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Fixes and improvements for LTL2RabinLibrary DRA generation. 

Before, generating a DRA for L0 U L0 and bounded Until was broken.
The current code handles this and the other special case of L0 U !L0
correctly. Additionally, some small refactoring and comment improvements.


git-svn-id: https://www.prismmodelchecker.org/svn/prism/prism/trunk@10288 bbc10eb1-c90d-0410-af57-cb519fbb1720
master
Joachim Klein 11 years ago
parent
0e3c380e5e
commit
f9d02b349a
1 changed files with 228 additions and 104 deletions
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  1. 332
      prism/src/automata/LTL2RabinLibrary.java

332
prism/src/automata/LTL2RabinLibrary.java
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@ -139,15 +139,101 @@ public class LTL2RabinLibrary
// No time-bounded operators, do not convert using the library // No time-bounded operators, do not convert using the library
return null; return null;
} }
/** Helper class for storing info about an operand of a simple Until formula:
* Can be either TRUE, FALSE, a label or a negated label
*/
static class OperandInfo {
private String label;
private boolean notNegated;
/**
* Constructor: TRUE / FALSE
* @param value the value
**/
public OperandInfo(boolean value)
{
this.label = null;
notNegated = value;
}
/**
* Constructor: label or negated label
* @param label the label
* @param notNegated {@code true} if 'label', {@false} if '!label'
*/
public OperandInfo(String label, boolean notNegated)
{
this.label = label;
this.notNegated = notNegated;
}
/**
* Static constructor: Extract info from an Expression.
* Expression has to an ExpressionLabel or a boolean literal, possibly negated.
*/
public static OperandInfo constructFrom(Expression expr) throws PrismException
{
if (expr instanceof ExpressionLabel) {
return new OperandInfo(((ExpressionLabel)expr).getName(), true);
} else if (Expression.isNot(expr)) {
return constructFrom(((ExpressionUnaryOp)expr).getOperand()).negated();
} else if (expr instanceof ExpressionLiteral &&
((ExpressionLiteral) expr).getValue() instanceof Boolean) {
boolean b = (Boolean)((ExpressionLiteral)expr).getValue();
return new OperandInfo(b);
} else {
throw new PrismException("Unsupported expression "+expr+" in formula.");
}
}
/** Operand = TRUE? */
public boolean isTrue()
{
return label == null && notNegated;
}
/** Operand = FALSE? */
public boolean isFalse()
{
return label == null && !notNegated;
}
/** Operand = label or operand = !label? */
public boolean isProperLabel()
{
return label != null;
}
/** Get the label. Check first that {@code isProperLabel() == true}*/
public String getLabel()
{
assert(label != null);
return label;
}
/** Operand = !label? Check first that {@code isProperLabel() == true}*/
public boolean isLabelNegated()
{
assert(label != null);
return !notNegated;
}
/** Construct a negated version of this OperandInfo */
public OperandInfo negated()
{
return new OperandInfo(label, !notNegated);
}
}
/** /**
* Construct a prism.DA<BitSet,AcceptanceRabin> for the given until formula. * Construct a prism.DA<BitSet,AcceptanceRabin> for the given until formula.
* The expression is expected to have the form a U b, where
* a and b are either ExpressionLabels or true/false.
* The expression is expected to have the form A U B, where
* A and B are either ExpressionLabels or true/false, both possibly negated.
* The operator can have integer bounds. * The operator can have integer bounds.
* @param expr the until formula * @param expr the until formula
* @param constants values for constants (in bounds) * @param constants values for constants (in bounds)
* @param negated create DRA for the complement, i.e., !(a U b)
* @param negated create DRA for the complement, i.e., !(A U B)
*/ */
public static DA<BitSet,AcceptanceRabin> constructDRAForSimpleUntilFormula(ExpressionTemporal expr, Values constants, boolean negated) throws PrismException public static DA<BitSet,AcceptanceRabin> constructDRAForSimpleUntilFormula(ExpressionTemporal expr, Values constants, boolean negated) throws PrismException
{ {
@ -155,53 +241,28 @@ public class LTL2RabinLibrary
DA<BitSet,AcceptanceRabin> dra; DA<BitSet,AcceptanceRabin> dra;
if (expr.getOperator() != ExpressionTemporal.P_U) { if (expr.getOperator() != ExpressionTemporal.P_U) {
throw new PrismException("Not an Until operator!");
throw new PrismException("ConstructDRAForSimpleUntilFormula: Not an Until operator!");
} }
// get and check bounds information (non-negative, non-empty) // get and check bounds information (non-negative, non-empty)
bounds = IntegerBound.fromExpressionTemporal(expr, constants, true); bounds = IntegerBound.fromExpressionTemporal(expr, constants, true);
// extract information about the operands of the until operator, either a label (extracted to labelA)
// or true/false (stored in aBoolean, labelA=null).
String labelA, labelB;
boolean aBoolean = false, bBoolean = false;
// extract information about the operands of the until operator
OperandInfo opA, opB;
if (expr.getOperand1() instanceof ExpressionLabel) {
labelA = ((ExpressionLabel)expr.getOperand1()).getName();
} else {
if (expr.getOperand1() instanceof ExpressionLiteral &&
((ExpressionLiteral) expr.getOperand1()).getValue() instanceof Boolean) {
labelA = null;
aBoolean = (Boolean) ((ExpressionLiteral)expr.getOperand1()).getValue();
} else {
throw new PrismNotSupportedException("Unsupported expression "+expr.getOperand1()+" in formula.");
}
}
opA = OperandInfo.constructFrom(expr.getOperand1());
opB = OperandInfo.constructFrom(expr.getOperand2());
// do the same for the second operand.
if (expr.getOperand2() instanceof ExpressionLabel) {
labelB = ((ExpressionLabel)expr.getOperand2()).getName();
} else {
if (expr.getOperand2() instanceof ExpressionLiteral &&
((ExpressionLiteral) expr.getOperand2()).getValue() instanceof Boolean) {
labelB = null;
bBoolean = (Boolean) ((ExpressionLiteral)expr.getOperand2()).getValue();
} else {
throw new PrismNotSupportedException("Unsupported expression "+expr.getOperand2()+" in formula.");
}
}
// handle the special cases where one of the operands is true / false // handle the special cases where one of the operands is true / false
if (labelA == null && labelB == null) {
if (!opA.isProperLabel() && !opB.isProperLabel()) {
// bool U bool // bool U bool
boolean untilIsTrue; boolean untilIsTrue;
if (bBoolean == false) {
if (opB.isFalse()) {
// ? U false <=> false // ? U false <=> false
untilIsTrue = false; untilIsTrue = false;
} else { // bBoolean == true } else { // bBoolean == true
if (aBoolean == true) {
if (opA.isTrue()) {
// true U true <=> true // true U true <=> true
untilIsTrue = true; untilIsTrue = true;
} else { } else {
@ -210,56 +271,56 @@ public class LTL2RabinLibrary
untilIsTrue = bounds.isInBounds(0); untilIsTrue = bounds.isInBounds(0);
} }
} }
dra = constructDRAForTrue(null); dra = constructDRAForTrue(null);
if (!untilIsTrue) { if (!untilIsTrue) {
negated = !negated; negated = !negated;
} }
} else if (labelA == null) {
// first operand is boolean, second is normal label, bool U b
if (aBoolean) {
// true U_bounds b <=> F_bounds b
dra = constructDRAForFinally(labelB, false, bounds);
} else if (!opA.isProperLabel()) {
// first operand is boolean, second is label, bool U B
if (opA.isTrue()) {
// true U_bounds B <=> F_bounds B
dra = constructDRAForFinally(opB.getLabel(), opB.isLabelNegated(), bounds);
} else { } else {
// false U_bounds b <=> b in first step and first step in bounds
// false U_bounds B <=> B in first step and first step in bounds
if (bounds.isInBounds(0)) { if (bounds.isInBounds(0)) {
dra = constructDRAForInitialStateLabel(labelB);
dra = constructDRAForInitialStateLabel(opB.getLabel(), opB.isLabelNegated());
} else { } else {
// false // false
dra = constructDRAForTrue(labelB);
dra = constructDRAForTrue(opB.getLabel());
negated = !negated; negated = !negated;
} }
} }
} else if (labelB == null) {
// second operand is boolean, first is normal label, a U bool
if (!bBoolean) {
// a U false <=> false
dra = constructDRAForTrue(labelA);
} else if (!opB.isProperLabel()) {
// second operand is boolean, first is label, A U bool
if (opB.isFalse()) {
// A U false <=> false
dra = constructDRAForTrue(opA.getLabel());
negated = !negated; negated = !negated;
} else { } else {
if ((!bounds.hasLowerBound()) || if ((!bounds.hasLowerBound()) ||
(bounds.isInBounds(0))) { (bounds.isInBounds(0))) {
// a U_bounds true <=> true if there is no lower bound
// A U_bounds true <=> true if there is no lower bound
// or if lower bound is >=0 // or if lower bound is >=0
dra = constructDRAForTrue(labelA);
dra = constructDRAForTrue(opA.getLabel());
} else { } else {
// a U>=lower true
// <=> G<lower a
// <=> !(F<lower !a)
// A U>=lower true
// <=> G<lower A
// <=> !(F<lower !A)
// newBounds: >=lower becomes <lower // newBounds: >=lower becomes <lower
IntegerBound newBounds = new IntegerBound(null, false, IntegerBound newBounds = new IntegerBound(null, false,
bounds.getLowestInteger(), true); bounds.getLowestInteger(), true);
dra = constructDRAForFinally(labelA, true, newBounds);
dra = constructDRAForFinally(opA.getLabel(), !opA.isLabelNegated(), newBounds);
negated = !negated; negated = !negated;
} }
} }
} else { } else {
// the general case, a U_bounds b
dra = constructDRAForUntil(labelA, labelB, bounds);
// the general case, A U_bounds B
dra = constructDRAForUntil(opA.getLabel(), opA.isLabelNegated(),
opB.getLabel(), opB.isLabelNegated(), bounds);
} }
if (negated) { if (negated) {
// the constructed DRAs can be complemented by switching L and K // the constructed DRAs can be complemented by switching L and K
BitSet accL = (BitSet) dra.getAcceptance().get(0).getL().clone(); BitSet accL = (BitSet) dra.getAcceptance().get(0).getL().clone();
@ -274,90 +335,147 @@ public class LTL2RabinLibrary
return dra; return dra;
} }
/** Construct a DRA for a U_bounds b. Can be complemented by switching the acceptance sets. */
public static DA<BitSet, AcceptanceRabin> constructDRAForUntil(String labelA, String labelB, IntegerBound bounds)
/**
* Construct a DRA for A U_bounds B.
* Can be complemented by switching the acceptance sets.
* @param labelA the label of A
* @param aNegated is A negated?
* @param labelB the label of B
* @param bNegated is B negated?
*/
public static DA<BitSet, AcceptanceRabin> constructDRAForUntil(String labelA, boolean aNegated, String labelB, boolean bNegated, IntegerBound bounds)
{ {
DA<BitSet, AcceptanceRabin> dra; DA<BitSet, AcceptanceRabin> dra;
List<String> apList = new ArrayList<String>(); List<String> apList = new ArrayList<String>();
BitSet edge_ab, edge_Ab, edge_aB, edge_AB;
BitSet accL, accK;
/** Edge label for edge where first and second operand are false */
BitSet edge_ab = null;
/** Edge label for edge where first operand is true and second operand is false */
BitSet edge_Ab = null;
/** Edge label for edge where first operand is false and second operand is true */
BitSet edge_aB = null;
/** Edge label for edge where first and second operand are are true */
BitSet edge_AB = null;
/** Set of states contained in L part of Rabin pair */
BitSet accL;
/** Set of states contained in K part of Rabin pair */
BitSet accK;
int saturation = bounds.getMaximalInterestingValue(); int saturation = bounds.getMaximalInterestingValue();
// [0,saturation] + yes + no
// Construct states for [0,saturation] + yes + no
int states = saturation + 3; int states = saturation + 3;
apList.add(labelA); apList.add(labelA);
apList.add(labelB);
if (!labelA.equals(labelB)) {
// if the labels are equal, we only add the AP once
apList.add(labelB);
}
dra = new DA<BitSet,AcceptanceRabin>(states); dra = new DA<BitSet,AcceptanceRabin>(states);
dra.setAcceptance(new AcceptanceRabin()); dra.setAcceptance(new AcceptanceRabin());
dra.setAPList(apList); dra.setAPList(apList);
dra.setStartState(0); dra.setStartState(0);
edge_ab = new BitSet(); // !a & !b
edge_Ab = new BitSet(); // a & !b
edge_aB = new BitSet(); // !a & b
edge_AB = new BitSet(); // a & b
edge_Ab.set(0);
edge_aB.set(1);
edge_AB.set(0);
edge_AB.set(1);
if (labelA.equals(labelB)) {
// special treatment if the labels of a and b are the same...
if (aNegated == bNegated) {
edge_ab = new BitSet(); // !a & !b <=> !a
edge_ab.set(0, aNegated ? true : false);
edge_AB = new BitSet(); // a & b <=> a
edge_AB.set(0, aNegated ? false : true);
// the other edges are contradictory, we set them to null
// to ensure that they are ignored below
edge_Ab = null;
edge_aB = null;
} else {
edge_aB = new BitSet(); // !a & b <=> !a
edge_aB.set(0, aNegated ? true : false);
edge_Ab = new BitSet(); // a & !b <=> a
edge_Ab.set(0, aNegated ? false : true);
// the other edges are contradictory, we set them to null
// to ensure that they are ignored below
}
} else {
edge_ab = new BitSet(); // !a & !b
edge_ab.set(0, aNegated ? true : false);
edge_ab.set(1, bNegated ? true : false);
edge_Ab = new BitSet(); // a & !b
edge_Ab.set(0, aNegated ? false : true);
edge_Ab.set(1, bNegated ? true : false);
edge_aB = new BitSet(); // !a & b
edge_aB.set(0, aNegated ? true : false);
edge_aB.set(1, bNegated ? false : true);
edge_AB = new BitSet(); // a & b
edge_AB.set(0, aNegated ? false : true);
edge_AB.set(1, bNegated ? false : true);
}
// the index of the yes state
int yes_state = states - 2; int yes_state = states - 2;
// the index of the no states
int no_state = states - 1; int no_state = states - 1;
// generate the counter states for [0..saturation]
for (int counter = 0; counter <= saturation; counter++) { for (int counter = 0; counter <= saturation; counter++) {
int next_counter = counter + 1; int next_counter = counter + 1;
if (next_counter > saturation) next_counter = saturation; if (next_counter > saturation) next_counter = saturation;
if (bounds.isInBounds(counter)) { if (bounds.isInBounds(counter)) {
// b => yes
dra.addEdge(counter, edge_aB, yes_state);
dra.addEdge(counter, edge_AB, yes_state);
// B => yes
if (edge_aB != null) dra.addEdge(counter, edge_aB, yes_state);
if (edge_AB != null) dra.addEdge(counter, edge_AB, yes_state);
// !a & !b => no
dra.addEdge(counter, edge_ab, no_state);
// !A & !B => no
if (edge_ab != null) dra.addEdge(counter, edge_ab, no_state);
// a & !b => next_counter
dra.addEdge(counter, edge_Ab, next_counter);
// A & !B => next_counter
if (edge_Ab != null) dra.addEdge(counter, edge_Ab, next_counter);
} else { } else {
// !a => no
dra.addEdge(counter, edge_aB, no_state);
dra.addEdge(counter, edge_ab, no_state);
// !A => no
if (edge_aB != null) dra.addEdge(counter, edge_aB, no_state);
if (edge_ab != null) dra.addEdge(counter, edge_ab, no_state);
// a => next_counter
dra.addEdge(counter, edge_Ab, next_counter);
dra.addEdge(counter, edge_AB, next_counter);
// A => next_counter
if (edge_Ab != null) dra.addEdge(counter, edge_Ab, next_counter);
if (edge_AB != null) dra.addEdge(counter, edge_AB, next_counter);
} }
} }
// yes state = true loop // yes state = true loop
dra.addEdge(yes_state, edge_ab, yes_state);
dra.addEdge(yes_state, edge_aB, yes_state);
dra.addEdge(yes_state, edge_Ab, yes_state);
dra.addEdge(yes_state, edge_AB, yes_state);
if (edge_ab != null) dra.addEdge(yes_state, edge_ab, yes_state);
if (edge_aB != null) dra.addEdge(yes_state, edge_aB, yes_state);
if (edge_Ab != null) dra.addEdge(yes_state, edge_Ab, yes_state);
if (edge_AB != null) dra.addEdge(yes_state, edge_AB, yes_state);
// no state = true loop // no state = true loop
dra.addEdge(no_state, edge_ab, no_state);
dra.addEdge(no_state, edge_aB, no_state);
dra.addEdge(no_state, edge_Ab, no_state);
dra.addEdge(no_state, edge_AB, no_state);
if (edge_ab != null) dra.addEdge(no_state, edge_ab, no_state);
if (edge_aB != null) dra.addEdge(no_state, edge_aB, no_state);
if (edge_Ab != null) dra.addEdge(no_state, edge_Ab, no_state);
if (edge_AB != null) dra.addEdge(no_state, edge_AB, no_state);
// acceptance = // acceptance =
// infinitely often yes_state, // infinitely often yes_state,
// not infinitely often no_state or saturation state // not infinitely often no_state or saturation state
// this allows complementation by switching L and K.
// this allows complementing by switching L and K.
accL = new BitSet(); accL = new BitSet();
accL.set(no_state); accL.set(no_state);
accL.set(saturation); accL.set(saturation);
accK = new BitSet(); accK = new BitSet();
accK.set(yes_state); accK.set(yes_state);
dra.getAcceptance().add(new AcceptanceRabin.RabinPair(accL, accK)); dra.getAcceptance().add(new AcceptanceRabin.RabinPair(accL, accK));
return dra; return dra;
} }
/** /**
* Construct a DRA for LTL formula "F_bounds a". * Construct a DRA for LTL formula "F_bounds a".
* If {@code negateA == true}, constructs DRA for "F_bounds !a". * If {@code negateA == true}, constructs DRA for "F_bounds !a".
@ -418,16 +536,17 @@ public class LTL2RabinLibrary
// acceptance = // acceptance =
// infinitely often yes_state, // infinitely often yes_state,
// not infinitely often saturation state // not infinitely often saturation state
// this allows complementation by switching L and K.
// this allows complementing by switching L and K.
accL = new BitSet(); accL = new BitSet();
accL.set(saturation); accL.set(saturation);
accK = new BitSet(); accK = new BitSet();
accK.set(yes_state); accK.set(yes_state);
dra.getAcceptance().add(new RabinPair(accL, accK)); dra.getAcceptance().add(new RabinPair(accL, accK));
return dra; return dra;
} }
/** /**
* Construct a DRA that always accepts. * Construct a DRA that always accepts.
* If {@code label == null}, then there is no label, if {@code label != null} then * If {@code label == null}, then there is no label, if {@code label != null} then
@ -446,12 +565,17 @@ public class LTL2RabinLibrary
/** /**
* Construct a DRA that accepts if the first label corresponds to the provided label. * Construct a DRA that accepts if the first label corresponds to the provided label.
* If {@code negatedLabel == true} then automaton accepts if the word starts with the negated label.
* Can be complemented by switching the acceptance sets. * Can be complemented by switching the acceptance sets.
*/ */
public static DA<BitSet,AcceptanceRabin> constructDRAForInitialStateLabel(String label) throws PrismException {
public static DA<BitSet,AcceptanceRabin> constructDRAForInitialStateLabel(String label, boolean negatedLabel) throws PrismException {
List<String> labels = new ArrayList<String>(); List<String> labels = new ArrayList<String>();
labels.add(label); labels.add(label);
return createDRAFromString("3 states (start 0), 1 labels: 0-{0}->1 0-{}->2 1-{}->1 1-{0}->1 2-{}->2 2-{0}->2; 1 acceptance pairs: ({2},{1})", labels);
if (negatedLabel) {
return createDRAFromString("3 states (start 0), 1 labels: 0-{ }->1 0-{0}->2 1-{0}->1 1-{ }->1 2-{}->2 2-{0}->2; 1 acceptance pairs: ({2},{1})", labels);
} else {
return createDRAFromString("3 states (start 0), 1 labels: 0-{0}->1 0-{ }->2 1-{ }->1 1-{0}->1 2-{}->2 2-{0}->2; 1 acceptance pairs: ({2},{1})", labels);
}
} }
/** /**

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