1. A method of processing a plurality of linguistic expressions, each linguistic expression originating from an originator, and each linguistic expression being a linguistic expression in which the originator of that linguistic expression expresses a respective sentiment with respect to one or more topics, the method comprising: for each linguistic expression, detecting, by one or more processors, one or more topics of interest addressed in that linguistic expression by the originator of that linguistic expression; for each linguistic expression, for each topic detected in that linguistic expression, assessing, by the one or more processors, a sentiment of the originator of that linguistic expression with respect to that topic; grouping, by the one or more processors, the originators into one or more groups based on similarities between the originators' respective sets of detected topic-sentiment pairs; associating with a given group, by the one or more processors, semantic information, wherein the semantic information associated with the given group relates to one or more features selected from a group of features consisting of: properties of one or more members of that given group and the sets of topic-sentiment pairs of one or more of the members of that given group; and for a given originator, creating or updating, by the one or more processors, a profile; wherein the given originator is a member of the given group; wherein the profile is created or updated such that it comprises attributes of the given originator; and wherein the attributes are dependent upon the given originator's membership in the given group and the semantic information associated with the given group.
2. A method according to claim 1 : wherein each originator is a user of a network; wherein each linguistic expression is made available on the network, by its originator, to other users of the network; and wherein the network is selected from a group consisting of: the Internet, an intranet, a social network, and an online forum.