Google Explains Index Selection During A Core Update

Gary specifically mentions the index selection process (where Google chooses what goes into the index) and canonicalization (choosing which URL represents the webpage when there are duplicates). those systems are independent from the “core updates”. think of core updates as playing with cooking ingredients: you change how much salt or msg you put in your stir fry and you can radically change the result. When talking about a search engine, patents describe them as a collection of engines, using the phrase “indexing engine” when talking about indexing. For example, in one patent illustration there’s an indexing engine, a ranking engine, and a score modification engine.