Why are some of my modules reporting missing inter-module dependencies after migration? I'm troubleshooting modules after a host migration--did I miss something? Before I changed my host I backed up MySQL database, made a list of all my used modules and burned a dvd of the Drupal root directory. Now, after I've successfully restored the database of 5/6 sites, three modules report missing inter-module dependencies within their module groups:


Event- Calendar Signup   - 6.x-2.x-dev - Depends on: Signup
(missing)
Rules- Rules Simpletest - 6.x-1.4 - Depends on: Simpletest
(missing)
Services - 

servers - REST Server - 6.x-3.0-rc1    - Depends on:
Autoload (missing)
authentication - OAuth Authentication  6.x-3.0-rc1 - Depends on: Oauth_common (missing)



How can these other modules be missing if they were there before the migration? The folders are still the same. Do some modules "make" other modules in the database? Something like cTools 'makes' the css directory. 

All of my sites are in the sites directory and share the same modules, though they each have their own database. Each is missing the same module dependencies.
Are those missing modules in your sites/all/modules folder? I'm not sure why they would have been left out of a file migration, but anything's possible. 

Modules do not 'create' other modules (except possibly Features, I haven't used that in awhile) in the sense that you're referring to w/ the cTools example, though there are modules that exist as part of the parent module package.