gentoo handles installation of different versions of packages, it wasn't that easy. I always got this error message:
openjade:postgres.sgml:3:55:W: cannot generate system identifier for public text "-//OASIS//DTD DocBook V4.2//EN"
After reading some source code I finally got the solution: you need the 4.2 slot of the docbook SGML DTD:
emerge app-text/docbook-sgml-dtd:4.2 cd /home/ckruse/dev/postgresql/src/doc make
After that everything just compiles well.