Providing a formal linkage between MDG and HOL based on a verified MDG system.

Formal verification techniques can be classified into two categories: deductive theorem proving and symbolic state enumeration. Each method has complementary advantages and disadvantages. In general, theorem provers are high reliability systems. They can be applied to the expressive formalisms that are capable of modelling complex designs such as processors. However, theorem provers use a glass-box approach. To complete a verification, it is necessary to understand the internal structure in detail. The learning curve is very steep and modeling and verifying a system is very time-consuming. In contrast, symbolic state enumeration tools use a black-box approach. When verifying a design, the user does not need to understand its internal structure. Their advantages are their speed and ease of use. But they can only be used to prove relatively simple designs and the system security is much lower than the theorem proving system. Many hybrid tools have been developed to reap the benefits of both theorem proving Systems and symbolic state enumeration Systems. Normally, the verification results from one system are translated to another system. In other words, there is a linkage between the two Systems. However, how can we ensure that this linkage can be trusted? How can we ensure the verification system itself is correct? The contribution of this thesis is that we have produced a methodology which can provide a formal linkage between a symbolic state enumeration system and a theorem proving system based on a verified symbolic state enumeration system. The methodology has been partly realized in two simplified versions of the MDG system (a symbolic state enumeration system) and the HOL system (a theorem proving system) which involves the following three steps. First, we have verified aspects of correctness of two simplified versions of the MDG system. We have made certain that the semantics of a program is preserved in those of its translated form. Secondly, we have provided a formal linkage between the MDG system and the HOL system based on importing theorems. The MDG verification results can be formally imported into HOL to form the HOL theorems. Thirdly, we have combined the translator correctness theorems with the importing theorems. This combination allows the low level MDG verification results to be imported into HOL in terms of the semantics of a high level language (MDG-HDL). We have also summarized a general method which is used to prove the existential theorem for the specification and implementation of the design. The feasibility of this approach has been demonstrated in a case study: the verification of the correctness and usability theorems of a vending machine

Emerging trends proceedings of the 17th International Conference on Theorem Proving in Higher Order Logics: TPHOLs 2004

technical reportThis volume constitutes the proceedings of the Emerging Trends track of the 17th International Conference on Theorem Proving in Higher Order Logics (TPHOLs 2004) held September 14-17, 2004 in Park City, Utah, USA. The TPHOLs conference covers all aspects of theorem proving in higher order logics as well as related topics in theorem proving and verification. There were 42 papers submitted to TPHOLs 2004 in the full research cate- gory, each of which was refereed by at least 3 reviewers selected by the program committee. Of these submissions, 21 were accepted for presentation at the con- ference and publication in volume 3223 of Springer?s Lecture Notes in Computer Science series. In keeping with longstanding tradition, TPHOLs 2004 also offered a venue for the presentation of work in progress, where researchers invite discussion by means of a brief introductory talk and then discuss their work at a poster session. The work-in-progress papers are held in this volume, which is published as a 2004 technical report of the School of Computing at the University of Utah

Hierarchical formal verification using a hybrid tool

We describe a hybrid formal hardware verification tool that links the HOL interactive proof system and the MDG automated hardware verification tool. It supports a hierarchical verification approach that mirrors the hierarchical structure of designs. We obtain the advantages of both verification paradigms. We illustrate its use by considering a component of a communications chip. Verification with the hybrid tool is significantly faster and more tractable than using either tool alone

Hybrid verification integrating HOL theorem proving with MDG model checking

In this paper, we describe a hybrid tool for hardware formal verification that links the HOL (higher-order logic) theorem prover and the MDG (multiway decision graphs) model checker. Our tool supports abstract datatypes and uninterpreted function symbols available in MDG, allowing the verification of high-level specifications. The hybrid tool, HOL-MDG, is based on an embedding in HOL of the grammar of the hardware modeling language, MDG-HDL, as well as an embedding of the first-order temporal logic L"m"d"g used to express properties for the MDG model checker. Verification with the hybrid tool is faster and more tractable than using either tools separately. We hence obtain the advantages of both verification paradigms

The verification of MDG algorithms in the HOL theorem prover

Formal verification of digital systems is achieved, today, using one of two main approaches: states exploration (mainly model checking and equivalence checking) or deductive reasoning (theorem proving). Indeed, the combination of the two approaches, states exploration and deductive reasoning promises to overcome the limitation and to enhance the capabilities of each. Our research is motivated by this goal. In this thesis, we provide the entire necessary infrastructure (data structure + algorithms) to define high level states exploration in the HOL theorem prover named as MDG-HOL platform. While related work has tackled the same problem by representing primitive Binary Decision Diagram (BDD) operations as inference rules added to the core of the theorem prover, we have based our approach on the Multiway Decision Graphs (MDGs). MDG generalizes ROBDD to represent and manipulate a subset of first-order logic formulae. With MDGs, a data value is represented by a single variable of an abstract type and operations on data are represented in terms of uninterpreted function. Considering MDGs instead of BDDs will raise the abstraction level of what can be verified using a state exploration within a theorem prover. The MDGs embedding is based on the logical formulation of an MDG as a Directed Formulae (DF). The DF syntax is defined as HOL built-in data types. We formalize the basic MDG operations using this syntax within HOL following a deep embedding approach. Such approach ensures the consistency of our embedding. Then, we derive the correctness proof for each MDG basic operator. Based on this platform, the MDG reachability analysis is defined in HOL as a conversion that uses the MDG theory within HOL. Then, we demonstrate the effectiveness of our platform by considering four case studies. Our obtained results show that this verification framework offers a considerable gain in terms of automation without sacrificing CPU time and memory usage compared to automatic model checker tools. Finally, we propose a reduction technique to improve MDGs model checking based on the MDG-HOL platform. The idea is to prune the transition relation of the circuits using pre-proved theorems and lemmas from the specification given at system level. We also use the consistency of the specifications to verify if the reduced model is faithful to the original one. We provide two case studies, the first one is the reduction using SAT-MDG of an Island Tunnel Controller and the second one is the MDG-HOL assume-guarantee reduction of the Look-Aside Interface. The obtained results of our approach offers a considerable gain in terms of heuristics and reduction techniques correctness as to commercial model checking; however a small penalty is paid in terms of CPU time and memory usag

Model Transformation Languages with Modular Information Hiding

Model transformations, together with models, form the principal artifacts in model-driven software development. Industrial practitioners report that transformations on larger models quickly get sufficiently large and complex themselves. To alleviate entailed maintenance efforts, this thesis presents a modularity concept with explicit interfaces, complemented by software visualization and clustering techniques. All three approaches are tailored to the specific needs of the transformation domain

Model Transformation Languages with Modular Information Hiding

Model transformations, together with models, form the principal artifacts in model-driven software development. Industrial practitioners report that transformations on larger models quickly get sufficiently large and complex themselves. To alleviate entailed maintenance efforts, this thesis presents a modularity concept with explicit interfaces, complemented by software visualization and clustering techniques. All three approaches are tailored to the specific needs of the transformation domain

Income improvement at household for community members Masama-Rundugai Ward in Hai District

This project of income improvement at household level is a result of the need assessment conducted in Masama-Rundugai ward in early 2006. Assessment indicated that low income is a root cause of the core problem of poverty. Lack of employment, lack of skills to run micro business, ignorance and poor leadership commitment are other causes contributing to the problem. Goal and objectives were set through involving stakeholders. Implementation was conducted following the assessment which indicated what strategies to undertake to achieve the intended goals. Through survey researcher identified two appropriate strategies: The first was the formation of Savings and Credit Cooperative Society (SACCOS). It was necessary for community members to form their own SACCOS close to their destinations to ease access of soft loans. This was the reason of this project in this area. The second was capacity building for community members on entrepreneurship. During project implementation entrepreneurship manual for training at community level was developed and used to train community members who have been sensitized to borrow soft loans and apply in their micro business. SACCOS steering committee developed constitution, and was one of registration requirements. District Cooperative officers were consulted for registration process. Community members were mobilized to join the SACCOS. The response was that 57 women and 46 men joined the SACCOS (MKALONGO SACCOS) in the first place. Some organization promised to provide soft loan in 2006/2007 budget through the MKALONGO SACCOS. (Author abstract)Mweta, G. A. (2007). Income improvement at household for community members Masama-Rundugai Ward in Hai District. Retrieved from http://academicarchive.snhu.eduMaster of Science (M.S.)School of Community Economic Developmen

Slicing of Concurrent Programs and its Application to Information Flow Control

This thesis presents a practical technique for information flow control for concurrent programs with threads and shared-memory communication. The technique guarantees confidentiality of information with respect to a reasonable attacker model and utilizes program dependence graphs (PDGs), a language-independent representation of information flow in a program

An evaluation of the phase-out management system of an ozone depleting substance HCFC-22 and its environmental and socioeconomic implications in Botswana

Climate change and ozone depletion are topical challenges the world over and are both attributed mainly to human activities, particularly emissions of ozone depleting substances (ODSs). One such substance is chlorodifluoromethane (HCFC-22), a cheap, widely used refrigerant with a high global warming potential of 1780. Botswana is a signatory to the Montreal Protocol (MP), which guides international efforts to phase-out HCFC-22 and requires signatories to develop and implement a country-level Hydrochlorofluorocarbon Phase-out Management Plan (HPMP). This study, which used a mixed methods approach, was conducted to evaluate the phase-out of HCFC-22 management strategies and their environmental and socioeconomic implications in Botswana. A census of nine HCFC-22 importing companies was conducted and probability sampling proportional to size was used to select a sample of 159 respondents from the Department of Meteorological Services, HCFC-22 importers, customs officers from 20 purposively selected Botswana entry ports and HCFC-22 consumers from the importing companies. Category-specific respondent questionnaires and interview guides, site visits and assessment of records were used to gather data. Of particular interest were the annual HCFC-22 importation figures for each company, the Botswana Unified Revenue Services and the National Ozone Unit, as well as the level of compliance of the companies’ HCFC-22 phase-out management practices with relevant national regulations, the Botswana HPMP and the MP resolutions. Botswana’s HCFC-22 importers were found to be moderately to highly compliant to nonregulatory elements rather than regulatory elements. Overall, HCFC-22 consumption decreased from the baseline to 10.5% for the first stage (2013-2015), which was slightly more than the 10% reduction expected. A steady decrease in HCFC-22 consumption was noted towards the 35% target for 2020, largely due to awareness-raising initiatives directed at the surveyed stakeholders. Absolute HCFC-22 consumption dropped by approximately 510400 kgs from 2011-2017 or 28072 ozone depleting potential saved. On the downside, gaps were identified in the industry-wide quota-system, data reporting, prevention of illegal ODS trade, service technician training, user knowledge of alternatives and disposal of ODS equipment. The study recommends the use of a planning, policy formulation and implementation framework that integrates and balances three fundamentals, namely, stakeholder involvement, the process and the plan enablers