As stated on their main website, the "DIMACS Implementation Challenges address questions of determining realistic algorithm performance where worst case analysis is overly pessimistic and probabilistic models are too unrealistic: experimentation can provide guides to realistic algorithm performance where analysis fails."
The 11th Implementation Challenge is dedicated to the study of Steiner Tree problems (broadly defined), bringing together research in both theory and practice. This edition of the challenge is co-organized by DIMACS (Center for Discrete Mathematics and Theoretical Computer Science) and ICERM (Institute for Computational and Experimental Research in Mathematics). The challenge is part of the DIMACS Special Focus on Information Sharing and Dynamic Data Analysis and will be capped by a workshop hosted by ICERM at Brown University in Providence, Rhode Island, in December 2014.