An updated look at BPjs, the comprehensive BP platform.

1. BPjs Deep Dive 2019
4/4/2019, BGU

2. BPjs is
An extensible engine for
running and for analyzing
behavioral programs
Intended to be our industrial quality BP platform

3. BPjs is
An extensible engine for
running and for analyzing
behavioral programs
Intended to be our industrial quality BP platform
(...until something better is created)

5. James Birnie, ThoughtWorks
I tried to imagine as I was watching the demo how I could
have written the same program using techniques that I'm
most familiar with. Which probably means some kind of C#,
OOP based, implementation.
Whichever way I thought about it, I couldn't imagine a more
succinct, elegant version than that which was
demonstrated. As ever with succinct code I do wonder how
easy it would be to read by others without the (excellent)
explanation of what was going on.
http://www.jamesbirnie.com/2018/11/devoxx-belgium-and-two-talks.html

6. Using BPjs
• Command-line
For testing and experimenting with BP
• Maven
For maven-based JVM projects
• Uber-Jar
Has all the dependencies, may cause class duplication
• Jar
Just BPjs, but bring your own Rhino

7. https://github.com/bThink-BGU/BPjs

9. Command-line
• Download BPjs uber-jar
java -jar BPjs-0.10.3.uber.jar file1 file2 file3
java -jar BPjs-0.10.3.uber.jar file1 - file2
stdin

10. Maven (+Similar)
<dependencies>
...
<dependency>
<groupId>com.github.bthink-bgu</groupId>
<artifactId>BPjs</artifactId>
<version>0.10.3</version>
</dependency>
...
</dependencies>
• Preferred way for embedding in Java/JVM applications
• Stored at Maven Central

11. Jar/Uber-Jar
• Bring into class path
• Useful for using modi
fi
ed versions of BPjs
• (not recommended)

12. Application Lifecycle
BP CycleBPjs Program Start
Event
Selected
Synchronization
Point
B-threads
Arbiter
Event Selection Strategy
x✔/✘
B-Program
Start
B-thread
Registration
B-threads
.JS
start
x
bp.registerBThread(…)

13. Application Lifecycle
BP CycleBPjs Program Start
Event
Selected
Synchronization
Point
B-threads
Arbiter
Event Selection Strategy
x✔/✘
B-Program
Start
B-thread
Registration
B-threads
.JS
start
x
bp.registerBThread(…)
1

14. Application Lifecycle
BP CycleBPjs Program Start
Event
Selected
Synchronization
Point
B-threads
Arbiter
Event Selection Strategy
x✔/✘
B-Program
Start
B-thread
Registration
B-threads
.JS
start
x
bp.registerBThread(…)
1
2

15. Application Lifecycle
BP CycleBPjs Program Start
Event
Selected
Synchronization
Point
B-threads
Arbiter
Event Selection Strategy
x✔/✘
B-Program
Start
B-thread
Registration
B-threads
.JS
start
x
bp.registerBThread(…)
1
2 3

16. Application Lifecycle
BP CycleBPjs Program Start
Event
Selected
Synchronization
Point
B-threads
Arbiter
Event Selection Strategy
x✔/✘
B-Program
Start
B-thread
Registration
B-threads
.JS
start
x
bp.registerBThread(…)
1
2 3 4

17. Application Lifecycle
BP CycleBPjs Program Start
Event
Selected
Synchronization
Point
B-threads
Arbiter
Event Selection Strategy
x✔/✘
B-Program
Start
B-thread
Registration
B-threads
.JS
start
x
bp.registerBThread(…)
1
2 3 4
∞

18. bpjs
model
executionanalysis
started()
violationFound(Violation)
ended()
«abstract»
ProgressListener verify()
DfsBProgramVerifier
violation
VerificationResult
bthreadSnapshots
externalEvents
«serializable»
BProgramSyncSnapshot
prependCode(c)
appendCode(c)
externalEventQueue
globalScope
BProgram
selectableEvents(BProgamSyncSnapshot)
select(BProgamSyncSnapshot)
«abstract»
EventSelectionStrategyname:String
data:Object
BEvent
«waitFor»
«block»
start()
BProgramRunner
started(…)
eventSelected(e, …)
ended(…)
«abstract»
BProgramRunnerListener
isVisited(Node):Boolean
store(Node)
«abstract»
VisitedNodeStore
«produces»
inspectTrace( ExecutionTrace )
«abstract»
ExecutionTraceInspection
counterExample
«abstract»
Violation
Rhino continuation
synchronizationStatement
«serializable»
BThreadSyncSnapshot
request
waitFor
block
SyncStatement
1..*
contains(BEvent)
«abstract»
EventSet
1
nodes
ExecutionTrace
«produces»
«request»
1 1..* 1
0..*
1
1..*
2

19. No BThread class
• BThreads are emergent phenomenon of progression
between BThreadSyncSnaphots
BTSS BTSS BTSS BTSSStartBThread ResumeBThread ResumeBThread
ResumeBThread
BTSSBTSSBTSS
BTSS
ResumeBThreadResumeBThreadResumeBThread
Resume

20. bpjs
model
executionanalysis
started()
violationFound(Violation)
ended()
«abstract»
ProgressListener verify()
DfsBProgramVerifier
violation
VerificationResult
bthreadSnapshots
externalEvents
«serializable»
BProgramSyncSnapshot
prependCode(c)
appendCode(c)
externalEventQueue
globalScope
BProgram
selectableEvents(BProgamSyncSnapshot)
select(BProgamSyncSnapshot)
«abstract»
EventSelectionStrategyname:String
data:Object
BEvent
«waitFor»
«block»
start()
BProgramRunner
started(…)
eventSelected(e, …)
ended(…)
«abstract»
BProgramRunnerListener
Execution Host
isVisited(Node):Boolean
store(Node)
«abstract»
VisitedNodeStore
«produces»
inspectTrace( ExecutionTrace )
«abstract»
ExecutionTraceInspection
counterExample
«abstract»
Violation
Rhino continuation
synchronizationStatement
«serializable»
BThreadSyncSnapshot
request
waitFor
block
SyncStatement
1..*
contains(BEvent)
«abstract»
EventSet
1
nodes
ExecutionTrace
«produces»
«request»
1 1..* 1
0..*
1
1..*
Listener
«creates»
Verification Host
Listener
«creates»
2

22. VisualRunningExamples
• Sample BPjs application
• MDE
• Contains examples for
execution and veri
fi
cation

23. VisualRunningExamples
• Sample BPjs application
• MDE
• Contains examples for
execution and veri
fi
cation

24. VisualRunningExamples
• Sample BPjs application
• MDE
• Contains examples for
execution and veri
fi
cation

25. Model Driven Engineering
B-Program
(model)
B-Program Runner
Event Selection
Strategy
Input
Output
Long running processes
"Mainstream" System

26. Model Driven Engineering
B-Program
(model)
B-Program Runner
Event Selection
StrategyComplex, but
veri
fi
able.
Input
Output
Long running processes
"Mainstream" System

27. Model Driven Engineering
B-Program
(model)
B-Program Runner
Event Selection
Strategy
Simple
Complex, but
veri
fi
able.
Input
Output
Long running processes
"Mainstream" System

29. Parsing into B-Threads - Code
function parseMaze(mazeLines) {
for ( var row=0; row<mazeLines.length; row++ ) {
for ( var col=0; col<mazeLines[row].length; col++ ) {
var currentPixel =
mazeLines[row].substring(col,col+1);
if ( currentPixel===" " ||
currentPixel==="t" ||
currentPixel==="s" ) {
addSpaceCell(col, row);
if ( currentPixel==="t" ) {
addTargetCell(col, row);
} else if ( currentPixel==="s" ) {
addStartCell(col, row);
}
}
}
}
}

30. Parsing into B-Threads - Code
function parseMaze(mazeLines) {
for ( var row=0; row<mazeLines.length; row++ ) {
for ( var col=0; col<mazeLines[row].length; col++ ) {
var currentPixel =
mazeLines[row].substring(col,col+1);
if ( currentPixel===" " ||
currentPixel==="t" ||
currentPixel==="s" ) {
addSpaceCell(col, row);
if ( currentPixel==="t" ) {
addTargetCell(col, row);
} else if ( currentPixel==="s" ) {
addStartCell(col, row);
}
}
}
}
}

31. Parsing into B-Threads - Code
function parseMaze(mazeLines) {
for ( var row=0; row<mazeLines.length; row++ ) {
for ( var col=0; col<mazeLines[row].length; col++ ) {
var currentPixel =
mazeLines[row].substring(col,col+1);
if ( currentPixel===" " ||
currentPixel==="t" ||
currentPixel==="s" ) {
addSpaceCell(col, row);
if ( currentPixel==="t" ) {
addTargetCell(col, row);
} else if ( currentPixel==="s" ) {
addStartCell(col, row);
}
}
}
}
}

32. Parsing into B-Threads - Code
function parseMaze(mazeLines) {
for ( var row=0; row<mazeLines.length; row++ ) {
for ( var col=0; col<mazeLines[row].length; col++ ) {
var currentPixel =
mazeLines[row].substring(col,col+1);
if ( currentPixel===" " ||
currentPixel==="t" ||
currentPixel==="s" ) {
addSpaceCell(col, row);
if ( currentPixel==="t" ) {
addTargetCell(col, row);
} else if ( currentPixel==="s" ) {
addStartCell(col, row);
}
}
}
}
}

33. Parsing into B-Threads - Code
"Di
ff
erent types of cells have di
ff
erent behaviors"
function parseMaze(mazeLines) {
for ( var row=0; row<mazeLines.length; row++ ) {
for ( var col=0; col<mazeLines[row].length; col++ ) {
var currentPixel =
mazeLines[row].substring(col,col+1);
if ( currentPixel===" " ||
currentPixel==="t" ||
currentPixel==="s" ) {
addSpaceCell(col, row);
if ( currentPixel==="t" ) {
addTargetCell(col, row);
} else if ( currentPixel==="s" ) {
addStartCell(col, row);
}
}
}
}
}

34. Behaviors for a Space Cell
function addSpaceCell( col, row ) {
bp.registerBThread("cell(c:"+col+" r:"+row+")",
function() {
while ( true ) {
bp.sync({waitFor:adjacentCellEntries(col, row)});
bp.sync({
request: enterEvent(col, row),
waitFor: anyEntrance
});
}
}
);
}
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "];

35. Behaviors for a Space Cell
function addSpaceCell( col, row ) {
bp.registerBThread("cell(c:"+col+" r:"+row+")",
function() {
while ( true ) {
bp.sync({waitFor:adjacentCellEntries(col, row)});
bp.sync({
request: enterEvent(col, row),
waitFor: anyEntrance
});
}
}
);
}
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "];

36. Behaviors for a Space Cell
function addSpaceCell( col, row ) {
bp.registerBThread("cell(c:"+col+" r:"+row+")",
function() {
while ( true ) {
bp.sync({waitFor:adjacentCellEntries(col, row)});
bp.sync({
request: enterEvent(col, row),
waitFor: anyEntrance
});
}
}
);
}
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "];

37. Behaviors for a Target Cell
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "]
+function addTargetCell(col, row) {
bp.registerBThread("Target(c:"+col+" r:"+row+")", function(){
bp.sync({
waitFor: enterEvent(col, row)
});
bp.sync({
request: TARGET_FOUND,
block: bp.allExcept( TARGET_FOUND )
});
});
}
function addSpaceCell( col, row ) {...}

38. Behaviors for a Target Cell
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "]
+function addTargetCell(col, row) {
bp.registerBThread("Target(c:"+col+" r:"+row+")", function(){
bp.sync({
waitFor: enterEvent(col, row)
});
bp.sync({
request: TARGET_FOUND,
block: bp.allExcept( TARGET_FOUND )
});
});
}
function addSpaceCell( col, row ) {...}

39. Behaviors for a Target Cell
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "]
+function addTargetCell(col, row) {
bp.registerBThread("Target(c:"+col+" r:"+row+")", function(){
bp.sync({
waitFor: enterEvent(col, row)
});
bp.sync({
request: TARGET_FOUND,
block: bp.allExcept( TARGET_FOUND )
});
});
}
function addSpaceCell( col, row ) {...}

40. Behaviors for a Target Cell
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "]
+function addTargetCell(col, row) {
bp.registerBThread("Target(c:"+col+" r:"+row+")", function(){
bp.sync({
waitFor: enterEvent(col, row)
});
bp.sync({
request: TARGET_FOUND,
block: bp.allExcept( TARGET_FOUND )
});
});
}
function addSpaceCell( col, row ) {...}

41. Behaviors for a Start Cell
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "]
+
function addSpaceCell( col, row ) {...}
function addStartCell(col, row) {
bp.registerBThread("starter(c:"+col+" r:"+row+")",
function() {
bp.sync({
request:enterEvent(col,row)
});
});
}

42. Behaviors for a Start Cell
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "]
+
function addSpaceCell( col, row ) {...}
function addStartCell(col, row) {
bp.registerBThread("starter(c:"+col+" r:"+row+")",
function() {
bp.sync({
request:enterEvent(col,row)
});
});
}

43. Behaviors for a Start Cell
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "]
+
function addSpaceCell( col, row ) {...}
function addStartCell(col, row) {
bp.registerBThread("starter(c:"+col+" r:"+row+")",
function() {
bp.sync({
request:enterEvent(col,row)
});
});
}

44. Behaviors for a Start Cell
[" # t ",
"## ## ###",
" ",
"### #### ",
" s# "]
+
function addSpaceCell( col, row ) {...}
function addStartCell(col, row) {
bp.registerBThread("starter(c:"+col+" r:"+row+")",
function() {
bp.sync({
request:enterEvent(col,row)
});
});
}

45. Execution
private void runBprogram() {
// UI stuff
setInProgress(true);
//...
// Setup the b-program from the source
BProgram bprog = new StringBProgram(programEditor.getText());
bprog.setWaitForExternalEvents( true );
bprogramRunner = new BProgramRunner(bprog);
// add the maze
String mazeJs = mazeTableModel.getRows().stream()...
bprog.prependSource(mazeJs);
bprogramRunner.addListener(new BProgramRunnerListenerImpl(this));
// set pausing ESS
PausingEventSelectionStrategyDecorator pausingESS =
new PausingEventSelectionStrategyDecorator(
new SimpleEventSelectionStrategy());
bprog.setEventSelectionStrategy(pausingESS);
pausingESS.setListener( pess -> {

46. bprog.prependSource(mazeJs);
bprogramRunner.addListener(new BProgramRunnerListenerImpl(this));
// set pausing ESS
PausingEventSelectionStrategyDecorator pausingESS =
new PausingEventSelectionStrategyDecorator(
new SimpleEventSelectionStrategy());
bprog.setEventSelectionStrategy(pausingESS);
pausingESS.setListener( pess -> {
try {
Thread.sleep(150);
pess.unpause();
} catch (InterruptedException ex) {
System.err.println("Interrupted during event pause");
}
});
// go!
new Thread(()->{
try{
bprogramRunner.run();
} catch ( Exception e ) {
e.printStackTrace(System.out);
addToLog(e.getMessage());
setInProgress(false);
}
}).start();
}

47. class BProgramRunnerListenerImpl implements BProgramRunnerListener {
private final MainWindowCtrl mwCtrl;
public BProgramRunnerListenerImpl(final MainWindowCtrl mwCtrl) {
this.mwCtrl = mwCtrl;
}
@Override
public void starting(BProgram bprog) {
mwCtrl.addToLog("Starting...");
}
@Override
public void eventSelected(BProgram bp, BEvent theEvent) {
SwingUtilities.invokeLater(() -> {
String eventName = theEvent.getName();
if (eventName.startsWith("Enter")) {
String[] comps = eventName.substring(7).split(",");
comps[1] = comps[1].replace(")", "");
mwCtrl.mazeTableModel.addCellEntry(...);
}
mwCtrl.addToLog("Event: " + theEvent.toString());
});
}
}

48. Verifi cation
private void verifyBProgram() {
setInProgress(true);
stopBtn.setEnabled(false);
BProgram bprog = new StringBProgram(programEditor.getText() );
// add the maze
String mazeJs = mazeTableModel.getRows().stream()...collect(...);
bprog.prependSource(mazeJs);
// Mix in the assumptions and requirements
bprog.appendSource(additionsEditor.getText());
DfsBProgramVerifier vfr = new DfsBProgramVerifier();
vfr.setIterationCountGap(100);
vfr.addInspection( ExecutionTraceInspections.FAILED_ASSERTIONS );
vfr.addInspection( ExecutionTraceInspections.HOT_BPROGRAM_CYCLES );
vfr.setProgressListener( new DfsBProgramVerifier.ProgressListener() {
@Override
public void started(DfsBProgramVerifier v) {
addToLog("Verification started");
}
@Override

49. vfr.addInspection( ExecutionTraceInspections.HOT_BPROGRAM_CYCLES );
vfr.setProgressListener( new DfsBProgramVerifier.ProgressListener() {
@Override
public void started(DfsBProgramVerifier v) {
addToLog("Verification started");
}
@Override
public void iterationCount(long count, long statesHit, DfsBProgramVerifier v){
addToLog(" ~ "+count+" iterations, "+statesHit+" states visited.");
}
@Override
public void maxTraceLengthHit(List<DfsTraversalNode> trace,
DfsBProgramVerifier v) {
addToLog(" (max trace length hit)");
}
@Override
public void done(DfsBProgramVerifier v) {
addToLog("Verification done");
setInProgress(false);
}
@Override
public boolean violationFound(Violation aViolation, DfsBProgramVerifier vfr) {
return false; // do not continue searching,
}
});
logModel.clear();
mazeTableModel.resetCellEntries();

50. addToLog("Verification done");
setInProgress(false);
}
@Override
public boolean violationFound(Violation aViolation, DfsBProgramVerifier vfr) {
return false; // do not continue searching,
}
});
logModel.clear();
mazeTableModel.resetCellEntries();
// go!
new Thread(()->{
try{
VerificationResult res = vfr.verify(bprog);
SwingUtilities.invokeLater(()->setVerificationResult(res));
} catch ( Exception e ) {
e.printStackTrace(System.out);
addToLog(e.getMessage());
setInProgress(false);
}
}).start();
}

52. bp.registerBThread("round", function(){
while( true ) {
bp.sync({request:bp.Event("A")});
bp.sync({waitFor:[bp.Event("B1"),
bp.Event("B2")]});
bp.sync({request:bp.Event("C")});
}
});
bp.registerBThread("round-s1", function(){
while( true ) {
bp.sync({waitFor:bp.Event("A")});
bp.sync({request:bp.Event("B1"),
waitFor:bp.Event("B2")});
}
});
bp.registerBThread("round-s2", function(){
while( true ) {
bp.sync({waitFor:bp.Event("A")});
bp.sync({request:bp.Event("B2"),
waitFor:bp.Event("B1")});
}
});
round.js
start
ff55dba7
3281e80f
A
6ac289d7
B1 B2
C

53. bpjs
model
executionanalysis
started()
violationFound(Violation)
ended()
«abstract»
ProgressListener verify()
DfsBProgramVerifier
violation
VerificationResult
bthreadSnapshots
externalEvents
«serializable»
BProgramSyncSnapshot
prependCode(c)
appendCode(c)
externalEventQueue
globalScope
BProgram
selectableEvents(BProgamSyncSnapshot)
select(BProgamSyncSnapshot)
«abstract»
EventSelectionStrategyname:String
data:Object
BEvent
«waitFor»
«block»
start()
BProgramRunner
started(…)
eventSelected(e, …)
ended(…)
«abstract»
BProgramRunnerListener
isVisited(Node):Boolean
store(Node)
«abstract»
VisitedNodeStore
«produces»
inspectTrace( ExecutionTrace )
«abstract»
ExecutionTraceInspection
counterExample
«abstract»
Violation
Rhino continuation
synchronizationStatement
«serializable»
BThreadSyncSnapshot
request
waitFor
block
SyncStatement
1..*
contains(BEvent)
«abstract»
EventSet
1
nodes
ExecutionTrace
«produces»
«request»
1 1..* 1
0..*
1
1..*
2