17. A method of processing text messages in a mobile environment, the method comprising: processing user text messages in a user messaging session with a mobile messaging application; characterizing a user cognitive load with a user state model based upon situational parameters, including vehicle sensor information for a vehicle driven by a user, wherein the situational parameters are dependent upon user action, wherein the situational parameters include passenger compartment environment and vehicle speed, determining a plurality of distraction levels from the situational parameters, wherein each of the plurality of distraction levels corresponds to the cognitive load of the user; wherein a first one of the distraction levels is based upon a first one of the situational parameters corresponding to the passenger compartment environment and a second one of the distraction levels is based upon the vehicle speed; and adjusting functional performance of the mobile messaging application based on the distraction levels, such that a first one of the plurality of distraction levels corresponds to no message playback at all and a second one of the plurality of distraction levels corresponds to not playing back a message having a low priority.
17. A method of processing text messages in a mobile environment, the method comprising: processing user text messages in a user messaging session with a mobile messaging application; characterizing a user cognitive load with a user state model based upon situational parameters, including vehicle sensor information for a vehicle driven by a user, wherein the situational parameters are dependent upon user action, wherein the situational parameters include passenger compartment environment and vehicle speed, determining a plurality of distraction levels from the situational parameters, wherein each of the plurality of distraction levels corresponds to the cognitive load of the user; wherein a first one of the distraction levels is based upon a first one of the situational parameters corresponding to the passenger compartment environment and a second one of the distraction levels is based upon the vehicle speed; and adjusting functional performance of the mobile messaging application based on the distraction levels, such that a first one of the plurality of distraction levels corresponds to no message playback at all and a second one of the plurality of distraction levels corresponds to not playing back a message having a low priority. 26. A method according to claim 17 , wherein the functional performance includes a messaging sequencing control functionality.