Scripting languages have gained popularity in video games for specifying the interactive content in a story. Game designers do not necessarily possess programming skills and often demand code-generating tools that can transform textual or graphical descriptions of interactions into scripts interpreted by the game engine. However, in event-based games, this code generation process may lead to potential inefficiencies and conflicts if there are multiple independent sources generating scripts for the same event. This thesis presents solutions to both perils: transformations to eliminate redundancies in the generated scripts and an advisory tool to provide assistance in detecting unintended conflicts. By incorporating traditional compiler techniques with an original code-redundancy-elimination approach, the code transformation is able to reduce code size by 25% on scripts and 14% on compiled byte-codes. With the proposed alternative view, the advisory tool is suitable for offering aid to expose potential script conflicts.

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XML files are frequently used by developers when building Web applications or Java EE applications. However, maintaining XML files is challenging and time-consuming because the correct usage of XML entities is always domain-specific and rarely well documented. Also, the existing compilers and program analysis tools seldom examine XML files. In this thesis, we developed a novel approach to XML file debugging called Xeditor where we extract XML consistency rules from open-source projects and use these rules to detect XML bugs. There are two phases in Xeditor: rule inference and application. To infer rules, Xeditor mines XML-based deployment descriptors in open-source projects, extracting XML entity pairs that frequently co-exist in the same files and refer to the same string literals. Xeditor then applies association rule mining to the extracted pairs. For rule application, given a program commit, Xeditor checks whether any updated XML file violates the inferred rules; if so, Xeditor reports the violation and suggests an edit for correction?. Our evaluation shows that Xeditor inferred rules with high precision (83%). For injected XML bugs, Xeditor detected rule violations and suggested changes with 74.6% precision, 50% recall. More importantly, Xeditor identified 31 really erroneous XML updates in version history, 17 of which updates were fixed by developers in later program commits. This observation implies that by using Xeditor, developers would have avoided introducing errors when writing XML files. Finally, we compared Xeditor with a baseline approach that suggests changes based on frequently co-changed entities, and found Xeditor to outperform the baseline for both rule inference and rule application. / XML files are frequently used in Java programming and when building Web application implementation. However, it is a challenge to maintain XML files since these files should follow various domain-specific rules and the existing program analysis tools seldom check XML files. In this thesis, we introduce a new approach to XML file debugging called Xeditor that extracts XML consistency rules from open-source projects and uses these rules to detect XML bugs. To extract the rules, Xeditor first looks at working XML files and finds all the pairs of entities A and B, which entities coexist in one file and have the same value on at least one occasion. Then Xeditor will check when A occurs, what is the probability that B also occurs. If the probability is high enough, Xeditor infers a rule that A is associated with B. To apply the rule, Xeditor checks XML files with errors. If a file violates the rules that were previously inferred, Xeditor will report the violation and suggest a change. Our evaluation shows that Xeditor inferred the correct rules with high precision 83%. More importantly, Xeditor identified issues in previous versions of XML files, and many of those issues were fixed by developers in later versions. Therefore, Xeditor is able to help find and fix errors when developers write their XML files.

<p>Diagnosis is the task of finding faults or malfunctioning components in a technical system, e.g a car. When doing diagnosis on cars with combustion engines, a computer program can be used. The computer program, also called diagnosis system, needs information about the car. This information could be data sheets of all the electronic components in the car. It could also be a description of how the engine behaves in a nominal and a non-nominal case. This information is contained in a model of the engine. RODON, a diagnostic tool developed by Sörman Information and Media AB, uses models of systems for conflict detection diagnosis. RODON needs fault models of the components to do diagnosis. The diagnosis system is then used in workshops, factories, or other places where cars need to be surveyed.</p><p>In this thesis, a Simulink model of the nominal behaviour of a combustion engine is given. The problem is how to make use of the model as well as the diagnostic tool RODON for combustion engine diagnosis. To solve this, the Simulink model is translated into a RODON model. Translating a Simulink model into a RODON model requires a new library in RODON. The library developed in this thesis is called AdvancedBlocks library.</p><p>The Simulink model describes the nominal behaviour of a combustion engine but for diagnosis with RODON, fault models are needed as well. Several types of faults that can occur in an engine have been studied and fault models have been implemented in RODON. The conclusion is that diagnosis in RODON with a translated engine model is possible.</p>

The goal of this thesis is to find provably correct methods for detecting conflicts between XACML rules. A conflict occurs when one rule permits a request and another denies that same request. As XACML deals with access control, we can help prevent unwanted access by verifying that it contains rules that do not have unintended conflicts. In order to help with this, we propose an algorithm to find these conflicts then use the Coq Proof Assistant to prove correctness of this algorithm. The algorithm takes a rule set specified in XACML and returns a list of pairs of indices denoting which rules conflict. It is then up to the policy writer to see if the conflicts are intended, or if they need modifying. Since we will prove that this algorithm is sound and complete, we can be assured that the list we obtain is complete and only contains true conflicts.

The goal of this thesis is to find provably correct methods for detecting conflicts between XACML rules. A conflict occurs when one rule permits a request and another denies that same request. As XACML deals with access control, we can help prevent unwanted access by verifying that it contains rules that do not have unintended conflicts. In order to help with this, we propose an algorithm to find these conflicts then use the Coq Proof Assistant to prove correctness of this algorithm. The algorithm takes a rule set specified in XACML and returns a list of pairs of indices denoting which rules conflict. It is then up to the policy writer to see if the conflicts are intended, or if they need modifying. Since we will prove that this algorithm is sound and complete, we can be assured that the list we obtain is complete and only contains true conflicts.

Diagnosis is the task of finding faults or malfunctioning components in a technical system, e.g a car. When doing diagnosis on cars with combustion engines, a computer program can be used. The computer program, also called diagnosis system, needs information about the car. This information could be data sheets of all the electronic components in the car. It could also be a description of how the engine behaves in a nominal and a non-nominal case. This information is contained in a model of the engine. RODON, a diagnostic tool developed by Sörman Information and Media AB, uses models of systems for conflict detection diagnosis. RODON needs fault models of the components to do diagnosis. The diagnosis system is then used in workshops, factories, or other places where cars need to be surveyed. In this thesis, a Simulink model of the nominal behaviour of a combustion engine is given. The problem is how to make use of the model as well as the diagnostic tool RODON for combustion engine diagnosis. To solve this, the Simulink model is translated into a RODON model. Translating a Simulink model into a RODON model requires a new library in RODON. The library developed in this thesis is called AdvancedBlocks library. The Simulink model describes the nominal behaviour of a combustion engine but for diagnosis with RODON, fault models are needed as well. Several types of faults that can occur in an engine have been studied and fault models have been implemented in RODON. The conclusion is that diagnosis in RODON with a translated engine model is possible.

The goal of this thesis is to find provably correct methods for detecting conflicts between XACML rules. A conflict occurs when one rule permits a request and another denies that same request. As XACML deals with access control, we can help prevent unwanted access by verifying that it contains rules that do not have unintended conflicts. In order to help with this, we propose an algorithm to find these conflicts then use the Coq Proof Assistant to prove correctness of this algorithm. The algorithm takes a rule set specified in XACML and returns a list of pairs of indices denoting which rules conflict. It is then up to the policy writer to see if the conflicts are intended, or if they need modifying. Since we will prove that this algorithm is sound and complete, we can be assured that the list we obtain is complete and only contains true conflicts.

Thesis (MEng)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Increasing air traffic and urbanisation has led to a cluttered airspace, particularly near airports, where both complex terrain and multiple moving obstacles are frequent. Accurately and efficiently predicting violations in safe separation criteria for commercial aircraft, a process called conflict detection, is therefore crucial in assessing risk associated with threats of collision. Existing avoidance systems in operation such as TCAS, EGPWS and ATC exhibit shortcomings, leaving room for uncertainty and possible conflict scenarios. A single on-board system capable of minimising errors in prediction would inform conflict resolution decisions more accurately as well as support the notion of free flight, an objective of next-generation air traffic management systems. This thesis investigates the viability of a modern algorithm, probability flow, as a method of probabilistic conflict detection for commercial aircraft in airport environments. Simulation results for realistic flight scenarios are presented in comparison with a ground-truth result obtained through Monte Carlo simulation. Observations are made regarding the suitability of probability flow for real-world application. It is found that probability flow is capable of calculating a tight upper bound to the probability of conflict quickly and accurately for most conflict scenarios. However, unreasonably large overestimates on the probability of conflict are obtained when flying parallel to an obstacle conflict region. This problem could lead to a high frequency of false alerts, particularly in aborted landing scenarios and at airports operating parallel runways. It is therefore advised that further research be conducted to resolve this problem before probability flow can be reliably implemented in an airport environment. / AFRIKAANSE OPSOMMING: Toenemende lugverkeer en verstedeliking het gelei tot ‘n deurmekaar lugruim, veral naby lughawens, waar beide komplekse terrein en verskeie bewegende struikelblokke gereeld voorkom. Akkuraat en doeltreffende voorspelling van oortredings in veilige skeidingskriteria vir kommersiële vliegtuie, naamlik konflik opsporing, is dus van kardinale belang in die beoordeling van die risiko wat verband hou met dreigemente van ‘n botsing. Bestaande vermyding stelsels in werking soos TCAS, EGPWS en ATC toon tekortkominge, wat ruimte laat vir onsekerheid en moontlike konflik scenario’s. ‘n Enkele aanboordstelsel, wat in staat is om foute in voorspelling te verminder, sou konflikresolusie besluite meer akkuraat in kennis stel, asook om die idee van vrye vlug te ondersteun, ‘n doelwit van toekomstige lugverkeer beheerstelsels. Hierdie tesis ondersoek die lewensvatbaarheid van ‘n moderne algoritme, waarskynlikheidsvloei, as ‘n metode van probabilistiese konflik opsporing vir kommersiële vliegtuie in die lughawens omgewing. Simulasie resultate vir realistiese vlug scenario’s word aangebied in vergelyking met ‘n grond-waarheid resultaat wat verkry word deur middel van Monte Carlo simulasie. Waarnemings word gemaak ten opsigte van die geskiktheid van waarskynlikheidsvloei vir die werklikheid. Dit is bevind dat waarskynlikheidsvloei in staat is om die berekening van ‘n stywe bogrens tot die waarskynlikheid van konflik vinnig en akkuraat te bepaal vir die meeste konflik scenario’s. Tog is daar ‘n onredelike groot oorskatting op die waarskynlikheid van konflik wat verkry word wanneer ‘n vliegtuig parallel met ‘n hindernis konflik streek vlieg. Hierdie probleem kan lei tot ‘n hoë frekwensie van valse waarskuwings, veral in mislukte landing scenario’s en by lughawens wat van parallel aanloopbane gebruik maak. Dit word dus aanbeveel dat verdere navorsing gedoen word om die probleem op te los voordat waarskynlikheidsvloei betroubaar in ’n lughawe omgewing geïmplementeer word.

The goal of this thesis is to find provably correct methods for detecting conflicts between XACML rules. A conflict occurs when one rule permits a request and another denies that same request. As XACML deals with access control, we can help prevent unwanted access by verifying that it contains rules that do not have unintended conflicts. In order to help with this, we propose an algorithm to find these conflicts then use the Coq Proof Assistant to prove correctness of this algorithm. The algorithm takes a rule set specified in XACML and returns a list of pairs of indices denoting which rules conflict. It is then up to the policy writer to see if the conflicts are intended, or if they need modifying. Since we will prove that this algorithm is sound and complete, we can be assured that the list we obtain is complete and only contains true conflicts.