The readme.txt under /local, related to local plug-ins/modifications, appears to contain incorrect information. The specific excerpt I came across that made me suspicious is the following:

Standard plugin features:

• /local/xxx/db/version.php - version of script (must be incremented after changes)
• /local/xxx/db/install.xml - executed during install (new version.php found)
• /local/xxx/db/install.php - executed right after install.xml
• /local/xxx/db/uninstall.php - executed during uninstallation
• /local/xxx/db/upgrade.php - executed after version.php change
• /local/xxx/db/access.php - definition of capabilities
• /local/xxx/db/events.php - event handlers and subscripts
• /local/xxx/db/messages.php - messaging registration
• /local/xxx/db/external.php - web services and external functions descriptions
• /local/xxx/lang/en/local_pluginname.php - language file

I believe version.php should be under /local/xxx/, and not under /local/xxx/. Further in the document, /local/xxx/version.php is explicitly mentioned in another exampe.

I believe external.php is supposed to be services.php, and a second file, externallib.php, should be under /local/xxx/, and not in /local/xxx/db/

These changes would make it in compliance with the standards used in other plug-in types I've worked with so far in Moodle 2.0. I have not actually gotten deep into working with the local plug-in type yet, so I will see if my changes actually even work first.