Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Conference Object Citation - WoS: 2Citation - Scopus: 3Secure Iot Update Using Blockchain(IEEE, 2021) Kaptan, Melike; Tomur, Emrah; Ayav, Tolga; Erten, Yusuf MuratIn this study a platform is devised to send automatic remote updates for embedded devices. In this scenario there are Original Equipment Manufacturers (OEMs), Software suppliers, blockchain nodes, Gateways and embedded devices. OEMs and software suppliers are there to keep their software on Inter Planetary File System (IPFS) and send the meta-data and hashes of their software to the blockchain nodes in order to keep this information distributed and ready to be requested and used. There are also gateways which are the members of the blockchain and the IPFS network. Gateways are responsible for asking for a specific update for specific devices from IPFS database using the meta-data kept on the blockchain, and they will send those hashed secure updates to the devices. In order to provide a traceable data keeping platform, gateway update operations are handled as transactions in a second blockchain network which is the clockchain of the gateways. The system was implemented as of the two separate blockchain networks and it has been shown that, despite the calculation overhead of the member devices, by separating the functions between the two blockchain networks a more reliable and secure platform can be achieved.Conference Object Citation - WoS: 12Citation - Scopus: 20Loyalty Program Using Blockchain(IEEE, 2020) Sönmeztürk, Osman; Ayav, Tolga; Erten, Yusuf MuratThe traditional loyalty systems usually offer people benefits in a specific sector. The users usually need to stay within the loyalty system for a long time and accumulate points in order to win rewards which may not be very interesting for them most of the time. Additionally, users usually do not prefer to share their personal information to join these loyalty systems due to privacy concerns. It has, therefore, been observed that the number of customers in the loyalty systems is decreasing day by day. To reduce these drawbacks a loyalty program which complies with ERC20 standards was proposed in this study using tokens based on the Ethereum blockchain. Using this new generation loyalty system, users can convert their earned tokens to Ether in the market and they can receive services or products with the accumulated tokens according to their interests from any supplier that has been contracted by the manufacturer. Additionally, users in the designed system do not need to carry many different cards, it is adequate to have only one Ethereum wallet. Furthermore, users do not need to share any personal data to join the loyalty system. Suppliers can also request Ether from the manufacturer for the tokens they have accumulated from the members of the loyalty system. The proposed loyalty system has been implemented and presented in this study.Article Citation - WoS: 15Citation - Scopus: 18Achieving Query Performance in the Cloud Via a Cost-Effective Data Replication Strategy(Springer, 2021) Tos, Uras; Mokadem, Riad; Hameurlain, Abdelkader; Ayav, TolgaMeeting performance expectations of tenants without sacrificing economic benefit is a tough challenge for cloud providers. We propose a data replication strategy to simultaneously satisfy both the performance and provider profit. Response time of database queries is estimated with the consideration of parallel execution. If the estimated response time is not acceptable, bottlenecks are identified in the query plan. Data replication is realized to resolve the bottlenecks. Data placement is heuristically performed in a way to satisfy query response times at a minimal cost for the provider. We demonstrate the validity of our strategy in a performance evaluation study.Article Citation - WoS: 9Citation - Scopus: 11Test Input Generation From Cause-Effect Graphs(Springer, 2021) Kavzak Ufuktepe, Deniz; Ayav, Tolga; Belli, FevziCause-effect graphing is a well-known requirement-based and systematic testing method with a heuristic approach. Since it was introduced by Myers in 1979, there have not been any sufficiently comprehensive studies to generate test inputs from these graphs. However, there exist several methods for test input generation from Boolean expressions. Cause-effect graphs can be more convenient for a wide variety of users compared to Boolean expressions. Moreover, they can be used to enforce common constraints and rules on the system variables of different expressions of the system. This study proposes a new mutant-based test input generation method, Spectral Testing for Boolean specification models based on spectral analysis of Boolean expressions using mutations of the original expression. Unlike Myers' method, Spectral Testing is an algorithmic and deterministic method, in which we model the possible faults systematically. Furthermore, the conversion of cause-effect graphs between Boolean expressions is explored so that the existing test input generation methods for Boolean expressions can be exploited for cause-effect graphing. A software is developed as an open-source extendable tool for generating test inputs from cause-effect graphs by using different methods and performing mutation analysis for quantitative evaluation on these methods for further analysis and comparison. Selected methods, MI, MAX-A, MUTP, MNFP, CUTPNFP, MUMCUT, Unique MC/DC, and Masking MC/DC are implemented together with Myers' technique and the proposed Spectral Testing in the developed tool. For mutation testing, 9 common fault types of Boolean expressions are modeled, implemented, and generated in the tool. An XML-based standard on top of GraphML representing a cause-effect graph is proposed and is used as the input type to the approach. An empirical study is performed by a case study on 5 different systems with various requirements, including the benchmark set from the TCAS-II system. Our results show that the proposed XML-based cause-effect graph model can be used to represent system requirements. The developed tool can be used for test input generation from proposed cause-effect graph models and can perform mutation analysis to distinguish between the methods with respect to the effectiveness of test inputs and their mutant kill scores. The proposed Spectral Testing method outperforms the state-of-the-art methods in the context of critical systems, regarding both the effectiveness and mutant kill scores of the generated test inputs, and increasing the chances of revealing faults in the system and reducing the cost of testing. Moreover, the proposed method can be used as a separate or complementary method to other well-performing test input generation methods for covering specific fault types.Article Citation - WoS: 2Citation - Scopus: 1Mutant Selection by Using Fourier Expansion(Türkiye Klinikleri Journal of Medical Sciences, 2020) Takan, Savaş; Ayav, TolgaMutation analysis is a widely used technique to evaluate the effectiveness of test cases in both hardware and software testing. The original model is mutated systematically under certain fault assumptions and test cases are checked against the mutants created to see whether the test cases can detect the faults or not. Mutation analysis is usually a computationally intensive task, particularly in finite state machine (FSM) testing due to a possibly huge amount of mutants. Random selection could be a practical reduction method under the assumption that each mutant is identical in terms of the probability of occurrence of its associating fault. The present study proposes a mutant selection method based on Fourier analysis of Boolean functions. Fourier helps to identify the most effective transitions on the output so that the mutants related to those transitions can be selected. Such mutants are considered more important since they are more likely to be killed. To evaluate the method, test cases are generated by the well-known W method, which has the capability of detecting every potential fault. The original and reduced sets of mutants are compared with respect to their importance values. Evaluations show that the mutants selected by the proposed technique are more effective, which reduces the cost of mutation analysis without sacrificing the performance of the mutation analysis.Conference Object Osek/vdx Uyumlu Katı Gerçek-zamanlı İşletim Sistemleri için Zamanlama Mimarilerinin Değerlendirilmesi(IEEE, 2020) Saydam, Berkay; Ayav, TolgaDeveloping technology is reflected to the vehicles as well. But it brings the challenge of adding new functionalities to vehicles without compromising safety. The chips, which are used to provide the functionalities, are determined in the first step of ECU design. This decision will effect the remaining part of the development. Designing hardware and software together with testing phase is a long process in automotive industry. Changing the design of the hardware is quite costly after an ECU begins to be used in field. For these reasons, the selection of chips is directly related to cost and the functionality which should be provided to customer. Tasks, which fulfill desired functionality, provide a balance between performance and safety. These were evaluated for an OSEK/VDX certified OS and results are presented from the scheduling algorithms point of view. © 2020 IEEE.Conference Object Yazılım Yapısal Kapsama Analizinde Testlerin Önceliklendirilmesi(CEUR Workshop Proceedings, 2015) Ayav, TolgaBu çalışma değiştirilmiş koşul/karar kapsama stratejisince türetilmiş test girişlerinin önceliklendirilmesi için bir teknik sunmaktadır. Teknik Fourier analizine dayanmaktadır ve testlerin hata ortaya çıkarma potansiyellerine göre sıralanabilmesini hedeflemektedir. Bu sayede yazılımın yüksek öncelikli testlerden başlayarak düşüğe doğru sınanması veya test kümesinin yüksek öncelikli testleri kapsayacak şekilde daraltılması mümkün olabilecektir.Conference Object Sonlu Durum Makinelerinin Fourier Analizi Tabanlı Sınanması(CEUR Workshop Proceedings, 2018) Takan, Savaş; Ayav, TolgaSonlu durum makinesi (FSM), devre ve yazılım testlerinde yaygın kullanıma sahip bir modelleme tekniğidir. FSM'lerin testi için literatürde çeşitli yöntemler bulunmakla birlikte, modellerin büyümesi sonucu test kümesinin büyüklüğü, hata yakalama oranı ve test üretim süresi gibi konularda yüksek başarıma sahip alternatif test yöntemlerine ihtiyaç bulunmaktadır. Bu çalışma ikili fonksiyonların Fourier analizine dayanan yeni bir test oluşturma yöntemi önermektedir. İlk sonuçlar, fonksiyonun frekans bileşenlerinden yararlanarak oluşturulan test takımının daha yüksek bir performansa sahip olduğunu göstermektedir. Önerilen yöntem, karakteristiği, maliyeti ve hata yakalama oranı üzerinden literatürden seçilen iki yöntemle karşılaştırılmıştır.Article Citation - WoS: 26Citation - Scopus: 30Ensuring Performance and Provider Profit Through Data Replication in Cloud Systems(Springer Verlag, 2017) Tos, Uras; Mokadem, Riad; Hameurlain, Abdelkader; Ayav, Tolga; Bora, ŞebnemCloud computing is a relatively recent computing paradigm that is often the answer for dealing with large amounts of data. Tenants expect the cloud providers to keep supplying an agreed upon quality of service, while cloud providers aim to increase profits as it is a key ingredient of any economic enterprise. In this paper, we propose a data replication strategy for cloud systems that satisfies the response time objective for executing queries while simultaneously enables the provider to return a profit from each execution. The proposed strategy estimates the response time of the queries and performs data replication in a way that the execution of any particular query is still estimated to be profitable for the provider. We show with simulations that how the proposed strategy fulfills these two criteria.Conference Object Citation - WoS: 17Citation - Scopus: 30A Performance and Profit Oriented Data Replication Strategy for Cloud Systems(Institute of Electrical and Electronics Engineers Inc., 2017) Tos, Uras; Mokadem, Riad; Hameurlain, Abdelkader; Ayav, Tolga; Bora, ŞebnemIn today's world, tenants of cloud systems expect timely responses to queries that process ever-increasing sizes of data. However, most cloud providers offer their services without any performance guarantees to their tenants. In this paper we propose a data replication strategy that aims to satisfy performance guarantees for the tenant while ensuring profitability of the cloud provider. Our strategy estimates the response time of the queries, as well as the expenditures that affect the profitability of the cloud provider. The decision of whether to perform replication is determined by the fulfillment of these two criteria. Validity of the proposed strategy is provided by means of a simulation study.
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