The use of rules in business modeling is becoming more and more important, in applications requiring dynamic change of behavior. A number of rule languages and tools have been proposed to the software engineering community. However, there are not too many visual languages for rule modeling. The goal of this paper is to investigate the modeling capabilities of UML-based Rule Modeling Language (URML) with respect of Drools rules. We choose Drools because is the most important and well known open source rule platform. It is friendly to both developers and business users, offers a lot of functionality but does not provide a visual modeling environment for rules. The Single Item English Electronic Auction Use Case is used to illustrate the modeling capabilities. The paper concludes that URML rules can model the large part of Drools rules but improvements of the modeling language are necessary.