Browsing by Subject "Repair"
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Item Contract-driven data structure repair : a novel approach for error recovery(2014-05) Nokhbeh Zaeem, Razieh; Khurshid, SarfrazSoftware systems are now pervasive throughout our world. The reliability of these systems is an urgent necessity. A large degree of research effort on increasing software reliability is dedicated to requirements, architecture, design, implementation and testing---activities that are performed before system deployment. While such approaches have become substantially more advanced, software remains buggy and failures remain expensive. We take a radically different approach to reliability from previous approaches, namely contract-driven data structure repair for runtime error recovery, where erroneous executions of deployed software are corrected on-the-fly using rich behavioral contracts. Our key insight is to transform the software contract---which gives a high level description of the expected behavior---to an efficient implementation which repairs the erroneous data structures in the program state upon an error. To improve efficiency, scalability, and effectiveness of repair, in addition to rich behavioral contracts, we leverage the current erroneous state, dynamic behavior of the program, as well as repair history and abstraction. A core technical problem our approach to repair addresses is construction of structurally complex data that satisfy desired properties. We present a novel structure generation technique based on dynamic programming---a classic optimization approach---to utilize the recursive nature of the structures. We use our technique for constraint-based testing. It provides better scalability than previous work. We applied it to test widely-used web browsers and found some known and unknown bugs. Our use of dynamic programming in structure generation opens a new future direction to tackle the scalability problem of data structure repair. This research advances our ability to develop correct programs. For programs that already have contracts, error recovery using our approach can come at a low cost. The same contracts can be used for systematically testing code before deployment using existing as well as our new techniques. Thus, we enable a novel unification of software verification and error recovery.Item Durability of calcium-aluminate based binders for rapid repair applications(2016-05) Lute, Racheal Dawn; Folliard, Kevin J.; Thomas, Michael D.A.; Fowler, David W; Juenger, Maria C.G.; Wheat, Harovel G.Within the last few decades, the amount of vehicle miles traveled within the US has increased approximately 40% with the construction of new roads only increasing 4% during this same time period. This dramatic increase in traffic on existing infrastructure has led to the rapid decline of the condition our nation’s roads resulting in the increased need for maintenance and repair. Rapid hardening repair materials are in high demand for these applications as they allow for minimal traffic delays and road closures. Calcium aluminate cement (CAC) is a rapid hardening binder that is used for specialty applications where high early strength and increased durability are desired. In recent years, blended cement systems incorporating both CAC and calcium sulfate (C$) with portland cement (PC) have been developed to utilize the rapid hardening characteristics of CAC but at a reduced cost. While the durability of CAC is well researched and documented, the durability of these new blended systems is not yet fully understood. The focus of this research was to evaluate the performance and long term durability of various blended systems which utilize CAC or calcium sulfoaluminate cement (CSA) to attain rapid hardening. More specifically, these systems were evaluated to determine their resistance to common modes of concrete deterioration such as alkali-silica reaction, external sulfate attack, delayed ettringite formation, carbonation, and corrosion in marine environments through in-situ lab methods and large scale outdoor exposure. The results of the testing conducted related to alkali-silica reaction, external sulfate attack, and delayed ettringite formation identified the potential for large levels of expansion in blended systems of PC:CAC:C$ and PC:CSA. Details regarding each mode of deterioration and mechanisms of expansion are discussed.Item MuAlloy : an automated mutation system for alloy(2015-05) Wang, Kaiyuan; Khurshid, Sarfraz; Perry, Dewayne E.Mutation is a powerful technique that researchers have studied for several decades in the context of imperative code. For example, mutation testing is commonly considered a '"gold standard"' for test suite quality. Mutation in the context of declarative languages is a less studied problem. This thesis introduces a foundation for mutation-driven analyses for Alloy, a first-order, declarative language based on relations. Specifically, we introduce a family of mutation operators for Alloy models and define algorithms for applying the operators on different parts of the models. We embody these operators and algorithms in our prototype tool MuAlloy that provides a GUI-based front-end for customizing the application of mutation operators. To demonstrate the potential of our approach, we illustrate the use of MuAlloy in two application scenarios: (1) mutation testing for Alloy (in the spirit of traditional mutation testing for imperative languages); and (2) program repair for Alloy using mutation.Item Repair versus replace, a second look : the windows of the tower at the University of Texas at Austin(2010-05) Freeman, Emily Paige, 1984-; Gale, Frances; Holleran, MichaelThe Secretary of the Interior’s Standards for the Treatment of Historic Buildings promote repair rather than replacement of deteriorated features when possible. Though replacement and retrofitted elements may provide improved energy efficiency with a minor impact on appearance, there is currently no guide for objectively considering the potential benefits of such treatments for historic buildings. In an effort to provide decision-making tools to those seeking to balance both preservation and economic/ sustainability concerns, this thesis will present an approach to weighing treatment options specifically for windows, including modifications for energy efficiency that are not specifically endorsed by the Secretary of the Interior’s Standards. This thesis explores the critical decision processes involved in selecting to repair or replace deteriorated historic windows, and examines those of the Main Building Tower of the University of Texas as a case study. The steel windows of the Tower, which was completed in 1937, suffer from corrosion and are not performing optimally in terms of energy efficiency. An understanding of the history and significance of the building, the current condition and performance of the windows, balanced against project-specific goals and an evaluation of current treatment options for historic windows helped narrow the potential options for the Tower. Including a “decision tree” that assists users in selecting an appropriate treatment, this thesis maps the considerations necessary to arrive at an informed solution, which may be applied to other projects with varying existing conditions and project objectives.