The present invention contains a system and method for automatic, knowledge-based processing and structuring of information from universal marked-up documents (any type of documents that contain structural, presentational, and semantic information (such as tags) alongside content, e.g., SGML / XML / HTML based documents). The present invention has applications on the Internet, as well as on Intranets, Extranets and any other network based information sources. The core technology of the present invention is an offer processing system and method. The offer processing system collects, stores, processes, retrieves, and presents information, product or service offers. The system automatically aggregates offers from a very large number of information sites, and achieves this without requiring site-specific adjustments or knowledge about the specific organization of the offers' data in a particular site' s page. An optional feature of the present invention is a front-end system for presenting structured offers to users or third parties. An exemplary application of the offer processing system and method is a system and method for comparative shopping. This application is a very large-scale, automatic, comparative-shopping engine that aggregates product and service offerings from virtually any number of web merchants or service providers, both globally (Web-based) and locally (brick & mortar). Additional information aggregation includes elements like job offers, real estate offers, accommodation offers, B2B offers, etc.