No human intervention or judgement is involved.
Crawlers work by following links on the pages they retrieve.
When you use AltaVista Search Engine, you search the entire index using keywords or phrases. Departmental units that run their own departmental servers will have to register the Web servers to have them indexed. Your site HAS TO BE indexed by AltaVista before you can retrieve any search results that match your site criteria. When in doubt, use lowercase text in your searches. When you enter a search term in lowercase text, AltaVista Search Engine finds both upper and lowercase results.