In any case, it includes a system to scrape search results from other engines, based on Apple's Sherlock search-engine descriptors. These descriptors are also used by Mozilla:
Just a note: we used to have exactly the same mechanism in Carrot2. Unfortunately this format does not make a clear distinction between title/ url/ snippet parts and stays at snippet granularity, so we additionally parsed each snippet with regular expressions... The problem that lies beneath is in terms-of-use which forbid automatic scraping of search results using these plugins... That's the main reason why we switched to public APIs, actually.
D.
