In E-commerce processes, various rules and constraints regarding product specifications, pricing, terms and conditions are exchanged between vendors and buyers. Developing a formal model for those rules and constraints gives a foundation for new E-commerce applications. Our approach is to develop a constraint database holding these conditions as dynamic constraints and provide a query language, called dynamic constraint algebra (DCA), for retrieving and matching business constraints. In this paper, we describe a system for processing DCA queries, its system architecture, constraint language, and graphical user interface for interactively querying over a database containing pricing and combination rules of products.