In this paper, TEL 2010 action logs are analyzed with a particular focus on the impact of language (user native language and interface language) on the success of a search session. Particular user actions are defined as success indicators for searches and sessions are divided into “successful” and “unsuccessful” sessions with respect to their outcomes. Two approaches for studying the impact of the language of the search interface are pursued: (1) the effect of concurrent language choice when associating the user language (determined by IP address) with the interface language and (2) the consequences of interface language changes during a session. The challenges of country and language identification via IP addresses are also discussed
