- Web scale discovery services provide a single search box to search across a library's subscribed resources including journals, books, databases, and more. They index these resources upfront to provide fast search results compared to federated search which searches resources individually. - Key parameters for evaluating discovery services include coverage, relevance ranking methodology, metadata quality, search refinement options, value-added features, and customer support. Subject indexing can be improved through "platform blending" which leverages subject indexes from databases. - User studies have shown discovery services can improve search effectiveness for users compared to individual library databases or Google Scholar. Local support from the discovery service provider is important.