document: Predictive caching and prefetching of query results in search engines We study the caching of query result pages in Web search engines . Popular search engines receive millions of queries per day , and efficient policies for caching query results may enable them to lower their response time and reduce their hardware requirements . We present PDC ( probability driven cache ) , a novel scheme tailored for caching search results , that is based on a probabilistic model of search engine users . We then use a trace of over seven million queries submitted to the search engine AltaVista to evaluate PDC , as well as traditional LRU and SLRU based caching schemes . The trace driven simulations show that PDC outperforms the other policies . We also examine the prefetching of search results , and demonstrate that prefetching can increase cache hit ratios by 50 % for large caches , and can double the hit ratios of small caches . When integrating prefetching into PDC , we attain hit ratios of over 0.53 .
doc_bio_tags: O B O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O B O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O O