Google stemming mechanisms

In this study we investigated the stemming mechanisms of Google. We used its web interface and submitted many queries via a program. Stemming is the process of correlating morphologically similar words with one another. Search engines use stemming to match documents having one form of a word with queries having another form of the same word. We investigated the stemming mechanism of Google for three classes of words: singulars/plurals, combined words, and verbs with many postfixes. Our results indicate that Google uses a document-based algorithm for stemming. It evaluates each document separately and makes a decision to index or not for the conflated forms of the words it has. It indexes documents only for word forms that are semantically strongly correlated. While it indexes documents for singulars and plurals frequently, it rarely indexes documents for word forms with the postfixes of -able or -tively.