summaryrefslogtreecommitdiffstats
path: root/src/xmlpatterns/schema/qxsdparticlechecker.cpp
blob: fa26b8b9297a7aaa6ea680152cd2b6faef2db792 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
/****************************************************************************
**
** Copyright (C) 2008 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the QtXmlPatterns of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** No Commercial Usage
** This file contains pre-release code and may not be distributed.
** You may use this file in accordance with the terms and conditions
** contained in the either Technology Preview License Agreement or the
** Beta Release License Agreement.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/

#include "qxsdparticlechecker_p.h"

#include "qxsdelement_p.h"
#include "qxsdmodelgroup_p.h"
#include "qxsdschemahelper_p.h"
#include "qxsdstatemachine_p.h"
#include "qxsdstatemachinebuilder_p.h"
#include "qxsdtypechecker_p.h"

#include <QtCore/QFile>

QT_BEGIN_NAMESPACE

using namespace QPatternist;

namespace QPatternist
{
    /**
     * This template specialization is picked up by XsdStateMachine and allows us
     * to print nice edge labels.
     */
    template <>
    QString XsdStateMachine<XsdTerm::Ptr>::transitionTypeToString(XsdTerm::Ptr term) const
    {
        if (!term)
            return QLatin1String("(empty)");

        if (term->isElement()) {
            return XsdElement::Ptr(term)->displayName(m_namePool);
        } else if (term->isWildcard()) {
            const XsdWildcard::Ptr wildcard(term);
            return QLatin1String("(wildcard)");
        } else {
            return QString();
        }
    }
}

/**
 * This method is used by the isUPAConform method to check whether @p term and @p otherTerm
 * are the same resp. match each other.
 */
static bool termMatches(const XsdTerm::Ptr &term, const XsdTerm::Ptr &otherTerm, const NamePool::Ptr &namePool)
{
    if (term->isElement()) {
        const XsdElement::Ptr element(term);

        if (otherTerm->isElement()) {
            // both, the term and the other term are elements

            const XsdElement::Ptr otherElement(otherTerm);

            // if they have the same name they match
            if (element->name(namePool) == otherElement->name(namePool))
                return true;

        } else if (otherTerm->isWildcard()) {
            // the term is an element and the other term a wildcard

            const XsdWildcard::Ptr wildcard(otherTerm);

            // wildcards using XsdWildcard::absentNamespace, so we have to fix that here
            QXmlName name = element->name(namePool);
            if (name.namespaceURI() == StandardNamespaces::empty)
                name.setNamespaceURI(namePool->allocateNamespace(XsdWildcard::absentNamespace()));

            // if the wildcards namespace constraint allows the elements name, they match
            if (XsdSchemaHelper::wildcardAllowsExpandedName(name, wildcard, namePool))
                return true;
        }
    } else if (term->isWildcard()) {
        const XsdWildcard::Ptr wildcard(term);

        if (otherTerm->isElement()) {
            // the term is a wildcard and the other term an element

            const XsdElement::Ptr otherElement(otherTerm);

            // wildcards using XsdWildcard::absentNamespace, so we have to fix that here
            QXmlName name = otherElement->name(namePool);
            if (name.namespaceURI() == StandardNamespaces::empty)
                name.setNamespaceURI(namePool->allocateNamespace(XsdWildcard::absentNamespace()));

            // if the wildcards namespace constraint allows the elements name, they match
            if (XsdSchemaHelper::wildcardAllowsExpandedName(name, wildcard, namePool))
                return true;

        } else if (otherTerm->isWildcard()) {
            // both, the term and the other term are wildcards

            const XsdWildcard::Ptr otherWildcard(otherTerm);

            // check if the range of the wildcard overlaps.
            const XsdWildcard::Ptr intersectionWildcard = XsdSchemaHelper::wildcardIntersection(wildcard, otherWildcard);
            if (!intersectionWildcard ||
                (intersectionWildcard && !(intersectionWildcard->namespaceConstraint()->variety() != XsdWildcard::NamespaceConstraint::Not && intersectionWildcard->namespaceConstraint()->namespaces().isEmpty())))
                return true;
        }
    }

    return false;
}

/**
 * This method is used by the subsumes algorithm to check whether the @p derivedTerm is validly derived from the @p baseTerm.
 *
 * @param baseTerm The term of the base component (type or group).
 * @param derivedTerm The term of the derived component (type or group).
 * @param particles A hash to map the passed base and derived term to the particles they belong to.
 * @param context The schema context.
 * @param errorMsg The error message in the case that an error occurs.
 */
static bool derivedTermValid(const XsdTerm::Ptr &baseTerm, const XsdTerm::Ptr &derivedTerm, const QHash<XsdTerm::Ptr, XsdParticle::Ptr> &particles, const XsdSchemaContext::Ptr &context, QString &errorMsg)
{
    const NamePool::Ptr namePool(context->namePool());

    // find the particles where the base and derived term belongs to
    const XsdParticle::Ptr baseParticle = particles.value(baseTerm);
    const XsdParticle::Ptr derivedParticle = particles.value(derivedTerm);

    // check that an empty particle can not be derived from a non-empty particle
    if (derivedParticle && baseParticle) {
        if (XsdSchemaHelper::isParticleEmptiable(derivedParticle) && !XsdSchemaHelper::isParticleEmptiable(baseParticle)) {
            errorMsg = QtXmlPatterns::tr("empty particle cannot be derived from non-empty particle");
            return false;
        }
    }

    if (baseTerm->isElement()) {
        const XsdElement::Ptr element(baseTerm);

        if (derivedTerm->isElement()) {
            // if both terms are elements

            const XsdElement::Ptr derivedElement(derivedTerm);

            // check names are equal
            if (element->name(namePool) != derivedElement->name(namePool)) {
                errorMsg = QtXmlPatterns::tr("derived particle is missing element %1").arg(formatKeyword(element->displayName(namePool)));
                return false;
            }

            // check value constraints are equal (if available)
            if (element->valueConstraint() && element->valueConstraint()->variety() == XsdElement::ValueConstraint::Fixed) {
                if (!derivedElement->valueConstraint()) {
                    errorMsg = QtXmlPatterns::tr("derived element %1 is missing value constraint as defined in base particle").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }

                if (derivedElement->valueConstraint()->variety() != XsdElement::ValueConstraint::Fixed) {
                    errorMsg = QtXmlPatterns::tr("derived element %1 has weaker value constraint than base particle").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }

                const QSourceLocation dummyLocation(QUrl(QLatin1String("http://dummy.org")), 1, 1);
                const XsdTypeChecker checker(context, QVector<QXmlName>(), dummyLocation);
                if (!checker.valuesAreEqual(element->valueConstraint()->value(), derivedElement->valueConstraint()->value(), derivedElement->type())) {
                    errorMsg = QtXmlPatterns::tr("fixed value constraint of element %1 differs from value constraint in base particle").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }
            }

            // check that a derived element can not be nillable if the base element is not nillable
            if (!element->isNillable() && derivedElement->isNillable()) {
                errorMsg = QtXmlPatterns::tr("derived element %1 cannot be nillable as base element is not nillable").arg(formatKeyword(derivedElement->displayName(namePool)));
                return false;
            }

            // check that the constraints of the derived element are more strict then the constraints of the base element
            const XsdElement::BlockingConstraints baseConstraints = element->disallowedSubstitutions();
            const XsdElement::BlockingConstraints derivedConstraints = derivedElement->disallowedSubstitutions();
            if (((baseConstraints & XsdElement::RestrictionConstraint) && !(derivedConstraints & XsdElement::RestrictionConstraint)) ||
                ((baseConstraints & XsdElement::ExtensionConstraint) && !(derivedConstraints & XsdElement::ExtensionConstraint)) ||
                ((baseConstraints & XsdElement::SubstitutionConstraint) && !(derivedConstraints & XsdElement::SubstitutionConstraint))) {
                errorMsg = QtXmlPatterns::tr("block constraints of derived element %1 must not be more weaker than in the base element").arg(formatKeyword(derivedElement->displayName(namePool)));
                return false;
            }

            // if the type of both elements is the same we can stop testing here
            if (element->type()->name(namePool) == derivedElement->type()->name(namePool))
                return true;

            // check that the type of the derived element can validly derived from the type of the base element
            if (derivedElement->type()->isSimpleType()) {
                if (!XsdSchemaHelper::isSimpleDerivationOk(derivedElement->type(), element->type(), SchemaType::DerivationConstraints())) {
                    errorMsg = QtXmlPatterns::tr("simple type of derived element %1 cannot be validly derived from base element").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }
            } else if (derivedElement->type()->isComplexType()) {
                if (!XsdSchemaHelper::isComplexDerivationOk(derivedElement->type(), element->type(), SchemaType::DerivationConstraints())) {
                    errorMsg = QtXmlPatterns::tr("complex type of derived element %1 cannot be validly derived from base element").arg(formatKeyword(derivedElement->displayName(namePool)));
                    return false;
                }
            }

            // if both, derived and base element, have a complex type that contains a particle itself, apply the subsumes algorithm
            // recursive on their particles
            if (element->type()->isComplexType() && derivedElement->type()->isComplexType()) {
                if (element->type()->isDefinedBySchema() && derivedElement->type()->isDefinedBySchema()) {
                    const XsdComplexType::Ptr baseType(element->type());
                    const XsdComplexType::Ptr derivedType(derivedElement->type());
                    if ((baseType->contentType()->variety() == XsdComplexType::ContentType::ElementOnly ||
                        baseType->contentType()->variety() == XsdComplexType::ContentType::Mixed) &&
                        (derivedType->contentType()->variety() == XsdComplexType::ContentType::ElementOnly ||
                         derivedType->contentType()->variety() == XsdComplexType::ContentType::Mixed)) {

                        return XsdParticleChecker::subsumes(baseType->contentType()->particle(), derivedType->contentType()->particle(), context, errorMsg);
                    }
                }
            }

            return true;
        } else if (derivedTerm->isWildcard()) {
            // derive a wildcard from an element is not allowed
            errorMsg = QtXmlPatterns::tr("element %1 is missing in derived particle").arg(formatKeyword(element->displayName(namePool)));
            return false;
        }
    } else if (baseTerm->isWildcard()) {
        const XsdWildcard::Ptr wildcard(baseTerm);

        if (derivedTerm->isElement()) {
            // the base term is a wildcard and derived term an element

            const XsdElement::Ptr derivedElement(derivedTerm);

            // wildcards using XsdWildcard::absentNamespace, so we have to fix that here
            QXmlName name = derivedElement->name(namePool);
            if (name.namespaceURI() == StandardNamespaces::empty)
                name.setNamespaceURI(namePool->allocateNamespace(XsdWildcard::absentNamespace()));

            // check that name of the element is allowed by the wildcards namespace constraint
            if (!XsdSchemaHelper::wildcardAllowsExpandedName(name, wildcard, namePool)) {
                errorMsg = QtXmlPatterns::tr("element %1 does not match namespace constraint of wildcard in base particle").arg(formatKeyword(derivedElement->displayName(namePool)));
                return false;
            }

        } else if (derivedTerm->isWildcard()) {
            // both, derived and base term are wildcards

            const XsdWildcard::Ptr derivedWildcard(derivedTerm);

            // check that the derived wildcard is a valid subset of the base wildcard
            if (!XsdSchemaHelper::isWildcardSubset(derivedWildcard, wildcard)) {
                errorMsg = QtXmlPatterns::tr("wildcard in derived particle is not a valid subset of wildcard in base particle");
                return false;
            }

            if (!XsdSchemaHelper::checkWildcardProcessContents(wildcard, derivedWildcard)) {
                errorMsg = QtXmlPatterns::tr("processContent of wildcard in derived particle is weaker than wildcard in base particle");
                return false;
            }
        }

        return true;
    }

    return false;
}

typedef QHash<QXmlName, XsdElement::Ptr> ElementHash;

/**
 * Internal helper method that checks if the given @p particle contains an element with the
 * same name and type twice.
 */
static bool hasDuplicatedElementsInternal(const XsdParticle::Ptr &particle, const NamePool::Ptr &namePool, ElementHash &hash, XsdElement::Ptr &conflictingElement)
{
    const XsdTerm::Ptr term = particle->term();
    if (term->isElement()) {
        const XsdElement::Ptr mainElement(term);
        XsdElement::List substGroups = mainElement->substitutionGroups();
        if (substGroups.isEmpty())
            substGroups << mainElement;

        for (int i = 0; i < substGroups.count(); ++i) {
            const XsdElement::Ptr element = substGroups.at(i);
            if (hash.contains(element->name(namePool))) {
                if (element->type()->name(namePool) != hash.value(element->name(namePool))->type()->name(namePool)) {
                    conflictingElement = element;
                    return true;
                }
            } else {
                hash.insert(element->name(namePool), element);
            }
        }
    } else if (term->isModelGroup()) {
        const XsdModelGroup::Ptr group(term);
        const XsdParticle::List particles = group->particles();
        for (int i = 0; i < particles.count(); ++i) {
            if (hasDuplicatedElementsInternal(particles.at(i), namePool, hash, conflictingElement))
                return true;
        }
    }

    return false;
}

bool XsdParticleChecker::hasDuplicatedElements(const XsdParticle::Ptr &particle, const NamePool::Ptr &namePool, XsdElement::Ptr &conflictingElement)
{
    ElementHash hash;
    return hasDuplicatedElementsInternal(particle, namePool, hash, conflictingElement);
}

bool XsdParticleChecker::isUPAConform(const XsdParticle::Ptr &particle, const NamePool::Ptr &namePool)
{
    /**
     * The algorithm is implemented like described in http://www.ltg.ed.ac.uk/~ht/XML_Europe_2003.html#S2.2
     */

    // create a state machine for the given particle
    XsdStateMachine<XsdTerm::Ptr> stateMachine(namePool);

    XsdStateMachineBuilder builder(&stateMachine, namePool);
    const XsdStateMachine<XsdTerm::Ptr>::StateId endState = builder.reset();
    const XsdStateMachine<XsdTerm::Ptr>::StateId startState = builder.buildParticle(particle, endState);
    builder.addStartState(startState);

/*
    static int counter = 0;
    {
        QFile file(QString("/tmp/file_upa%1.dot").arg(counter));
        file.open(QIODevice::WriteOnly);
        stateMachine.outputGraph(&file, "Base");
        file.close();
    }
    ::system(QString("dot -Tpng /tmp/file_upa%1.dot -o/tmp/file_upa%1.png").arg(counter).toLatin1().data());
*/
    const XsdStateMachine<XsdTerm::Ptr> dfa = stateMachine.toDFA();
/*
    {
        QFile file(QString("/tmp/file_upa%1dfa.dot").arg(counter));
        file.open(QIODevice::WriteOnly);
        dfa.outputGraph(&file, "Base");
        file.close();
    }
    ::system(QString("dot -Tpng /tmp/file_upa%1dfa.dot -o/tmp/file_upa%1dfa.png").arg(counter).toLatin1().data());
*/
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateType> states = dfa.states();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > > transitions = dfa.transitions();

    // the basic idea of that algorithm is to iterate over all states of that machine and check that no two edges
    // that match on the same term leave a state, so for a given term it should always be obvious which edge to take
    QHashIterator<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateType> stateIt(states);
    while (stateIt.hasNext()) { // iterate over all states
        stateIt.next();

        // fetch all transitions the current state allows
        const QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > currentTransitions = transitions.value(stateIt.key());
        QHashIterator<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > transitionIt(currentTransitions);
        while (transitionIt.hasNext()) { // iterate over all transitions
            transitionIt.next();

            if (transitionIt.value().size() > 1) {
                // we have one state with two edges leaving it, that means
                // the XsdTerm::Ptr exists twice, that is an error
                return false;
            }

            QHashIterator<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > innerTransitionIt(currentTransitions);
            while (innerTransitionIt.hasNext()) { // iterate over all transitions again, as we have to compare all transitions with all
                innerTransitionIt.next();

                if (transitionIt.key() == innerTransitionIt.key()) // do no compare with ourself
                    continue;

                // use the helper method termMatches to check if both term matches
                if (termMatches(transitionIt.key(), innerTransitionIt.key(), namePool))
                    return false;
            }
        }
    }

    return true;
}

bool XsdParticleChecker::subsumes(const XsdParticle::Ptr &particle, const XsdParticle::Ptr &derivedParticle, const XsdSchemaContext::Ptr &context, QString &errorMsg)
{
    /**
     * The algorithm is implemented like described in http://www.ltg.ed.ac.uk/~ht/XML_Europe_2003.html#S2.3
     */

    const NamePool::Ptr namePool(context->namePool());

    XsdStateMachine<XsdTerm::Ptr> baseStateMachine(namePool);
    XsdStateMachine<XsdTerm::Ptr> derivedStateMachine(namePool);

    // build up state machines for both particles
    {
        XsdStateMachineBuilder builder(&baseStateMachine, namePool);
        const XsdStateMachine<XsdTerm::Ptr>::StateId endState = builder.reset();
        const XsdStateMachine<XsdTerm::Ptr>::StateId startState = builder.buildParticle(particle, endState);
        builder.addStartState(startState);

        baseStateMachine = baseStateMachine.toDFA();
    }
    {
        XsdStateMachineBuilder builder(&derivedStateMachine, namePool);
        const XsdStateMachine<XsdTerm::Ptr>::StateId endState = builder.reset();
        const XsdStateMachine<XsdTerm::Ptr>::StateId startState = builder.buildParticle(derivedParticle, endState);
        builder.addStartState(startState);

        derivedStateMachine = derivedStateMachine.toDFA();
    }

    QHash<XsdTerm::Ptr, XsdParticle::Ptr> particlesHash = XsdStateMachineBuilder::particleLookupMap(particle);
    particlesHash.unite(XsdStateMachineBuilder::particleLookupMap(derivedParticle));

/*
    static int counter = 0;
    {
        QFile file(QString("/tmp/file_base%1.dot").arg(counter));
        file.open(QIODevice::WriteOnly);
        baseStateMachine.outputGraph(&file, QLatin1String("Base"));
        file.close();
    }
    {
        QFile file(QString("/tmp/file_derived%1.dot").arg(counter));
        file.open(QIODevice::WriteOnly);
        derivedStateMachine.outputGraph(&file, QLatin1String("Base"));
        file.close();
    }
    ::system(QString("dot -Tpng /tmp/file_base%1.dot -o/tmp/file_base%1.png").arg(counter).toLatin1().data());
    ::system(QString("dot -Tpng /tmp/file_derived%1.dot -o/tmp/file_derived%1.png").arg(counter).toLatin1().data());
*/

    const XsdStateMachine<XsdTerm::Ptr>::StateId baseStartState = baseStateMachine.startState();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateType> baseStates = baseStateMachine.states();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > > baseTransitions = baseStateMachine.transitions();

    const XsdStateMachine<XsdTerm::Ptr>::StateId derivedStartState = derivedStateMachine.startState();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateType> derivedStates = derivedStateMachine.states();
    const QHash<XsdStateMachine<XsdTerm::Ptr>::StateId, QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > > derivedTransitions = derivedStateMachine.transitions();

    // @see http://www.ltg.ed.ac.uk/~ht/XML_Europe_2003.html#S2.3.1

    // define working set
    QList<QPair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId> > workSet;
    QList<QPair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId> > processedSet;

    // 1) fill working set initially with start states
    workSet.append(qMakePair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId>(baseStartState, derivedStartState));
    processedSet.append(qMakePair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId>(baseStartState, derivedStartState));

    while (!workSet.isEmpty()) { // while there are state sets to process

        // 3) dequeue on state set
        const QPair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId> set = workSet.takeFirst();

        const QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > derivedTrans = derivedTransitions.value(set.second);
        QHashIterator<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > derivedIt(derivedTrans);

        const QHash<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > baseTrans = baseTransitions.value(set.first);

        while (derivedIt.hasNext()) {
            derivedIt.next();

            bool found = false;
            QHashIterator<XsdTerm::Ptr, QVector<XsdStateMachine<XsdTerm::Ptr>::StateId> > baseIt(baseTrans);
            while (baseIt.hasNext()) {
                baseIt.next();
                if (derivedTermValid(baseIt.key(), derivedIt.key(), particlesHash, context, errorMsg)) {
                    const QPair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId> endSet =
                             qMakePair<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateId>(baseIt.value().first(), derivedIt.value().first());
                    if (!processedSet.contains(endSet) && !workSet.contains(endSet)) {
                        workSet.append(endSet);
                        processedSet.append(endSet);
                    }

                    found = true;
                }
            }

            if (!found) {
                return false;
            }
        }
    }

    // 5)
    QHashIterator<XsdStateMachine<XsdTerm::Ptr>::StateId, XsdStateMachine<XsdTerm::Ptr>::StateType> it(derivedStates);
    while (it.hasNext()) {
        it.next();

        if (it.value() == XsdStateMachine<XsdTerm::Ptr>::EndState || it.value() == XsdStateMachine<XsdTerm::Ptr>::StartEndState) {
            for (int i = 0; i < processedSet.count(); ++i) {
                if (processedSet.at(i).second == it.key() &&
                    (baseStates.value(processedSet.at(i).first) != XsdStateMachine<XsdTerm::Ptr>::EndState &&
                     baseStates.value(processedSet.at(i).first) != XsdStateMachine<XsdTerm::Ptr>::StartEndState)) {
                    errorMsg = QtXmlPatterns::tr("derived particle allows content that is not allowed in the base particle");
                    return false;
                }
            }
        }
    }

    return true;
}

QT_END_NAMESPACE