Department of Computer Science, Rice University, Houston, Texas, USA druths@rice.edu|Department of Computer Science, Rice University, Houston, Texas, USA druths@rice.edu|Department of Computer Science, Rice University, Houston, Texas, USA druths@rice.edu|Department of Computer Science, Rice University, Houston, Texas, USA druths@rice.edu|Department of Computer Science, Rice University, Houston, Texas, USA druths@rice.edu