ProB Java API Tutorial: Difference between revisions

ProB 2.0 is currently experimental. This means that the implementation may change during the course of development. However, we have reached the point in development where some of the features have reached a certain level of stability. Therefore, we are writing this tutorial to explain what those features are.

How to get started developing with ProB 2.0

The source code for ProB 2.0 is available via GitHub. There is also a short guide available there which will help getting Eclipse set up so that you can get started with the development. On our bug tracker, you can view the features that we are currently working on and can submit new feature requests.

How to open the Groovy Shell

The ProB Groovy shell is available in the Eclipse application. To open it, select

Window > Show View > Other..

Then select

ProB > Groovy Console

and hit ok.

Open the ProB API from Source/JAR file

In order to access the console from source or from a JAR file, start the application with the parameters -s (short for --shell) and -local (which specifies that you are running the application from a local computer). This will start a web server at a given port (the default is 8080, but it increments the port number if a port is already active). The shell can then be accessed at the following address:

localhost:PORTNR/sessions/GroovyConsoleSession

How to load a model

Classical B

You can load a Classical B model into the groovy console using the api variable that is available. There is a method b_load that is available to load Classical B models. For example:

m = api.b_load("/home/pathToFile/example.mch")

will load example.mch into the variable m.

Event B

To load an Event B model into ProB, right click on the model and select

Start Animation / Model Checking

from the context menu that drops down.

You can also load Event B models into the API via the eventb_load command in the Api object. The eventb_load command accepts .bcm and .bcc files.

How to animate models

The Trace abstraction is available to carry out animations.

In The Console

There are several different ways that a new transition can be added to the current trace. The most important thing to remember is that each Trace object is completely immutable. This means that when you change a trace, you are actually getting a new Trace back. This means that when you carry out an animation step, you always have to make sure that you save the Trace object that is returned.

The simplest way to add a transition is to specify it with the name of the event to be executed and predicates to specify how the parameters for the event are to be allocated. Specifying no predicate will assume a predicate of "TRUE=TRUE" for the given event.

t = t.execute("new","pp=PID1")

If executing the event in a groovy environment (console or script), the event will be recognized as a method on the Trace class. This means that you can execute the event "new" as follows:

t = t.new("pp=PID1")

If you know the id that has been allocated by the ProB kernel to a given transition, this can be added via the "add" method. This will search the outgoing transitions from the current state and attempts to find one with a matching id. For instance, if operation 0 is among the enabled operations for the current state, then

t = t.add(0)

will add operation 0 to the current trace, create a new trace, and return it.

If you know the name and parameters combination for a specific transition, you can also add operations via operation name and a list of the parameters. For instance

t = t.addTransitionWith("new",["PID3"])

will add the transition new(PID3) to the trace.

It is also possible to execute any event by executing

t = t.anyEvent()

and it is also possible to execute any event with name "name". For instance,

t = t.anyEvent("name")

will execute any event with the name "name".

It also possible to move backwards and forwards within a trace.

Move backwards:

t = t.back()

Move forwards:

t = t.forward()

In The UI

In order to animate a loaded model in the UI, double-click on an enabled event in the Events view. Then, the resulting trace will automatically be loaded into the different views and it can be further animated. To move backwards and forwards in the trace, use the buttons in the upper right hand corner of the Events view.

How to switch from UI to groovy console

There is an easy way to switch from the UI to the groovy console and back. It all happens using the "animations" global variable in the groovy console. What is important to remember, is that in this case, there is no distinction between an animation and a trace.

From UI to Console

In the UI, switch to the Current Animations view. Here you can view the different animations that are available. If the desired animation is not available, double click on it in this view and it will be set as the current animation. Now, to move this animation from the UI to the groovy console, simply type

x = animations.getCurrentTrace()

into the groovy console and the current animation will be loaded into the variable x.

From the Console to the UI

If you have a trace saved into variable trace_0 in the groovy console, you can easily add it to the UI. Simply type

animations.addNewAnimation(trace_0)

into the groovy console and the trace will automatically be added to the list of current animations and all of the views will be updated.

How to carry out evaluations

It is very simple to evaluate strings in the groovy console. There is a build in eval method in both the Trace and the StateSpace. In the trace, you just need to specify a string and the parser that is needed to parse the string. The two parsers currently available are ClassicalB and EventB.For instance,

t.evalCurrent("x:NAT" as EventB)

will parse "x:NAT" using the Event B parser and then will evaluate it at the current state. The following code

t.evalCurrent("x:NAT" as ClassicalB)

will parse "x:NAT" using the Classical B parser and then will evaluate it at the current state.

The Trace class can also attempt to identify the correct parser for the formula in question. This means that for an EventBModel the EventB parser will be used, and for a ClassicalBModel, the ClassicalB parser will be used. In this case, calling the evalCurrent method with a String parameter will parse the String formula with the parser associated with the current formalism being animated. In this case

t.eval("x:NAT").

will identify which model type is being animated and choose the appropriate parser.

It is also possible to evaluate formulas on the SpaceSpace level. For instance, if space_0 is a StateSpace, you can evaluate a list of formulas by typing

space_0.eval(space_0[5],["x:NAT" as EventB,"y:NAT" as ClassicalB])

into the console. This will parse "x:NAT" with the Event B parser and "y:NAT" with the Classical B parser and then will evaluate them at the state with id 5. The parser is not implicit in the StateSpace, so it is important to specify it here. In order to evaluate a formula, you need to specify the StateId object that is associated with the desired id. To extract a StateId from a StateSpace, you can use the notation space[ID] where ID is either a String or an integer representing the StateId that you want to view.

How to convert between the main abstractions

There is a connection between all of the main abstractions. You can easily convert between them by using the as operator.

To convert between a Model and a StateSpace, use:

eventb = statespace_0 as EventBModel (if you are animating an Event B model)

or

classicalb = statespace_0 as ClassicalBModel (if you are animating ClassicalB).

The reverse translation is just as easy:

space = model as StateSpace

will return the StateSpace associated with model.

Conversion between a Trace and a StateSpace and between a Trace and Model are also simple. The following conversions are valid:

space = trace as StateSpace

trace = StateSpace as Trace

trace = model as Trace

model = trace as EventBModel or model = trace as ClassicalBModel

The only thing to mention is that every time you convert from a StateSpace or Model to a Trace, a new trace from the root state is created.

How to save a trace

ProB currently supports a mechanism to save a trace in a script so that the same trace can be recreated. We are currently working on some improvements to this mechanism, so expect it to change over the next period of time. Currently, it is possible to save a Trace as an XML trace by typing

TraceConverter.save(trace_0,"/pathToFile/fileName.xml")

into the console. This will create the XML file fileName.xml.

If you want to load this trace back into the console, there are two options available. You can convert the XML file to a Groovy closure that will then take a Model object and return a Trace with all of the operations specified in the XML file. This can be triggered by calling the method

TraceConverter.xmlToGroovy("/pathToFile/fileName.xml","/pathToFile/groovyScript.groovy")

You can then run the produced Groovy script and execute the resulting closure to restore your Trace

run /pathToFile/groovyScript.groovy

A script script_NUM will be produced. Then enter

trace = script_NUM(modelForThisTrace)

into the console, where modelForThisTrace is the model for which the trace should be executed.

Another option is to simply restore the Trace directly from the TraceConverter

trace = TraceConverter.restore(modelForThisTrace,"/pathToFile/fileName.xml")

How to run a groovy script

You can use the build in run command to run a groovy script. Simply type

run new File(pathToScript/script.groovy)

into the console.

How to animate with only the StateSpace abstraction

It is also possible to carry out animations without using a trace object.

To get the root vertex from StateSpace space_0, type:

st = space_0.root

from there, you can execute a chain of events. For instance,

st = st.anyEvent("new").anyEvent().new("pp=PID1").new()

So you can execute anyEvent with the method anyEvent(filter), where filter can be a String name, or a List of names. You can also execute an event with name "name", with the method name(predicate), where predicate is the predicate string intended to filter the solutions for the event. If there are no parameters, the predicate "TRUE = TRUE" will automatically be added.

How to use a different probcli binary for ProB2

You need to start ProB2 or the respective Java application with:

-Dprob.home=PATHTOPROBCLIFOLDER