Petersen et al. provide several excellent definitions and results on strand graph semantics for DNA computation in this lengthy but technically very sound paper. They very carefully review the state of art and propose a future scope of the work.

The process calculus stated in section 2 is a well-established concept, and it can be reduced to a great extent by highlighting the basic syntax and semantics only. In appendix A, there is an introduction to DNA strand displacement, which is again a well-established technique and should not be discussed any further except for providing some references. The formal definition of a strand graph, as stated in definition 4, is very clear and attractive. In definition 5, the authors provide an encoding from a process to a strand graph. Though the semantics of definition 6 is very useful in understanding the behavior of a full system, there is no discussion on the utility of the strand graph semantics for modeling DNA strand displacement in a specific application domain like neural network computation with DNA strand displacement. The authors should have also provided the wet lab protocols and gel images for such a design study on a neural network using DNA strand displacement so that readers could appreciate the advantage of the modeling technique of strand graph semantics. Section 4 is the most exciting section, as it deals with implementations of the proposed concepts. The implementation procedure is very vividly explained.

As a whole, the work is a landmark approach to a general formal language for modeling and simulating the behavior of DNA strand displacement. The overall content of the paper is very important for nanoscale computing and will have a tremendous impact in the area of DNA computing.