PublicationsAll

The lack of a common executable modeling framework that integrates systems engineering, software design, and other engineering domains is a major impediment to seamless product development processes. Our research aims to overcome this system-software modeling gap by integrating computational, software-related, and model execution capabilities into OPM-based conceptual modeling, resulting in a holistic unified executable quantitative-qualitative modeling framework. The gap is overcome via a Methodical Approach to Executable Integrative Modeling—MAXIM, an extension of OPM ISO 19450:2015, a standardization approvement given on 2015. We present the principles of MAXIM and demonstrate its operation within OPCloud—a web-based collaborative conceptual OPM modeling framework. As a proof-of-concept, a model of an Airbus civil aircraft landing gear braking system is constructed and executed. Using MAXIM, engineers from five domains can collaborate at the very early phase of the system development and jointly construct a unified model that fuses qualitative and quantitative aspects of the various disciplines. This case study illustrates an important first step towards satisfying the critical and growing need to integrate systems engineering with software computations into a unified framework that enables a smooth transition from high-level architecting to detailed, discipline-oriented design. Such a framework is a key to agile yet robust future development of software-intensive systems.

As science and technology create an ecosystem that is becoming increasingly more knowledge-intensive, complex, and interconnected, the next generation science standards include systems thinking and systems modeling among 21^st skills that should be fostered. We examined the effect of an online cross-disciplinary learning process on the development of systems thinking and modeling skills among engineering students and engineering and science teachers. The study, which used quantitative and qualitative tools, included 55 participants who performed four food-related learning assignments and created conceptual models in Object-Process Methodology. Their responses to online assignments were analyzed along with their perceptions, captured via a reflection questionnaire. The online learning process in this study effectively enhanced the systems thinking and modeling skills of all learners, including those with no relevant background. One main conclusion that extends beyond online learning was that imparting the basics of systems thinking and conceptual modeling skills can be achieved even within a short period of time – less than one semester. The contribution of the study is the formation of theoretical and practical frameworks for the integration of cross-disciplinary model-based systems engineering online assignments into engineering and science curricula.

Objective: Pediatric Failure To Thrive (FTT), commonly presented in young infants, is often not diagnosed on time or missed. Lack of timely infants’ diagnosis can adversely affect their growth and development. We have developed and successfully tested FTTell—a model-based system for diagnosing FTT during common pediatric follow up.

Materials and Methods:  FTTell is an executable model-based diagnostic tool for assessing potential FTT during the postnatal stage. We use Object-Process Methodology extended with Methodical Approach to Executable Integrative Modeling, enabling qualitative considerations and quantitative parameters of the problem to be modeled jointly, enabling FTT diagnosis.

Results: The validity of FTTell is demonstrated on data collected from 100 infants. For each child, FTTell calculates a score that indicates FTT presence and severity. We compared the outcomes of the system to a pediatric gastroenterologist expert severity assessment. Of the 100 infants, the system initially diagnosed 82 as having FTT, which were diagnosed by the expert as well. Reassessment of the remaining infants yielded 87% efficacy.

Discussion: Pediatricians may miss infants with FTT, especially in borderline cases. FTTell can effectively serve as a FTT diagnosis tool, boosting pediatricians’ correct diagnosis and proper investigation. Our cloud-based system can be continuously updated with the latest research findings.

Conclusion: FTTell can diagnose FTT and its severity in infants with 87% accuracy. Pediatricians can use this model-based standardized approach to improve their FTT diagnosis and provide appropriate timely intervention when needed. Model-based diagnosis is a novel application of conceptual models, and OPM ISO 19450 is especially fit for this purpose. The model-based diagnosis approach can be extended beyond medicine to diagnosing problems with engineered, technological, and socio-technical systems.

As part of the design, development, and deployment of a massive open online course (MOOC) on model-based systems engineering, we introduced MORTIF—Modeling with Real-Time Informative Feedback, a new learning-by-doing feature that enables the learner to model, receive detailed feedback, and resubmit improved solutions. We examined the pedagogical usability of MORTIF by investigating characteristics of participants working with it, and their perceived contribution, preferred question type, and learning style. The research included 295 participants and applied the mixed-methods approach, using MOOC server data and online questionnaires. Analyzing 12,095 submissions, we found increasing frequency of using the model resubmitting option. Students ranked MORTIF as the highest of six question types in terms of preference and perceived contribution level. Nine learning style categories were identified and classified based on students’ verbal explanations regarding their preference of MORTIF over the other question types. MORTIF has been effective in promoting meaningful learning, supporting our hypothesis that the combination of active learning with real-time informative feedback is a learning mode that students eagerly embrace and benefit from. The benefits we identified for using MORTIF include active learning, provision of meaningful immediate feedback to the learner, the option to use the feedback on the spot and resubmitting an improved model, and its suitability for a variety of learning styles.

Modern systems comprise hardware and software components that together provide value through enabling the functionality that the system is intended to provide. Systems engineering (SE) and software engineering (SwE) are therefore interdependent, tightly coupled, and complementary activities that must be carefully aligned and coordinated throughout the system development process. Yet, these two disciplines have historically grown quite separated from each other, with too little interaction and mutual learning. In this work, we develop and evaluate Object-Process Programming (OPP) as a proof-of-concept for a common framework that integrates SE and SwE based on ISO 19450— Object-ProcessMethodology. The ability of designers to use the same paradigm for engineering the software, the hardware, and the system as a whole, using the same concepts and principles and the same design environment, described and discussed in this work, is a major step toward the integration and streamlining of engineering new systems that feature significant hardware and software components. To evaluate OPP, we established a focus group and conducted an experiment in which participants were asked to develop systems using OPP. Overall, the results were positive in terms of usability and understandability. In particular, the language and the environment were far superior in comparison to textual languages. OPP will contribute to the continuous endeavor to bridge the gap between SE and SwE by providing a seamless, easy-to-learn environment. Non-technical stakeholders can also benefit from OPP by improving their communication with technical stakeholders. The ideas under lying OPP have already served to augment OPM with computational capabilities.

Models have traditionally been mostly either prescriptive, expressing the function, structure and behavior of a system-to-be, or descriptive, specifying a system so it can be understood and analyzed. In this work, we offer a third kind—diagnostic models. We have built a model for assessing potential pediatric failure to thrive (FTT) during the perinatal stage. Although FTT is commonly found in young children and has been studied extensively, the exact etiology is often not clear. The ideal solution is for a pediatrician to input pertinent data and information in a single tool in order to obtain some assessment on the
potential etiology. We present FTTell—an executable model-based medical knowledge aggregation and diagnosis tool, in which the qualitative considerations and quantitative parameters of the problem are modeled using a Methodical Approach to Executable Integrative Modeling (MAXIM)—an extended version of Object-Process Methodology (OPM) ISO 19450, focusing on the perinatal stage. The efficacy of the tool is demonstrated on three real-life cases, and the tool’s diagnosis outcomes may be compared with and critiqued by a domain expert.

We have designed, developed and deployed a unique edX massive open online course (MOOC) environment for teaching Model-Based Systems Engineering (MBSE) with Object-Process Methodology (OPM) ISO 19450. In this environment, OPCloud, an OPM cloud-based conceptual modeling environment, has been embedded in the edX environment. This has enabled us, as the course instructors, to teach MBSE with an industrial-strength tool that students can experience first-hand. Students received real-time feedback on their performance, along with guidance on what they missed and the option to resubmit. We describe the architecture of this combined MOOC-modeling environment and report on preliminary performance results.

We have designed, developed and deployed a unique edX massive open online course (MOOC) environment for teaching Model-Based Systems Engineering (MBSE) with Object-Process Methodology (OPM) ISO 19450. In this environment, OPCloud, an OPM cloud-based conceptual modeling environment, has been embedded in the edX environment. This has enabled us, as the course instructors, to teach MBSE with an industrial-strength tool that students can experience first-hand. Students received real-time feedback on their performance, along with guidance on what they missed and the option to resubmit. We describe the architecture of this combined MOOC-modeling environment and report on preliminary performance results.

Models have traditionally been mostly either prescriptive, expressing the function, structure and behavior of a system-to-be, or descriptive, specifying a system so it can be understood and analyzed. In this work, we offer a third kind—diagnostic models. We have built a model for assessing potential pediatric failure to thrive (FTT) during the perinatal stage. Although FTT is commonly found in young children and has been studied extensively, the exact etiology is often not clear. The ideal solution is for a pediatrician to input pertinent data and information in a single tool in order to obtain some assessment on the
potential etiology. We present FTTell—an executable model-based medical knowledge aggregation and diagnosis tool, in which the qualitative considerations and quantitative parameters of the problem are modeled using a Methodical Approach to Executable Integrative Modeling (MAXIM)—an extended version of Object-Process Methodology (OPM) ISO 19450, focusing on the perinatal stage. The efficacy of the tool is demonstrated on three real-life cases, and the tool’s diagnosis outcomes may be compared with and critiqued by a domain expert.

Modeling is an important part of the lifecycle of systems, starting from the early design stages. Modeling is also very useful in the process of studying an unfamiliar, existing system. Conceptual modeling methodologies disregard certain aspects of the system, making modeling or understanding a model a simpler task as they convey the important aspects of a system in an effective way.

One of the shortcomings of conceptual modeling methodologies is the simplification of the system being modeled at the expense of suppressing computational aspects. This research presents two approaches for solving this computational simplification problem for conceptual models that use Object Process Methodology (OPM), an emerging ISO 19450 standard modeling methodology.

OPM offers a holistic approach for modeling systems that combines the structure and behavior of the system in a single diagram type. We expand the quantitative aspects of an OPM model by representing complex quantitative behavior using alternative approaches that employ MATLAB or Simulink without compromising the holism and simplicity of the OPM conceptual model. The first approach, AUTOMATLAB, expands the OPM model to a fullfledged MATLAB-based simulation. The second, OPM Computational Subcontractor approach, replaces low-level processes of the OPM model with computation-enhanced MATLAB functions or Simulink models.

We demonstrated the two approaches with MATLAB and Simulink enhanced OPM models of a biological system and a radar system, respectively. An evaluation the AUTOMATLAB approach, which compared system modeling and analysis with and without the AUTOMATLAB layer has indicated several benefits of the additional AUTOMATLAB layer compared to a non-enhanced OPM model.

Model-based engineering approaches are increasingly adopted for various systems engineering tasks. Leading characteristics of modeling languages include clarity, expressiveness and comprehension. Exact semantics of the modeling language used in a model-based framework is critical for a successful system development process. As some of the characteristics contradict each other, designing a “good” modeling language is a complex task. Still, an important precondition for acceptance of a modeling language is that its semantics must be precisely and formally defined.

Object Process Methodology (OPM) is a holistic, integrated model-based approach to systems development. The applicability of the OPM modeling language was studied through modeling of many complex systems from disparate domains, including business processing, real-time systems architecture, web applications development and mobile agents design. Experience with OPM has underlined the need to enrich the language with new constructs. An adverse side effect of the increased OPM expressiveness was that it also became more complex and in some cases ambiguous or undefined.

In this work, we define operational semantics for the core of the OPM language using a clocked transition system (CTS) formalism. The operational semantics consists of an execution framework and a set of transition rules. The principles and rules underlying this framework provide for determining the timing of transitions to be taken in a system modeled in OPM. The set of transition rules, adjusted to the OPM rules, describe all the possible changes in the system state based on the current state of the system and the set of its inputs.

Similar works defining formal operational semantics include Statecharts by David Harel, formalizing UML Statecharts with combined graph-grammar and model transition system (MTS) by Varro et al., and formalizing activ1ity diagrams for workflow models by translating the subject model into a format appropriate for a model checker.

Well-defined operational semantics enables extending OPM with a wide range of testing tools, including model-based simulation, execution and verification, which can employ the theoretical executable framework developed in this work.

As a solid proof of concept, we have developed an OPM-to-SMV (Symbolic Model Verification) translation tool for models in the domain of Molecular Biology (MB), based on the OPM-CTS framework principles and a subset of the transition rules. Using this tool, a holistic OPM model describing both research hypothesis and facts from state-of-the-art MB papers can be translated into an SMV verification tool. The generated SMV model can be verified against specifications, based on information found in MB research papers and manually inserted into the SMV tool. The verification process helps to reveal possible inconsistencies across the MB papers and hypotheses they express as they are all specified in the unifying OPM model.

Project and product are two complementary facets of the lifecycle of any complex man-made system. The project focuses on the early phases of the system to be delivered, deployed, and supported, while the product focuses on the system itself – its function, structure, and behavior. Conceptual modelling and design is a major area common to both the project and the product, since evidently, the product is the deliverable of the project. Traditionally, however, the project and the product entities have been addressed as separate domains, each with its dedicated approaches, methods, and tools. This separation has hindered the integration of the project with the product it delivers, missing potential tangible benefits for all the stakeholders involved. Systems Engineering Management (SEM) is an emerging practice that is being developed hand in hand with the maturation of systems engineering. Standards for SEM account for the intimate relationships between SEM and Project Management (PM) and highlight the criticality of these relationships in improving systems project management. While PM methods have traditionally focused on scheduling, budgeting, and scope management, SEM emphasizes the management of the project-product ensemble and issues related to the technologies of the system under development. The actual practice of systems engineering management involves continuous iterative zigzagging between the two domains – the systems engineering domain and the project management domain. This zigzagging is a cognitive process of understanding the intricate relationships between the product domain and the project domain, and planning the SEM efforts accordingly. What the product-project ensemble has been lacking is a common underlying ontology, a conceptual model, and a supporting software environment. Attaining these missing elements enables the simultaneous expression of the function, structure and behavior of the project and the product. This thesis presents a model-based approach to managing the lifecycle of the product to be developed hand-in-hand with the lifecycle of the project, within the scope of which the product is developed. The cornerstone of this Project-Product Lifecycle Management (PPLM) approach is an underlying holistic conceptual model, supported by software capabilities for an integrated project and product lifecycle environment. The concurrent project-product model, built on common ontological foundations, enables better management, making it possible to directly link entities in one subsystem to those in the other. The expected value of the holistic, integrated conceptual model is the provision of both superior product lifecycle engineering and project management capabilities, yielding significant cut in time to market, reduced risk, and higher product quality.