9. A computer program product, comprising: a non-transitory computer readable storage device storing computer program instructions which, when processed by a computer system including at least one processor and a computer memory, enable the at least one processor to: access, in the computer memory, data identifying entities described in a document, wherein the document includes a plurality of tokens appearing in an order in the document, and data defining a sequence of sentiment values assigned to the tokens in the document, the sequence of sentiment values being in the order the corresponding tokens appear in the document, apply a filter to the sequence of sentiment values in the computer memory, the filter having a width defined by a number of tokens, such that the sentiment value of a token is spread among other nearby tokens within the width of the filter, whereby each entity has contributions due to sentiment values from nearby tokens within the width of the filter, and combine, for each entity in the document, the contributions from the nearby tokens to produce a sentiment value for the entity.
15. The computer program product of claim 9 , wherein the at least one processor is further configured to: receive data specifying an entity and sentiment information; determine, after a document is received, if the document includes the specified entity and sentiment information; and send a notification to a user if the document includes the specified entity and sentiment information.