||The proliferation of e-commerce applications and the associated complexity and diversity of their information sources have posed many critical problems for accessing, relating, and combining data stored in these multiple, possibly heterogeneous information sources. Answering queries in e-commerce environments is a complicated problem that involves selecting the relevant information sources and generating a query plan to retrieve and combine the data automatically.The traditional cost-based query optimization techniques are computationally expensive because of the high connection overheads, high computation time, financial charges, and temporary unavailability, as well as the other problems of manipulating sources with different data models, semantics, and access methods. In this paper, we address the problem of integrating Answering Queries Using Views (and more generally Query Folding) with Semantic Query Optimization into one optimizer that uses the semantics of the database in the form of integrity constraints to support the query processing and optimization in e-commerce environments.A mediated schema is designed. User queries are posed in terms of this mediated schema. To allow the mediator to retrieve data, each information source is wrapped by a component that translates the component database schema into a view definition defined over the global schema.