add Volk's talk

_data/keynotes.yml

@@ -55,11 +55,27 @@
 - firstname: Matthias
   lastname: Volk
   photo: volk.png
-  title: TBD
+  title: Verification of Parametric Markov Chains
   affiliation: Eindhoven University of Technology, The Netherlands
   position: Assistant Professor
   website: https://volkm.github.io/
-  abstract: TBD
+  abstract: |
+    This talk presents verification approaches for parametric Markov chains in
+    both discrete-time and continuous-time.<br><br>
+
+    The first part presents an approach to synthesize optimal bias for Herman's
+    self-stabilizing token ring algorithm. The approach uses a parametric DTMC
+    and common parameter synthesis techniques to efficiently find optimal
+    parameter values. The results show that biased coins lead to faster
+    convergence than fair coins.<br><br>
+
+    The second part presents an analysis for CTMC with parametric transition
+    rates and a prior on the parameter values. Sampling the parameter values
+    from the prior distribution yields a non-parametric CTMC which can be
+    analysed with standard techniques. The approach employs a finite set of
+    parameter samples and a technique called scenario-optimization to yield
+    prediction regions. These regions contain the analysis results for any
+    additional sample point with high probability.
   bio: TBD
 
 - firstname: Gilles