15. The computer-readable storage medium of claim 11 , wherein changes in one or more contextual data of a foreground knowledge graph triggers using the set of arguments to perform an action for the user based on the user's context.
11. A non-transitory computer-readable storage medium storing instructions that when executed by a computer cause the computer to perform a method for providing context-based web services to a user, the method comprising: receiving, by the computer, general knowledge and domain-specific knowledge extracted from a body of content; training a model, using the received knowledge as input, based on machine learning to obtain a database which maps sentence structures to instructions on how to extract parameters from a sentence which corresponds to a respective sentence structure, wherein a respective sentence structure indicates an action to be performed or a question-and-answer sentence, and wherein a parameter includes one or more of a subject, a verb, and an object; receiving a sentence as input from the user interacting with a visual interface that includes an animated agent; determining a first sentence structure for the sentence based on the model; retrieving, from the database by using the first sentence structure as a key, instructions which are mapped to the first sentence structure and which indicate how to extract parameters from the sentence; extracting one or more parameters of the sentence based on the retrieved instructions and the first sentence structure; obtaining current and historical contextual data associated with the user; determining a set of arguments based on the parameters and the contextual data; and using the set of arguments to produce an audio response with a text-speech translator and determine mouth positions synchronized with the audio response to animate the animated agent.