Resource types

I'm in the process of writing web service function that will add a url to a course. I've got the basic skeleton of the web service (input/output) but I'm lacking some detail for the 'create' part. The documentation here (http://docs.moodle.org/dev/Database_schema_introduction) has a partial diagram of the course/modules tables and how they relate to each other. However, where does the url table come into it? And what tables would I need to update? I do not have access to the database at this time.