Comparison shopping allows customers to reduce time and effort when searching for product information and prices. However, traditional comparison sites mainly compare product prices without using precise information on delivery cost. To overcome this limitation, we adopted a rule-based comparison shopping framework using the eXtensible Rule Markup Language (XRML) architecture, which computes the exact personalized delivery cost at comparison sites. The prototype ConsiderD, which was developed for this purpose, computes the exact delivery costs considering the shipping rules, destination, delivery speed, and shipping rates. The XRML architecture effectively maintains the consistency of formal rules with the original Web pages. To demonstrate the performance of rule-based comparisons, we conducted an experiment on the purchase of books based on real-world data from five leading online bookstores. This experiment shows that rule-based comparison can significantly outperform data-based comparison in terms of the total cost of product and delivery. We also found that the comparison of delivery cost is very important because the variance of delivery cost can be as big as the variance of book prices itself. (C) 2011 Elsevier B. V. All rights reserved.