1. A method for assisting a user to query for information available from information sources attached to a network, the method comprising: selecting the one or more information sources most relevant to a user query; formatting the user query for each relevant information source according to a description of each relevant information source written in a wrapper description language that comprises facilities for specifying an entire regular expression in terms of component regular expressions such that, upon recognition of one component regular expression of the entire regular expression, actions can be executed with variables bound as of the time of recognition of the component regular expression, the actions actually being executed only if the entire regular expression is also recognized; transmitting the formatted query to each of the relevant information sources; extracting data fields relevant to the user query from responses returned from the relevant information sources, according to the description of the relevant information source returning each response; and presenting the relevant data fields to the user.