Computer Engineering / Bilgisayar Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/10
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Article Citation - WoS: 58Citation - Scopus: 72A Reference Model for Bim Capability Assessments(Elsevier Ltd., 2019) Yılmaz, Gökçen; Akçamete, Aslı; Demirörs, OnurVarious BIM capability and maturity models have been developed to assist architecture, engineering, construction and facilities management (AEC/FM) organizations in measuring the performance of their BIM utilizations. Due to differences in applicability and focus of these models, they are able to meet the demands of different BIM users. In this study, eight BIM capability and maturity models identified in the literature are compared based on several different criteria. The results show that there is no holistic model that includes process definitions that cover the facility life-cycle and contains measures for assessing all of these AEC/FM processes. A reference model for assessing BIM capability of AEC/FM processes was developed. It was grounded on the meta-model of ISO/IEC 330xx family of standards and developed iteratively via expert reviews and an exploratory case study. It includes AEC/FM processes which were evaluated using the BIM capability levels, their associated BIM attributes, and a four-point rating scale. BIM-CAREM was evaluated by conducting four explanatory case studies. The results showed that BIM-CAREM was capable of identifying BIM capabilities of different AEC/FM processes.Article Citation - WoS: 67Citation - Scopus: 91A Survey on Modeling and Model-Driven Engineering Practices in the Embedded Software Industry(Elsevier Ltd., 2018) Akdur, Deniz; Garousi, Vahid; Demirörs, OnurSoftware-intensive embedded systems have become an essential aspect of our lives. To cope with its growing complexity, modeling and model-driven engineering (MDE) are widely used for analysis, design, implementation, and testing of these systems. Since a large variety of software modeling practices is used in the domain of embedded software, it is important to understand and characterize the-state-of-the-practices and also the benefits, challenges and consequences of using software modeling approaches in this domain. The goal of this study is to investigate those practices in the embedded software engineering projects by identifying to what degree, why and how software modeling and MDE are used. To achieve this objective, we designed and conducted an online survey. Opinions of 627 practicing embedded software engineers from 27 different countries are included in the survey. The survey results reveal important and interesting findings about the state of software modeling and MDE practices in the worldwide embedded software industry. Among the results: (1) Different modeling approaches (from informal sketches to formalized models) are widely used in the embedded software industry with different needs and all of the usages could be effective depending on the various modeling characteristics; (2) The majority of participants use UML; and the second most frequently selected response is “Sketch/No formal modeling language” which shows the wide-spread informal usage of modeling; (3) In model-driven approaches, it is not so important to have a graphical syntax to represent the model (as in UML) and depending on the type of target embedded industrial sector, modeling stakeholders prefer models, which can be represented in a format that is readable by a machine (as in DSL); (4) Sequence diagrams and state-machines are the two most popular diagram types; (5) Top motivations for adopting MDE are: cost savings, achieving shorter development time, reusability and quality improvement. The survey results will shed light on the state of software modeling and MDE practices and provide practical benefits to embedded software professionalsArticle Citation - WoS: 16Citation - Scopus: 26Application of a Software Agility Assessment Model – Agilitymod in the Field(Elsevier Ltd., 2019) Özcan Top, Özden; Demirörs, OnurAdoption of agile values and principles and transformation of organizations towards agility are not easy and straightforward. Misinterpretation of agile principles and values, and adoption of partial solutions with few agile practices instead of holistic approaches prevent organizations to obtain full benefits of agile methods. We developed the Software Agility Assessment Reference Model (AgilityMod) for the appraisal of software projects from agility perspective and to provide guidance on specifying gaps on the road towards agility (agile maturity). The meta-model of AgilityMod was defined in relation with the ISO/IEC 15504-Process Assessment Model. AgilityMod was developed in an iterative and incremental manner by running successive case studies and getting opinions of experts for the evaluation and improvement of the Model. The multiple case study that we present here in detail included the implementation of the Model in eight software development companies. The results of this case study were evaluated by the case study participants. According to the significant majority of the case study participants, AgilityMod achieves its purpose.Article Citation - WoS: 33Citation - Scopus: 46A Semi-Automated Approach for Generating Natural Language Requirements Documents Based on Business Process Models(Elsevier Ltd., 2018) Aysolmaz, Banu; Leopold, Henrik; Reijers, Hajo A.; Demirörs, OnurContext: The analysis of requirements for business-related software systems is often supported by using business process models. However, the final requirements are typically still specified in natural language. This means that the knowledge captured in process models must be consistently transferred to the specified requirements. Possible inconsistencies between process models and requirements represent a serious threat for the successful development of the software system and may require the repetition of process analysis activities. Objective: The objective of this paper is to address the problem of inconsistency between process models and natural language requirements in the context of software development. Method: We define a semi-automated approach that consists of a process model-based procedure for capturing execution-related data in requirements models and an algorithm that takes these models as input for generating natural language requirements. We evaluated our approach in the context of a multiple case study with three organizations and a total of 13 software development projects. Results: We found that our approach can successfully generate well-readable requirements, which do not only positively contribute to consistency, but also to the completeness and maintainability of requirements. The practical use of our approach to identify a suitable subcontractor on the market in 11 of the 13 projects further highlights the practical value of our approach. Conclusion: Our approach provides a structured way to obtain high-quality requirements documents from process models and to maintain textual and visual representations of requirements in a consistent way.Article Citation - WoS: 66Citation - Scopus: 85Factors Influencing the Understandability of Process Models: a Systematic Literature Review(Elsevier Ltd., 2018) Dikici, Ahmet; Türetken, Oktay; Demirörs, OnurContext Process models are key in facilitating communication in organizations and in designing process-aware information systems. Organizations are facing increasingly larger and more complex processes, which pose difficulties to the understandability of process models. The literature reports several factors that are considered to influence the understandability of process models. However, these studies typically focus on testing of a limited set of factors. A work that collects, abstracts and synthesizes an in-depth summary of the current literature will help in developing the research in this field. Objective We conducted a systematic literature review (SLR) focusing on the empirical studies in the existing literature in order to better understand the state of the research on process model understandability, and identify the gaps and opportunities for future research. Method We searched the studies between the years 1995 and 2015 in established electronic libraries. Out of 1066 publications retrieved initially, we selected 45 publications for thorough analysis. We identified, analyzed and categorized factors that are considered to influence the understandability of process models as studied in the literature using empirical methods. We also analyzed the indicators that are used to quantify process model understandability. Results Our analysis identifies several gaps in the field, as well as issues of inconsistent findings regarding the effect of some factors, unbalanced emphasis on certain indicators, and methodological concerns. Conclusions The existing research calls for comprehensive empirical studies to contribute to a better understanding of the factors of process model understandability. Our study is a comprehensive source for researchers working on the understandability of process models and related fields, and a useful guide for practitioners aiming to generate understandable process models.Conference Object Citation - WoS: 7Citation - Scopus: 20Vertical Pattern Mining Algorithm for Multiple Support Thresholds(Elsevier Ltd., 2017) Darrab, Sadeq; Ergenç Bostanoğlu, Belgin; Ergenç, BelginFrequent pattern mining is an important task in discovering hidden items that co-occur (itemset) more than a predefined threshold in a database. Mining frequent itemsets has drawn attention although rarely occurring ones might have more interesting insights. In existing studies, to find these interesting patterns (rare itemsets), user defined single threshold should be set low enough but this results in generation of huge amount of redundant itemsets. We present Multiple Item Support-eclat; MIS-eclat algorithm, to mine frequent patterns including rare itemsets under multiple support thresholds (MIS) by utilizing a vertical representation of data. We compare MIS-eclat to our previous tree based algorithm, MISFP-growth28 and another recent algorithm, CFP-growth++22 in terms of execution time, memory usage and scalability on both sparse and dense databases. Experimental results reveal that MIS-eclat and MISFP-growth outperform CFP-growth++ in terms of execution time, memory usage and scalability.Article Citation - WoS: 11Citation - Scopus: 15A Simplified Two-View Geometry Based External Calibration Method for Omnidirectional and Ptz Camera Pairs(Elsevier Ltd., 2016) Baştanlar, YalınThe external calibration of a camera system is essential for most of the applications that involve an omnidirectional and a pan-tilt-zoom (PTZ) camera. The methods in the literature fall into two major categories; (1) a complete external calibration of the system which allows all degrees of freedom but highly time consuming, (2) spatial mapping between the pixel coordinates in omnidirectional camera and pan/tilt angles of the PTZ camera instead of explicitly computing the rotation and translation. Most methods in this category make restrictive assumptions about the camera setup such as optical axes of the cameras coincide. We propose an external calibration method that is effective and practical. Using the two-view geometry principles and making reasonable assumptions about the camera setup, calibration is performed with just two scene points. We extract rotation using the point correspondences in images. Locating the PTZ camera in the omnidirectional image is used to find the translation parameters and the real distance between the two scene points lets us compute the translation in correct scale. Results of the simulated and real image experiments show that our method works effectively in real world cases and its accuracy is comparable to the state-of-the-art methods.Article Citation - WoS: 53Citation - Scopus: 76Model-Based Mutation Testing-Approach and Case Studies(Elsevier Ltd., 2016) Belli, Fevzi; Budnik, Christof J.; Hollmann, Axel; Tuğlular, Tuğkan; Wong, W. EricThis paper rigorously introduces the concept of model-based mutation testing (MBMT) and positions it in the landscape of mutation testing. Two elementary mutation operators, insertion and omission, are exemplarily applied to a hierarchy of graph-based models of increasing expressive power including directed graphs, event sequence graphs, finite-state machines and statecharts. Test cases generated based on the mutated models (mutants) are used to determine not only whether each mutant can be killed but also whether there are any faults in the corresponding system under consideration (SUC) developed based on the original model. Novelties of our approach are: (1) evaluation of the fault detection capability (in terms of revealing faults in the SUC) of test sets generated based on the mutated models, and (2) superseding of the great variety of existing mutation operators by iterations and combinations of the two proposed elementary operators. Three case studies were conducted on industrial and commercial real-life systems to demonstrate the feasibility of using the proposed MBMT approach in detecting faults in SUC, and to analyze its characteristic features. Our experimental data suggest that test sets generated based on the mutated models created by insertion operators are more effective in revealing faults in SUC than those generated by omission operators. Worth noting is that test sets following the MBMT approach were able to detect faults in the systems that were tested by manufacturers and independent testing organizations before they were released. © 2016 Elsevier B.V.Conference Object Citation - Scopus: 4A Model of Distributed Key Generation for Industrial Control Systems(Elsevier Ltd., 2012) Kılınç, Görkem; Fovino, Igor Nai; Ferigato, Carlo; Koltuksuz, AhmetThe cyber-security of industrial control systems (ICS) is gaining high relevance due to the impact of industrial system failures on the citizen life. There is an urgent need for the consideration of security in their design, and for the analysis of the related vulnerabilities and potential threats. The high exposure of industrial critical infrastructure to cyber-threats is mainly due to the intrinsic weakness of the communication protocols used to control the process network. The peculiarities of the industrial protocols (low computational power, large geographical distribution, near to real-time constraints) make hard the effective use of traditional cryptographic schemes and in particular the implementation of an effective key management infrastructure supporting a cryptographic layer. In this paper, we describe a "model of distributed key generation for industrial control systems" we have recently implemented. The model is based on a known Distributed Key Generator protocol we have adapted to an industrial control system environment and to the related communication protocol (Modbus). To validate in a formal way selected security properties of the model, we introduced a Petri Nets representation. This representation allows for modeling attacks against the protocol and understanding some potential weaknesses of its implementation in the industrial control system environment.Article Citation - Scopus: 9Challenges for the Security Analysis of Next Generation Networks(Elsevier Ltd., 2011) Atay, Serap; Masera, MarceloThe increasing complexity of information and telecommunications systems and networks is reaching a level beyond human ability, mainly from the security assessment viewpoint. Methodologies currently proposed for managing and assuring security requirements fall short of industrial and societal expectations. The statistics about vulnerabilities and attacks show that the security, reliability and availability objectives are not reached and that the general threat situation is getting worse. With the deployment of Next Generation Networks e NGNs, the complexity of networks, considering their architecture, speed and amount of connections, will increase exponentially. There are several proposals for the network and security architectures of NGNs, but current vulnerability, threat and risk analysis methods do not appear adequate to evaluate them. Appropriate analysis methods should have some additional new characteristics, mainly regarding their adaptation to the continuous evolution of the NGNs. In addition, the application of security countermeasures will require technological improvements, which will demand further security analyses. This paper evaluates the current vulnerability, threat and risk analysis methods from the point of view of the new security requirements of NGNs. Then, the paper proposes to use autonomic and self-adaptive systems/applications for assuring the security of NGNs.