This is the website for VIATRA2/GRaTS, a stochastic graph transformation system simulator built in co-operation between the VIATRA2 Group and Dr. Paolo Torrini from Prof. Reiko Heckel's group at the University of Leicester.

GraTS implements a framework to run discrete-event stochastic simulations of semi-Markov processes based on generalised stochastic graph transformation. Graph transformation rules are used to define observable events that lead from one state to another (action rules), as well as quantitative observations over states (probe rules). GraTS enables the execution of structured simulation experiments made of multiple batches of bounded runs, allowing for variations in sensitive parameters that may include maximum length. It can compute statistics about action rule application, timing, probe rule values and covariance matrix, based on different forms of aggregation of the observations throughout an experiment.

GraTS is implemented in Java as a functionality of VIATRA2, a rule-based language interpreter based on abstract state machines and incremental pattern matching, available as an Eclipse plugin. GraTS relies on the implementation of graph transformation given by VIATRA2, taking advantage of incremental pattern matching to deal efficiently with semi-Markov processes. GraTS uses the SSJ libraries to deal with random number generation, distribution functions, confidence intervals and other statistics. GraTS also allows for the visualisation of individual runs, based on graph visualisation as provided in Eclipse by Zest

Obtaining GRaTS

Currently, GRaTS is only available as a set of source projects that you need to check out from SVN and then run an "Eclipse Application" run configuration from your workspace.

Requirements: Java 1.6.x, Eclipse 3.6, a recent version of VIATRA2

Check out everything from

Simulation project samples can then be checked out from


The most current documentation is attached to this page.


Hosted at BUTE

Hosted at ULE

  • Khan-Torrini-Heckel: Model-based Simulation of VoIP Network Reconfigurations using Graph Transformation Systems (ICGT2008) Download
  • Khan-Heckel-Torrini-Ráth: Model-based stochastic simulation of P2P VoIP using graph transformation system  Proceedings of the 17th international conference on Analytical and stochastic modeling techniques and applications ( ASMTA 2010) Download
  • Khan-Heckel: Model-based stochastic simulation of Super Peer Promotion in P2P VoIP using graph transformation  Proceedings of International Confrence on Data Communication Networking (DCNET 2011) (DBLP)