A comparison of two different model checking techniques

Thesis (MSc)--University of Stellenbosch, 2003.ENGLISH ABSTRACT: Model checking is a computer-aided verification technique that is used to verify properties about the formal description of a system automatically. This technique has been applied successfully to detect subtle errors in reactive systems. Such errors are extremely difficult to detect by using traditional testing techniques. The conventional method of applying model checking is to construct a model manually either before or after the implementation of a system. Constructing such a model requires time, skill and experience. An alternative method is to derive a model from an implementation automatically. In this thesis two techniques of applying model checking to reactive systems are compared, both of which have problems as well as advantages. Two specific strategies are compared in the area of protocol development: 1. Structuring a protocol as a transition system, modelling the system, and then deriving an implementation from the model. 2. Automatically translating implementation code to a verifiable model. Structuring a reactive system as a transition system makes it possible to verify the control flow of the system at implementation level-as opposed to verifying the control flow at abstract level. The result is a closer correspondence between implementation and specification (model). At the same time testing, which is restricted to small, independent code fragments that manipulate data, is simplified significantly. The construction of a model often takes too long; therefore, verification results may no longer be applicable when they become available. To address this problem, the technique of automated model extraction was suggested. This technique aims to reduce the time required to construct a model by minimising manual input during model construction. A transition system is a low-level formalism and direct execution through interpretation is feasible. However, the overhead of interpretation is the major disadvantage of this technique. With automated model extraction there are disadvantages too. For example, differences between the implementation and specification languages-such as constructs present in the implementation language that cannot be expressed in the modelling language-make the development of an automated model extraction tool extremely difficult. In conclusion, the two techniques are compared against a set of software development considerations. Since a specific technique is not always preferable, guidelines are proposed to help select the best approach in different circumstances.AFRIKAANSE OPSOMMING: Modeltoetsing is 'n rekenaargebaseerde verifikasietegniek wat gebruik word om eienskappe rakende 'n formele spesifikasie van 'n stelsel te verifieer. Die tegniek is al suksesvol toegepas om subtiele foute in reaktiewe stelsels op te spoor. Sulke foute word uiters moeilik opgespoor as tradisionele toetsings tegnieke gebruik word. Tradisioneel word modeltoetsing toegepas deur 'n model te bou voor of na die implementasie van 'n stelsel. Om'n model te bou verg tyd, vernuf en ervaring. 'n Alternatiewe metode is om outomaties 'n model van 'n implementasie af te lei. In hierdie tesis word twee toepassingstegnieke van modeltoetsing vergelyk, waar beide tegnieke beskik oor voordele sowel as nadele. Twee strategieë word vergelyk in die gebied van protokol ontwikkeling: 1. Om 'n protokol as 'n oorgangsstelsel te struktureer, dit te moduleer en dan 'n implementasie van die model af te lei. 2. Om outomaties 'n verifieerbare model van 'n implementasie af te lei. Om 'n reaktiewe stelsel as 'n oorgangsstelsel te struktureer maak dit moontlik om die kontrolevloei op implementasie vlak te verifieer-in teenstelling met verifikasie van kontrolevloei op 'n abstrakte vlak. Die resultaat is 'n nouer band wat bestaan tussen die implementasie en die spesifikasie. Terselfdetyd word toetsing, wat beperk word tot klein, onafhanklike kodesegmente wat data manupileer, beduidend vereenvoudig. Die konstruksie van 'n model neem soms te lank; gevolglik, wanneer die verifikasieresultate beskikbaar word, is dit dalk nie meer toepaslik op die huidige weergawe van 'n implementasie nie. Om die probleem aan te spreek is 'n tegniek om modelle outomaties van implementasies af te lei, voorgestel. Die doel van die tegniek is om die tyd wat dit neem om 'n model te bou te verminder deur handtoevoer tot 'n minimum te beperk. 'n Oorgangsstelsel is 'n laevlak formalisme en direkte uitvoering deur interpretasie is wesenlik. Die oorhoofse koste van die interpreteerder is egter die grootste nadeel van die tegniek. Daar is ook nadele wat oorweeg moet word rakende die tegniek om outomaties modelle van implementasies af te lei. Byvoorbeeld, verskille tussen die implementasietaal en spesifikasietaal=-soos byvoorbleed konstrukte wat in die implementasietaal gebruik word wat nie in die modeleringstaal voorgestel kan word nie-vrnaak die ontwikkeling van 'n modelafieier uiters moeilik. As gevolg word die twee tegnieke vergelyk teen 'n stel van programatuurontwikkelingsoorwegings. Omdat 'n spesifieke tegniek nie altyd voorkeur kan geniet nie, word riglyne voorgestel om te help met die keuse om die beste tegniek te kies in verskillende omstandighede

The Role of Education in Preventing Honour-Based Abuse in England

Honour-based abuse (HBA) is a form of abuse that frequently remains undetected despite its pervasive nature and catastrophic effects. As an act of violence perpetrated predominantly against women and girls, HBA is the overarching term used for abuse inflicted upon victims because they have supposedly dishonoured their family and brought shame to their community. To date, there is a paucity of research that specifically explores the role of education in preventing HBA in England. In seeking to strengthen and advance knowledge in this area, this research aims to gain insights into the perspectives of key participants about the cross-cultural and contested nature of HBA, including the factors contributing to it, the ramifications for local and national policy, and the role of education in preventing HBA in the context of England. This thesis also illustrates how the insidious and invidious practices of HBA continue to be perpetuated toward the most vulnerable within society. Underpinned by a feminist theoretical framework, qualitative analysis was employed to explore how participants perceive how education may contribute to prevention of HBA. The research participants interviewed for this study, over a period of eight months, included four activists, three politicians, one Home Office senior civil servant, four academics, two Crown Prosecution Service (CPS) staff, and one senior police officer. The semi-structured interviews provided a comprehensive understanding of the significance and meaning that the research participants placed on the role of education in HBA, and HBA prevention. Thematic analysis was undertaken after the data was transcribed and input into NVivo to detect themes, identify codes, and define key themes and underlying subthemes. This analysis uncovered five key themes within this research inquiry. The first theme related to the definitions and practices of HBA and exploring participant perceptions of the elements that contribute to and influence HBA. The second theme identified the origins and perpetuations of HBA. In broad terms, this theme focused on the origins of the cultural practice, identified the trigger factors, and examined the impact of gender and patriarchy in relation to HBA. The third theme was in relation to identification and definition of perpetrators and victims. The fourth theme provided an overview of the positionality of the research participants including their backgrounds, roles, and responsibilities. The fifth theme explored solutions to HBA, including methods of eradication, taking into account interviewees’ views on how to address HBA, and the role of education and government organisations in preventing HBA. Whilst it was clear that steps have been taken by the State to address the phenomenon of HBA through community initiatives and statutory education, the impact of these initiatives on HBA was limited due to several factors, such as lack of effective training for teachers, community literacy in HBA, race relations within the migrant community, funding constraints, and the multiple viewpoints and experiences due to the intersectional nature of HBA. Weaving through the tapestry of migration, culture, discrimination, gender norms, and societal roles, this research generates new understandings on the role of education in preventing HBA in England by drawing on the views of key participants on policies and initiatives related to HBA