PN-Suite is a system prepared to implement, combine, compare, and evaluate Petri net slicing algorithms. Roughly, this system can be seen as a workbench that implements the currently most important algorithms for Petri net slicing (it is prepared to easily integrate more algorithms into it). This system provides a new functionality that is particularly useful for the analysis and optimization of Petri nets: it combines all the slicing algorithms with the analysis of properties in such a way that one can reduce the size of a Petri net producing a slice that preserves some desired properties.
PN-Suite implements interfaces to communicate with other systems such as APT. This means that PN-Suite takes advantage of APT analyses to report about the properties kept or lost by the slices produced.
In the rest of this document we describe the main features and functionality of PN-Suite, and its architecture.
There are two prerequisites to use this tool. One is the (free) tool Graphviz, and the other is the (free) Erlang/OTP framework. These are the few steps needed to have PN-Suite installed in a Unix system.
$ git clone https://github.com/tamarit/pn_suite.git
$ cd pn_suite/
$ make
$ sudo make install
The first step clones the GitHub's repository content to the local system. Then, make is used to compile source files and, finally, three executables (pn_slicer, pn_prop, and pn_tools) are generated and installed by make install.
We have prepared a docker container for those users that are unable to find an environment that fullfils the intallation's requirements. To create the docker image simply run:
$ docker build -t pn_suite .
The next step is to run the container. To do so use thhe following command:
$ docker run --name pn -it -v $PWD/examples:/pn_suite/examples --rm pn_suite
Once inside the container the instruction to follow are the same as it is explanied in section Usage. The on-host examples' folder can be used to add your own petri nets or modify the existing ones. The outputs will be generated also there as explained in section Usage.
The three available commands are described in next sections.
This tool allows us to extract slices using one of the algorithms, or to extract all the slices (using all algorithms) that preserve a given set of properties
$ pn_slicer PNML_FILE SLICING_CRITERION [PROPERTY_LIST | SLICING_ALGORITHM] [-json]
where SLICING_CRITERION is a list of places separated with commas.
PROPERTY_LIST is optional. It accepts APT properties.
Valid APT properties are:
backwards_persistent
output_nonbranching
bicf
strongly_connected
free_choice
pure
plain
persistent
strongly_live
k-marking
s_net
nonpure_only_simple_side_conditions
bcf
num_tokens
asymmetric_choice
safe
weakly_live
restricted_free_choice
homogeneous
k-bounded
bounded
reversible
conflict_free
weakly_connected
num_places
num_arcs
simply_live
num_transitions
t_net
num_labels
isolated_elements
If not specified, all algorithms will be used.
To choose a slicing algorithm we have to write alg:ALGORITHM (no quotes required).
The names of the algorithms are:
rakow_ctl
rakow_safety
llorens_maximal
llorens_minimal
yu
An example of this usage is:
$ pn_slicer examples/other/pn_example.xml "P2,P7" alg:llorens_maximal
Petri net named example successfully read.
Slicing criterion: [P2, P7]
Slicing using Llorens et al. (maximal)
For instance, we can compute several slices with the following command (observe that they all preserve the property conflict_free.
$ pn_slicer examples/other/pn_example.xml "P6,P9" "conflict_free"
Petri net named pn_example successfully read.
Slicing criterion: [P6, P9]
1.- Llorens et al.'s slicer (maximal) -> Reduction: 9.09 %
2.- Rakow's slicer CTL -> Reduction: 0.00 %
3.- Yu et al.'s slicer -> Reduction: 13.64 %
4.- Rakow's slicer safety -> Reduction: 4.55 %
Each slice is stored in a file named output/<PNML_NAME>_<OUTPUT_NUMBER>.pnml. For example, Yu's slice generated above can be found at output/example_4.pnml. A pdf file is also generated. If flag -json is used, a JSON output is generated with exact details about locations and other relevant data.
$ pn_slicer examples/other/pn_example.xml "P6,P9" "conflict_free" -json
{
"slicing_criterion": [
{
"place": "P6"
},
{
"place": "P9"
}
],
"preserved_properties": [
{
"property": "conflict_free"
}
],
"warnings_parsing_slicing_criterion": "",
"warnings_parsing_properties": "",
"petri_net": {
"name": "example",
"file": "examples/other/pn_example.xml"
},
"slices": [
{
"algorithm": "llorens_maximal",
"reduction": "9.09",
"output_file": "output/example_2.pnml"
},
{
"algorithm": "rakow_ctl",
"reduction": "0.00",
"output_file": "output/example_3.pnml"
},
{
"algorithm": "yu",
"reduction": "13.64",
"output_file": "output/example_4.pnml"
},
{
"algorithm": "rakow_safety",
"reduction": "4.55",
"output_file": "output/example_5.pnml"
}
]
}
This tool allows us to study the preservation of properties of a slice.
$ pn_prop PNML_FILE PNML_FILE [PROPERTY_LIST]
Given two Petri nets (often a Petri net and its slice), it shows a list of properties that hold in both Petri nets, and a list of properties that only hold in the original Petri net. It is also possible to specify some specific properties, and only them will be analyzed. For the analysis of properties, pn_prop conveniently communicates with APT. With the information provided by these tools, it decides whether the required properties are preserved.
$ pn_prop pn_example.xml output/example_1.pnml
Preserved properties:
weakly_connected, output_nonbranching, strongly_connected, free_choice, pure,
plain, strongly_live, k-marking, s_net, nonpure_only_simple_side_conditions,
simply_live, t_net, weakly_live, restricted_free_choice, homogeneous,
isolated_elements, bounded, reversible, conflict_free
Changed properties:
backwards_persistent, num_places, bicf, persistent, bcf, num_tokens,
asymmetric_choice, num_arcs, num_transitions, num_labels, safe, k-bounded
For instance, code bellow shows that property simply_live is preserved between the two Petri nets given as arguments.
$ pn_prop pn_example.xml output/example_1.pnml "simply_live"
true
This tool is interactive and it can be used to animate a Petri net, slice it, or convert it to several formats.
$ pn_tools pn_example.xml
Petri net example successfully read.
These are the available options:
1 .- Run the Petri Net
2 .- Export the Petri Net
3 .- Slicing Llorens et al (maximal)
4 .- Slicing Llorens et al (minimal)
5 .- Slicing Llorens et al (for a given transition seq.)
6 .- Slicing Yu et al
7 .- Slicing Rakow CTL
8 .- Slicing Rakow Safety
What do you want to do?
[1/2/3/4/5/6/7/8]:
The Petri net can be animated either manually or randomly. If manual animation is chosen, the system iteratively shows the user the enabled transitions, and she can select the transitions that must be fired. The Petri net that is being animated can be found at output/<PN_NAME>_run.pdf (thus, an external PDF viewer can be used as a visual support). In this PDF the enabled transitions are highlighted in red, so the user can see them clearly. In the random animation we can specify the number n of random steps to be performed, and the Petri net fires n random transitions, or until no more transitions can be fired.
[1/2/3/4/5/6/7/8]: 1
Available modes:
0.- Manually
n.- n random steps (at most)
How do you want to run the PN? $ 10
Selected transition: T5
Selected transition: T9
Selected transition: T10
Selected transition: T7
Selected transition: T8
There is not any fireable transition.
Execution:
T5,T9,T10,T7,T8
The user can select from a menu a slicing algorithm. Then, according to the chosen algorithm, the user can specify a slicing criterion. The Petri net is then automatically sliced and a new Petri net (the slice) is produced. It is important to highlight that this tool implements another slicing algorithm (option 5) besides those of pn_slicer. This algorithm allows us to extract a slice from a Petri net considering a specific firing sequence (instead of all possible firing sequences as all the other algorithms do).
The output of PN-Suite can be produced in many different formats, including standard PNML (compatible with PIPE5), APT, DOT and more than 50 other formats provided by Graphviz.
[1/2/3/4/5/6/7/8]: $ 2
1 .- pdf
2 .- dot
3 .- PNML (compatible with PIPE)
4 .- APT
5 .- Other formats
What format do you need?
[1/2/3/4/5]: 1
Even though we strongly encourage all users to install PN-Suite, we have implemented an online web interface.