1. A method of applying role based association to entities in textual documents, the method comprising: obtaining a plurality of textual documents describing a plurality of entities; identifying a relationship between entities and verbs, at least on a sentence level, based on a semantic analysis of the verbs; determining at least one of: a topic, and a sentiment associated to the verbs identified in said textual documents or to sentences associated with said verbs; using the identified relationship between entities and verbs and a respective determined topic or sentiment associated with the verbs, to determine for each of the plurality of entities: a sentiment level associated thereto, and a level of activity at the at least one topic associated thereto; applying a probabilistic model of the topics presented in the textual documents while using the identified relationship between entities and verbs and a respective determined topic or sentiment associated with the verbs to determine for each of the plurality of entities: a sentiment level associated thereto, and a level of activity at the at least one topic associated thereto, taking into account a probability of each of the topic in a respective sentence, wherein the probabilistic model at the sentence level is based on an approximated probability of for each of the topics occurring in each of the sentences, calculated based on a probability of each of the topics occurring in each of the textual documents and a probability of a word occurring in each of the topics, and wherein the level of activity for each entity in the at least one topic is calculated as a sum of the approximated proportions of all of the topics in all of the sentences in the textual documents using, whenever the entity is tagged as active.
5. The method according to claim 1 , wherein the determining a sentiment associated to the verbs identified in textual documents is carried out using a dictionary or a trained learning algorithm.