Similarity is a key property across two or more interactive systems. Indeed, interacting with similar systems can bring benefits (e.g., reduced learning efforts and training time) but may also raise issues (e.g., interference errors and higher cognitive load). Interactive systems may be similar, as they correspond to the same work and tasks performed with different underlying systems, such as the pilots’ tasks in the cockpit of an Airbus A320 and a Boeing 737. They may also be similar by design, as they belong to the same suite as, for instance, the Microsoft Office software suite, where several tools are designed to be used concurrently by the same users. Previous work on similarity has focused on the visual presentation of interactive applications, highlighting commonalities and differences in terms of layout, shape, colours and other features of the user interface. This paper proposes a systematic and formal approach to analyse and assess the similarity between several interactive systems, focusing on their behaviours. To this end, we propose a tool-supported process that exploits both interactive formal system behaviour models and user task models. These models are analysed with the help of formal tools (model checking) to identify commonalities and differences in their exhibited behaviours. Beyond, we compare the specific and generic behavioural properties of each model, which provide semantic and meaningful information about how similar they are and how they differ. The approach is applied to two similar critical command and control interactive systems for flight safety operations in the space domain.

Welcome to this issue of the Proceedings of the ACM on Human-Computer Interaction, bringing together contributions from the community on Engineering Interactive Computing Systems (EICS). The EICS track of the PACMHCI is the primary venue for research contributions at the intersection of Human-Computer Interaction (HCI) and Software Engineering, and highlights the current advances of the EICS community. This year, over the three rounds of submissions, we received 95 valid submissions (out of 130 submissions in total), of which we carefully selected 28 papers, bringing our acceptance rate to 29,4%. The result of this selection process is presented in this issue of the Proceedings of the ACM. Authors are invited to present their work at EICS 2026, held June 30 to July 3, 2026, in Patras, Greece. This issue presents contributions that embrace current evolutions in engineering interactive computing systems, including topics on techniques and toolkits to develop interactions involving gestures and micro-gestures, tool support for user evaluation methods, toolkits for VR application development, as well as development frameworks for user training applications. In addition, we have contributions in line with current trends on generative AI and eXplainable AI, in particular for engineering the human-AI collaboration and the UI adaptation. At last, several contributions address core EICS themes such as modeling and development tools, as well as design and prototyping support. Our editorial process followed a rigorous three-round, double-blind review. We are grateful to our 28 Track Editorial Board members, who coordinated expert reviews and constructive discussions, and to the 41 external reviewers. We would like to thank all of them, who have ensured that the articles in this issue were rigorously reviewed to form a collection of high-quality papers on the theme of EICS.

Operators of critical systems (e.g., air traffic controllers, pilots in commercial aircraft, operators managing space vehicle launch…) must acquire specific knowledge before being granted permission to perform their tasks on the job. They acquire such knowledge by following a training program developed for the specific tasks they will be doing. The preparation of their training program requires identifying the knowledge they have to acquire, and in particular, the two main types of knowledge that are declarative knowledge (a set of concepts required to operate a system) and procedural knowledge (a set of tasks required to operate a system). Task analysis techniques were originally proposed for the purpose of identifying and describing the knowledge required by users to interact with a system. These techniques provide support to describe procedural knowledge in detail, and a few of them provide limited support to describe declarative knowledge. In this paper, we propose a model-based technique to exhaustively identify and describe declarative and procedural knowledge, as well as to couple the different types of models in order to ensure the full coverage and consistency of the identification of knowledge required to operate an interactive system. We present the results from the application of the technique on a case study in the space domain.

Designing new input devices and associated interaction techniques is a key contribution in order to increase the bandwidth between users and interactive applications. In the field of Human-Computer Interaction, research and development services in industry and research laboratories in universities have been, since the invention of the mouse and the graphical user interface, proposing multiple contributions including the integration of multiple input devices in multimodal interaction technique. Those contributions, most of the time, are presented as prototypes or demonstrators providing evidence of the bandwidth increase through user studies. Such contributions however, do not provide any support to software developers for integrating them in real-life systems. When done, this integration is performed in a craft manner, outside required software engineering good practice. This paper proposes a systematic process to integrate novel input devices and associated interaction techniques to better support users' work. It exploits most recent interactive systems architectural model and formal model-based approaches for interactive systems supporting verification and validation when required. The paper focusses on Frame-based input devices which support gesture-based interactions and movements recognition but also addresses their multimodal use. This engineering approach is demonstrated on an interactive application in the area of rehabilitation in healthcare where dependability of interactions and applications is as critical as their usability.

Post-stroke or post-brain injuries rehabilitation is a long-term process defined by therapists and tuned to the specific damages and their consequences for each patient. This process requires the definition of well-defined multiple exercises to be performed multiple times by each patient over a long period of time. One of the key findings in the rehabilitation domain is that exercises should be tasks and goals oriented to increase functional independence, enhance development and prevent disability [24]. Patients performing the exercises must be carefully monitored to identify progress, possible regression and prevent damages due to the inadequate performance of the exercises. The SIVIRE tool [20] provides interactive graphical feedback to patients about the performance of their exercises and deviations from nominal, planed practice but fails at providing high-level descriptions of exercises and at connecting them to high-level rehabilitation goals (e.g. gain autonomy in cleaning a room). The HAMSTERS-XLE tool [16] provides a tuneable editor and a simulator to describe goals and task models including low-level tasks covering perception of the various senses, cognition and motoric actions. This paper presents the integration of these two tools and the benefits it brings both to the patients and to the therapists. The resulting tool and its engineering are presented in detail highlighting some generic integration mechanisms. On a case study, we show how exercises can be defined in HAMSTERS-XLE, transferred to SIVRE for fine tuning, monitored by SIVRE during the multiple practices of the patient and transferred back again to HAMSTERS-XLE to monitor progress, identify issues with the exercises and provide therapists with goal and task-based data about patients' evolutions

In this paper, a task model based on HAMSTERS-XL notation is proposed to represent activities of daily living (ADL). For an efficient representation of ADL, it is also a need to delimit requirements in time and location for each ADL, as well as the sensor data that define the ADL. In this sense, it is also proposed a procedure consisting of a set of step intending to delimit such time and location requirements, regarding both activities and sensors; alongside the events that need to be identified. The presented approach aims at providing an analysis tool regarding the performance of elderly/handicapped people by comparing data recovered from sensors within a smart home environment simulator to the task models. The feed oneself ADL (as well as its possible variations) is picked in order to evaluate our proposal. After proper analysis was carried out, anomalies detected during ADL performance are pointed out in order to detect possible ADL routine modification in a coherent manner through improved task models.

Training operators of complex interactive systems is a difficult task that involves multiple actors, requires specific competencies and may be extremely costly in terms of time and resources. For instance, an initial training has to be performed in order to bring operators to a desired level of declarative and procedural knowledge. A successful operator will be granted a qualification to operate the system that was used for (or targeted by) the training. However, depending on the nature and the diversity of the operations performed on a daily basis, this initial training may decay and some knowledge may become deprecated. Recurrent training needs to be organised on a regular basis in order to keep operators qualified for the work. Such training differs from initial training and requires taking into account information about how humans learn and forget, what has been performed by operators since last training and the expected required level of knowledge. Trainers need to encompass all this generic information (to all operators) and specific information (to each individual) to define both initial and recurrent training programs. One particularly cumbersome task is the gathering of what happened during operations for each operator in order to minimize recurrent training program to knowledge that might have been forgotten as it was not used in recent operations. We propose a tool-supported task-model approach fed by information of the real work of operators in order to identify complete, relevant and efficient training for operators. These contributions have been applied to the civil aviation domain demonstrating multiple induced benefits.

Abstract Training operators to efficiently operate critical systems is a cumbersome and costly activity. A training program aims at modifying operators’ knowledge and skills about the system they will operate. The design, implementation and evaluation of a ‘good’ training program is a complex activity that requires involving multi-disciplinary work from multiple stakeholders. This paper proposes the combined use of task descriptions and augmented reality (AR) technologies to support training activities both for trainees and instructors. AR interactions offer the unique benefit of bringing together the cyber and the physical aspects of an aircraft cockpit, thus providing support to training in this context that cannot be achieved by software tutoring systems. On the instructor side, the LeaFT-MixeR system supports the systematic coverage of planed tasks as well as the constant monitoring of trainee performance. On the trainee side, LeaFT-MixeR provides real-time AR information supporting the identification of objects with which to interact, in order to perform the planned task. The paper presents the engineering principles and their implementation to bring together AR technologies and tool-supported task models. We show how these principles are embedded in LeaFT-MixeR system as well as its application to the training of flight procedures in aircraft cockpits.

The goal of software testing is to detect defects with the objective of removing them at a later stage in the development process. Interactive software development follows the User Centered Design approach that promotes continuous involvement of users both at design and evaluation phases. This process is meant to produce usable interactive software by gathering functional and non-functional requirements related to both user needs and context of use. However, taking into account these potentially very-complex-to-implement requirements increases the complexity of the software that is likely, without appropriate methods and tools, to encompass a large number of defects. One of the limitations of UCD approaches is that it provides no guidance on the engineering of the interactive application, which thus usually embeds numerous defects resulting in failures at the origin of user frustrations and performance drops. Even though a classification of interactive application defects has been proposed, interactive application testers remain only superficially supported in detecting them. This paper defines a model-based approach to engineer the testing activity for interactive applications. It proposes a process that bridges the gap between UCD artefacts and interactive software implementation by the production of a dedicated formal model exploited for testing purposes only. The application of the process is demonstrated on an interactive cockpit WIMP application. Finally, threats to validity (capability of the approach to detect defects and to ensure an acceptable coverage testing of the interactive application) are addressed by a longitudinal study on 61 variants of a simple application developed by 61 different developers. ?

Use error due to user interface design defects is a major concern in many safety critical domains, for example avionics and health care. Early detection of latent user interface problems can be facilitated by user-centered design methods that integrate formal verification technologies. This article considers the role that formal verification technologies can play in the context of user-centered design by considering the following three existing tools: CIRCUS, PVSio-web, and IVY. These tools have been developed to support the model based analysis of critical user interfaces. They have their foundations in existing formal verification technologies, but each of them is focused towards particular issues relating to user interface design. The article explores the different phases of the user-centered design process and the extent to which each of these tools supports these phases. Criteria are developed for assessing their role at each stage of the design process. The results of the evaluation provide guidance to developers to help choose the most appropriate tool based on their analysis needs while at the same time setting challenges for future developments.

When task descriptions are precise they can be analysed to yield a variety of insights about interaction, such as the quantity of actions performed, the amount of information that must be perceived, and the cognitive workload involved. Task modelling notations and associated tools provide support for precise task description, but they generally provide a fixed set of constructs, which can limit their ability to model new and evolving application domains and technologies. This article describes challenges involved in using fixed notations for describing tasks. We use examples of recognized tasks analysis processes and their phases to show the need for customization of task notations, and through a series of illustrative examples, we demonstrate the benefits using our extensible task notation and tool (HAMSTERS-XL).

Ensuring that an interactive application allows users to perform their activities and reach their goals is critical to the overall usability of the interactive application. Indeed, the effectiveness factor of usability directly refers to this capability. Assessing effectiveness is a real challenge for usability testing as usability tests only cover a very limited number of tasks and activities. This paper proposes an approach towards automated testing of effectiveness of interactive applications. To this end we resort to two main elements: an exhaustive description of users' activities and goals using task models, and the generation of scenarios (from the task models) to be tested over the application. However, the number of scenarios can be very high (beyond the computing capabilities of machines) and we might end up testing multiple similar scenarios. In order to overcome these problems, we propose strategies based on task models manipulations (e.g., manipulating task nodes, operator nodes, information...) resulting in a more intelligent test case generation approach. For each strategy, we investigate its relevance (both in terms of test case generation and in terms of validity compared to the original task models) and we illustrate it with a small example. Finally, the proposed strategies are applied on a real-size case study demonstrating their relevance and validity to test interactive applications.

User interfaces for the command and control of transportation and navigation systems, such as aircraft cockpits, usually integrate several types of interaction elements: physical, hardware or software. Within these cyber-physical environments, operators have to complete their tasks manipulating these different types of elements. However, task description notations do not take into account physical and hardware aspects beyond manipulation of input devices such as mouse and keyboard. This paper identifies generic aspects of cyber-physical interactive systems and proposes extensions to operators' tasks description techniques, to capture them. We argue that representing cyber-physical elements explicitly and systematically in task models contribute to the design and development of usable and reliable transportation systems. These extensions are integrated within the tool-supported notation called HAMSTERS and are illustrated on a case study from the avionics domain.

The overall dependability of an interactive system is one of its weakest components, which is usually its user interface. The presented approach integrates techniques from the dependable computing field and elements of the user-centered design. Risk analysis and fault-tolerance techniques are used in combination with task analysis and modeling to describe and analyze the impact of system faults on human activities and the impact of human deviation or errors on system performance and overall mission performance. A technique for systematic analysis of human errors, effects, and criticality (HEECA) is proposed. It is inspired and adapted from the Failure Mode, Effects, and Criticality Analysis technique. The key points of the approach are: 1) the HEECA technique combining a systematic analysis of the effects of system faults and of human errors; and 2) a task modeling notation to describe and to assess the impact of system faults and human errors on operators' activities and system performance. These key points are illustrated on an example extracted from a case study of the space domain. It demonstrates the feasibility of this approach as well as its benefits in terms of identifying opportunities for redesigning the system, redesigning the operations, and for modifying operators' training.

Designing systems in such a way that as much functions as possible are automated has been the driving direction of research and engineering in aviation, space and more generally in computer science for many years. In the 90's many studies (e.g. [12] related to the notion of mode confusion) have demonstrated that fully automated systems are out of the grasp of current technologies and that additionally migrating functions [2] from the operator to the system might have disastrous impact on operations both in terms of safety and usability. In order to be able to design automation with a hedonic view of the involved factors (safety, usability, reliability, ...) a complete understanding of operator's tasks is required prior to considering migrating them to the system side. This paper proposes a contribution for reasoning about automation designs using a model-based approach exploiting refined task models. These models describe operations with enough details in order to reason about automation and to rationalize automation designs. In this paper we present how such representations can support the assessment of alternative design options for automation. The proposed approach is applied to satellite ground segments.