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The purpose of this paper is to provide a feature‐based characterization of version control systems (VCSs), providing an overview about the state‐of‐the‐art of versioning systems dedicated to modeling artifacts.

Based on a literature study of existing approaches, a description of the features of versioning systems is established. Special focus is set on three‐way merging which is an integral component of optimistic versioning. This characterization is employed on current model versioning systems, which allows the derivation of challenges in this research area.

The results of the evaluation show that several challenges need to be addressed in future developments of VCSs and merging tools in order to allow the parallel development of model artifacts.

Making model‐driven engineering (MDE) a success requires supporting the parallel development of model artifacts as is done nowadays for text‐based artifacts. Therefore, model versioning capabilities are a must for leveraging MDE in practice.

The paper gives a comprehensive overview of collaboration features of VCSs for software engineering artifacts in general, discusses the state‐of‐the‐art of systems for model artifacts, and finally, lists urgent challenges, which have to be considered in future model versioning system for realizing MDE in practice.

The purpose of this paper is to develop a knowledge‐based decision support tool used for assisting en‐route air traffic controllers by generating resolutions for dual aircraft conflicts after being integrated into a model‐based conflict detection and conflict resolution system.

Air traffic controller knowledge, which was obtained from the literature research, about solving aircraft conflicts is represented in a decision tree. Then it is written in Visual Basic programming language. With reference to several rules form the expert air traffic controller knowledge and some factors which affect controller conflict resolution process, the tool generates advisories consisting of eight kinds of separation strategies.

The paper finds that it is expected to increase the safety of air traffic system by supporting air traffic controller in conflict resolution process. Controller workload can be reduced by fast, reliable and acceptable resolution advisories of the tool.

The accuracy of decision tree is limited with the adequacy and quality of knowledge obtained from references, several assumptions and interpretation. Because of the unavailability of a model‐based conflict detection and resolution tool, the tool could not be evaluated in simulations.

After being integrated into a model‐based decision support tool, it can reduce the deficiencies of the model‐based tool such as low degree of resolution acceptance by controllers and low‐resolution speed by providing expert air traffic controller knowledge to the tool.

The purpose of this paper is to present and test a methodology, extending the concept of hierarchical Petri nets, to discover conflicts in a distribution channel.

The approach involves linking different levels of the supply chain and detecting conflicts occurring when the single entities, each optimized for its own operations, are combined together in a supply chain. Specifically, a methodology is proposed for synthesizing individual Petri Net models combined with matrix equations in order to detect and manage conflicts in a supply chain. These conflicts may stem from differing goals, planning and resources.

The methodology offers the user the ability to investigate the potential for conflicts in the system and manage the system to avoid such conflicts before they occur. The proposed approach holds promise for both the short term and long term for effective supply chain management and design. This would enable the supply chain to put sufficient protection (e.g. buffers) in strategic locations relative to the potential conflict or contingency plans in place to handle the conflict when it occurs.

While the ability to discover and pre‐empt conflicts would be a valuable asset to the management and design of supply chains, there is little insight found, to date, in the research on effective methods to realize detection. The current paper provides a systematic approach through the development of a hierarchical Petri net extension to detect conflicts prior to occurrence in an integrated supply chain system.

This paper aims to describe the advancements of the activities that have been carried out, in the Cost-Optimized Avionics SysTem (COAST) project, to complete the design and in-flight demonstration of the Tactical Separation System (TSS), which is an automatic support system to the pilot’s decision-making, onboard on small air transport (SAT) vehicles under single pilot operations, in the separation management.

In the framework of the Clean Sky 2 funded project COAST, some enabling technologies for single pilot operations in the EASA CS-23 category vehicles are designed and demonstrated in flight. Among the relevant flight management technologies addressed in the project, the specific one devoted to the real-time support to pilot’s decision-making in maintaining the vehicle self-separation is the TSS, designed by the Italian Aerospace Research Centre.

The TSS design started in the year 2016 and has been completed in the year 2021 after successful in-flight demonstration in the dedicated flight test campaign. The system has been validated by means of several simulation campaigns and finally demonstrated its effectiveness in providing its intended functionalities (situational awareness, conflict detection, conflict resolution) to the pilot in real flight trials, involving the presence of real conflicting aircraft.

The TSS contributes enabling the implementation of single pilot operations in CS-23 category vehicles, thanks to the possibility to support the pilot with provision of consolidated traffic picture, detection of conflicting surrounding traffic and suggestion of suitable conflict resolution manoeuvre real-time during the flight, through dedicated human–machine interface designed on purpose. The TSS supports the new separation modes that are envisaged in the future SESAR ATM target concept, with particular reference to the possible delegation of the separation responsibility to the pilot.

The purpose of the paper is to provide a two‐tier framework for managing semantic‐aware distributed firewall policies to be applied to the devices existing in one administrative domain.

Special attention is paid to the CIM‐based information model defined as the ontology to be used in this framework and the AI‐based reasoning mechanisms and components used to perform the conflict discovery tasks over the distributed firewall policies.

Mechanisms presented allow the solving some of the current issues of the network‐centric security model being used in the Internet. The two‐tier framework designed provides semantic‐aware mechanisms to perform conflict detection and automatic enforcement of policy rules in the distributed firewall scenario. This framework is based on the use of a standard information model and a semantic‐aware policy language to formally define (and then process) firewall policies.

Ongoing work is focused on identifying all kind of conflicts and anomalies that may exist in firewall systems; in parallel to this task a semi‐automatic resolver of conflicting policies is currently under design.

Network and security administrators can specify firewall policies and validate them to find syntactic and semantic errors (i.e. policy conflicts). A framework for automated validation and distribution of policies at different levels is included. This ensures that firewall policies produce the desired effects, facilitating the creation and maintenance of firewall rules in one administrative domain.

A practical and novel two‐tier system that provides detection of conflicts in rules existing in a distributed firewall scenario and the automatic and secure deployment of these rules. A packet‐filtering model, which is simple and powerful enough for the conflict discovery and rule analysis processes, has been proposed. Moreover, ontology and rule reasoning are being proposed as techniques for the conflict detection problem in this particular scenario.

Construction industrialization is emerging in the construction industry, as a result, buildings with prefabricated assemblies are gaining more and more ground. In most situations, the prefabricated building assemblies are installed by labor crews manually. If some assemblies are ill-designed, clashes between labor crews’ workspaces and them may occur, which will have bad effect on workers’ productivity and even incur hazard. The purpose of this paper is to provide a 4D building information modeling (BIM) based approach to find potential workspace conflicts during the installation process of prefabricated building assemblies in the detailed design process so as to eliminate them in advance.

First, a workspace modeling method is provided; second, three kinds of workspace conflicts are analyzed; third, a 4D-BIM-based approach is established; fourth, a prototype tool based on the approach is developed; and finally, a case study is conducted to test the tool.

The result shows that the proposed tool can detect or precaution workspace conflicts and visualize them in a series of views; in doing so, valuable information can be obtained for improving the design quality of prefabricated assemblies.

The proposed approach and tool only concern the congestions caused by ill-designed prefabricated components; the tool needed to be further optimized for speed; the tests on the tool are limited to a single case study; and more tests are needed to verify its effectiveness.

This research provides a 4D-BIM-based approach and a prototype tool for installation workspace analysis. It can be used to provide support for design optimization of prefabricated building assemblies.

Conceptual design is important in that it determines the creativity of products, which is key to the competition of the product market and the function and cost of product are mainly determined in this phase. At the same time it is complex in that it involves the consideration of many different fields in the whole design process. Studying some computer supported cooperative techniques to support effective conceptual design activity is absolutely necessary. This paper presents the models and tools of computer supported cooperative conceptual design (CSCCD) which includes an auto‐resolving model, a human‐human interaction model, automatic cooperation tools and interactive cooperation tools. Experiments have been carried out in the conceptual design of a motorcycle to put the above theories into application.

The spatial conflicts and congestion of construction resources are challenges that lead to the reduction in efficiency. The purpose of this paper is to enable users to detect and resolve workspace conflicts by implementing four resolution strategies in a five-dimensional (5D) CAD model. In addition to resolving conflicts, the model should be able to optimize time and cost of the projects. In other words, three variables of spatial conflicts, time and cost of project are considered simultaneously in the proposed model to find the optimum solution.

In the first step, a 5D simulation model is developed that includes time, cost and geometrical information of a project. Then, time-cost trade-off analysis was carried out to distinguish optimum schedule. The schedule was imported to the 5D CAD model to detect spatial conflicts. Finally, a novel algorithm was implemented to solve identified conflicts while imposing minimum project’s time and cost. Several iterations are performed to resolve all clashes using conflict resolution algorithm and visual simulation model.

The proposed methodology in this research was applied to a real case. Results showed that in comparison to the normal and initial schedule with 19 conflicts, the finalized schedule has no conflict, while time and cost of the project are both reduced.

Implementing the proposed methodology in construction projects requires proper technical basis in this field. In this regard, the executive user should have a proper understanding of the principles, concepts and tools of building information modeling and have project management knowledge. Also, the implementation conditions of the basic model requires the determination of the construction methods, estimated volumes of working items, scheduling and technical specification. The designed methodology also has two limitations regarding to its implementation. The first is the fact that strategies should be applied manually to the schedule. The other one pertains to the number of strategies used in the research. Four strategies have been used in the conflict resolution algorithm directly and the two others (spatial divisibility and activities breakdown strategies) have been used as default strategies in the visual simulation model. Since the unused strategies including the changing of construction method and the activity resources are subjective and depend upon the planner and project manager’s personal opinion, the authors have avoided using them in this research.

The method proposed in this research contributes the coordination of the working teams at the planning and execution phases of the project. In fact, the best location and work direction for each working team is presented as a schedule, so that the space conflict may not come about and the cost can be minimized. This visual simulation not only deepens the planners’ views about the executive barriers and the spatial conditions of the worksite, it also makes the construction engineers familiar on a daily basis with their executive scope. Therefore, it considerably improves the interactions and communication of the planning and construction teams. Another advantage and application of this methodology is the use of initial and available projects’ documents including the schedule and two-dimensional drawings. The integration of these basic documents in this methodology helps identify the spatial conflicts efficiently. To achieve this, the use of the existing and widely-used construction tools has facilitated the implementation of the methodology. Using this system, planners have applied the strategies in an order of priority and can observe the results of each strategy visually and numerically in terms of time, cost and conflicts. This methodology by providing the effective resolution strategies guides the practitioner to remove conflicts while optimum time and cost are imposed to project.

Contrary to the previous models that ignore cost, the proposed model is a 5D visual simulation model, which considers the variable of cost as a main factor for conflict identification and resolution. Moreover, a forward-pass approach is introduced to implement resolution strategies that are novel compared to other investigations.

Pervasive computing environments such as a pervasive campus domain, shopping, etc. will become commonplaces in the near future. The key to enhance these system environments with services relies on the ability to effectively model and represent contextual information, as well as spontaneity in downloading and executing the service interface on a mobile device. The system needs to provide an infrastructure that handles the interaction between a client device that requests a service and a server which responds to the client's request via Web service calls. The system should relieve end‐users from low‐level tasks of matching services with locations or other context information. The mobile users do not need to know or have any knowledge of where the service resides, how to call a service, what the service API detail is and how to execute a service once downloaded. All these low‐level tasks can be handled implicitly by a system. The aim of this paper is to investigate the notion of context‐aware regulated services, and how they should be designed, and implemented.

The paper presents a detailed design, and prototype implementation of the system, called mobile hanging services (MHS), that provides the ability to execute mobile code (service application) on demand and control entities' behaviours in accessing services in pervasive computing environments. Extensive evaluation of this prototype is also provided.

The framework presented in this paper enables a novel contextual services infrastructure that allows services to be described at a high level of abstraction and to be regulated by contextual policies. This contextual policy governs the visibility and execution of contextual services in the environment. In addition, a range of contextual services is developed to illustrate different types of services used in the framework.

The main contribution of this paper is a high‐level model of a system for context‐aware regulated services, which consists of environments (domains and spaces), contextual software components, entities and computing devices.

This paper proposes to apply the lean philosophy principle of minimizing or eliminating non-value adding activities combined with 4D building information modeling (BIM) simulations to reduce transportation waste in construction production processes.

This study adopts design science research (DSR) because of its prescriptive character to produce innovative constructions (artifacts) to solve real-world problems. The artifact proposed is a set of constructs for evaluating the utility of 4D BIM simulations for transportation waste reduction. The authors performed two learning cycles using empirical studies in projects A, B and C. The construction process of cast-in-place (CIP) reinforcement concrete (RC) was selected to demonstrate and evaluate 4D BIM's utility. The empirical studies focused on understanding the current transportation waste, collecting actual performance data during job site visits and demonstrating the usage of 4D BIM.

In the first cycle, 4D BIM successfully allowed users to understand the CIP-RC process's transportation activities, which were modeled. In the second cycle, 4D BIM enabled better decision-making processes concerning the definitions of strategies for placing reusable formworks for CIP concrete walls by planning transportation activities.

In Cycle 2, three different scenarios were simulated to identify the most suitable formwork assembly planning, and the results were compared to the real situations identified during the job site visits. The scenario chosen demonstrated that the 4D BIM simulation yielded an 18.75% cycle time reduction. In addition, the simulation contributed to a decrease in transportation waste that was previously identified.

The original contribution of this paper is the use of 4D BIM simulation for managing non-value adding activities to reduce transportation waste. The utility of 4D BIM for the reduction of those conflicts considered three constructs: (1) the capacity to improve transportation activity efficiency, (2) the capacity to improve construction production efficiency and (3) the capacity to reduce transportation waste consequences.