ColorUnfolder

This program implements the generalized Esparza/Römer/Vogler unfolding algorithm for high-level (colored) Petri nets. That is, an algorithm to find a finite complete prefix of the symbolic unfolding.

Other authors also use the term "unfolding" differently, to refer to the low-level net expressed through the high-level net. We call that low-level net the expansion of the high-level net and also implement an algorithm to calculate the expansion.

We also implement a just-in-time expansion algorithm for building the low-level unfolding of the expansion of a high-level net without building the expansion.

Features

• High-level net to symbolic unfolding
• High-level net to low-level unfolding
• High-level net to low-level expansion net
• Low-level net to low-level unfolding
• Finite complete prefix of unfolding using cut-offs
• Unfolding up to bounded depth
• Reachability of target transitions
• Command-line user interface
• Net parser (hllola format)
• Unfolding/prefix renderer
• Internal structure renderer
• Tuples

Non-goals

• Non-safe nets. We require the input net to be safe (1-bounded). That is, in every reachable marking there is at most one token on a place. Some authors call a high-level net 1-bounded if its expansion is 1-bounded. In the high-level net that is equivalent to every reachable marking having at most one token of every color on a place. Our requirement is stricter.

Related Tools

• Mole is a well known implementation of the Esparza/Römer/Vogler unfolding algorithm for low-level Petri nets.

• We use cvc5 or Z3 to decide the predicates.

Related Publications

• Nick Würdemann, Thomas Chatain, Stefan Haar, and Lukas Panneke. “Taking Complete Finite Prefixes to High Level, Symbolically”. In: Fundamenta Informaticae, vol. 192, iss. 3-4, pp. 313-361. doi: 10.3233/FI-242196. Open Access.
  Journal article about the theory and this tool.

• Nick Würdemann, Thomas Chatain, and Stefan Haar. “Taking Complete Finite Prefixes to High Level, Symbolically”. In: PETRI NETS ’23. LNCS 13929. 2023, pp. 123–144. doi: 10.1007/978-3-031-33620-1_7. Open Access.
  Introducing the algorithm for building complete finite prefixes of symbolic unfoldings for high-level Petri nets. This is our primary source.

• Thomas Chatain and Claude Jard. “Symbolic Diagnosis of Partially Observable Concurrent Systems”. In: FORTE ’04. LNCS 3235. 2004, pp. 326–342. doi: 10.1007/978-3-540-30232-2_21.
  Introducing symbolic unfoldings.

• Javier Esparza, Stefan Römer, and Walter Vogler. “An Improvement of McMillan’s Unfolding Algorithm”. In: Formal Methods in System Design 20.3 (2002), pp. 285–310. doi: 10.1023/A:1014746130920.
  Low-level unfolding algorithm that the symbolic approach is based on.

• Victor Khomenko and Maciej Koutny. “Branching Processes of High-Level Petri Nets”. In: TACAS ’03. LNCS 2619. 2003, pp. 458–472. doi: 10.1007/3-540-36577-X_34.
  Introducing an efficient algorithm to build complete finite prefixes of low-level unfoldings for high-level Petri nets.

Building on Linux

./get-cvc5.sh                 # install cvc5 with java bindings
./get-z3.sh                   # install z3 with java bindings
./gradlew buildExecutableApp  # build color-unfolder
./color-unfolder --help       # start using it

Bring your own net

There are two ways to have ColorUnfolder read in your net:

1. Give a file path or pipe a file into the program. The format supported by ColorUnfolder is similar to hllola, the high-level format of LoLA, a well known low-level Petri net analysis tool. The documentation of this format is found in the archive provided at LoLA's webpage. However, they seem to not be using the hllola format and instead rely on some other tool translating a high-level net into their low-level format.
2. Write your net as code. Since we care most about parametrized nets for our research, we generate all nets programmatically. The code for our nets is found in de.lukaspanneke.masterthesis.examples.Examples. To make the program aware of your net, add it to de.lukaspanneke.masterthesis.ui.Main#getBuiltinNet.