A server is disclosed for computing a score of an opinion that a message in a text file is expected to convey regarding a subject to be evaluated, wherein the message is written using literal strings and pictorial symbols. In this server, by the use of a pictorial-symbol dictionary memory storing a correspondence between designated pictorial-symbols to be rated and scores of opinions expressed by the respective pictorial-symbols, at least one of the used pictorial-symbols in the message which is coincident with at least one of the designated pictorial-symbols stored in the pictorial-symbol dictionary memory, is extracted from the message, at least one of the opinion scores which corresponds to the at least one extracted pictorial-symbol is retrieved within the pictorial-symbol dictionary memory, and an aggregate net opinion score for the message is calculated, based on an aggregate opinion score for the at least one extracted pictorial-symbol.