lization Paradigm in Service Delivery Platforms file formats [1,2,36] reveals that most of them already contain some contextual information (fields) that correspond to the context meta model proposed in [5]. Among these fields there are, for example, the IP Address, the DATE and TIME of the request, and the USER-AGENT (browser, operating system, etc). Log File Format. The log file format we used (see Table 10.2) is based on the W3C log file format [36] which is enough extensible (thanks to 10 W3C General Purpose Fields) to adapt it to various applications. Notice that this log file format defines two new fields only: C - action and C - device. The first one is well known in application server log files: it usually contains the id of the action (e.g., Buy) that user applies to a given content. The second field informs about the device used (e.g., a laptop, a mobile phone, a remote control, etc.). Among the log file format fields, five are contextual: Date: The domain of date is organized into a hierarchy in such a manner that we can know whether it is a working day or a weekend, holiday or not, and SO on. Time: A day is partitioned into periods that are organized into a hierarchy. The time can inform whether it is day, night, morning, afternoon, and SO on. Table 10.2 Log File Format Date on which the request was received by the server Time at which the request was received by the server cs-uri-stem Stem (path) component of the requested URI cs-uri-query Query component of the requested URI c-auth-id Name or identifier of the authenticated user cs-method HTTP method of the request IP address of the client making the request; May captures the location c-dns Resolved Domain Name System (DNS) hostname of the host (client) making the request cs(UserAgent) Information about the user agent (browser, OS, language) originating the request sessionId Sessionization of user activities C - Action User action on the content (buy, add to panel, delete, etc.) C - Device Captures material media (laptop, mobile phone, PDA, etc.) So