xFFBD: towards a formal yet functional modeling language for system designers

Although the eFFBD formalism dates back to the 1990s (or even, in a simplified form, the 1950s), it seems that it is still not as much used by the Systems Engineering community as it could. Indeed, eFFBD is a modeling language focusing on functional paradigm i.e. allowing functional and behavioral modeling and reasoning about a system. Currently, it is often confronted or compared to other languages such as SysML for activity modeling (activity diagrams) based on object paradigm. This paper aims to demonstrate the interest and the potential advantages for systems designers, like most of the discipline-oriented designers to dispose of an enriched (conceptually and semantically) eFFBD modeling language called here xFFBD. This has to be a credible framework for modeling, communicating and reasoning about complex systems. After shortly recalling the history, the key concepts and capabilities of eFFBD, this paper compares eFFBD with other formalisms considered here as relevant for the study, Petri nets and SysML. Several leads are then identified and discussed in order to improve the eFFBD language and to provide a first draft version of xFFBD specification

A paradigmatic approach of the architectural design of artificial complex systems

L'architecture système cherche à se distinguer de son domaine d'origine, l'ingénierie système, en devenant un domaine émergent. Loin d'être reconnue en tant que science ou discipline à proprement parler, sa pratique est de plus en plus répandue de nos jours. Cependant, cette pratique reste encore peu formalisée et peu enseignée, faute d'un corpus de connaissances, de techniques ou de démarches établi et accessible.Notre thèse contribue à combler ce manque en proposant un paradigme de la conception architecturale des systèmes artificiels complexes. Ce dernier est construit en se basant sur des paradigmes existants, en les combinant, puis en les complétant. Il vise à doter l'architecte de systèmes artificiels complexes d'un cadre opérant, voire performatif. Il se traduit par une structuration de la démarche de conception en quatre niveaux.Un niveau dit archétypal condense les grands principes de toute démarche de conception architecturale de systèmes artificiels complexes. Ces principes sont dérivés de diverses démarches déjà appliquées, principalement à la conception de systèmes ou de produits, mais également à la conception architecturale de bâtiments.Un niveau dit général repose sur le principe d'une partition présent-futur, se différenciant en cela des approches d'ingénierie qui s'appuient traditionnellement sur une dichotomie problème-solution. L'idée prépondérante tient dans l'assentiment que lorsqu'un architecte conçoit, il ne résout pas de problèmes, mais il imagine des futurs possibles et plausibles, nécessitant qu'il perçoive le présent. Cette vision impacte directement la nature des artéfacts sur lesquels il travaille. Nous proposons ensuite d'agréger ces artéfacts en des modèles, reflétant soit sa perception du présent, soit son élaboration des futurs, évoluant suivant des processus identifiés.Un niveau dit particulier a pour objectif de permettre la narration d'une conception particulière. Nous proposons pour cela une notation de la conception. Elle s'appuie sur un certain nombre de mécanismes élémentaires, dont celui de l'enchaînement divergence-convergence, que nous nommons mécanisme de respiration de la conception architecturale.Un niveau dit de boîte à outils n'est pas traité dans le cadre de cette thèse. Il comprendrait les différentes opérations cognitives nécessaires à l'architecte pour accomplir sa tâche de conception (abstraction, questionnement, jugement, comparaison, décision, etc.)L'approche proposée est illustrée par un exemple de conception architecturale d'un système complexe : « rendre une ville plus sûre » (connu dans la littérature anglo-saxonne comme Safe City).Architecting seeks now to be distinct from its original domain, systems engineering, becoming an emergent domain. Far from being recognized as a science or a discipline, its practice is nowadays more and more widespread. However, this practice is still poorly formalized, and insufficiently being taught, lacking a well-established and accessible corpus of knowledge, techniques or approaches.This thesis contributes filling that gap by proposing a paradigm of the architectural design of artificial complex systems. The latter is built based on existing paradigms that are combined, then completed. It aims at providing architects with an effective, even performative framework. It results in an approach of the architectural design structured in four levels.A so-called archetypal level grasps the core principles of any approach of architectural design of artificial complex systems. These principles are derived from various approaches already applied, mainly in the field of system or product design, but also of architectural design of buildings.A so-called general level lies on the principle of a present-future division. In that sense, it differs from engineering approaches that usually rely on a problem-solution dichotomy. It is based on the following main idea: we should consent that when an architect designs, he does not solve problems, but he devises possible and plausible futures, requiring to perceive the present. This vision of the architect's way of working directly impacts the kind of artefacts he handles. We sho how to aggregate these artefacts into models, reflecting either his perception of the present, or his development of futures while progressing through some identified processes.A so-called particular level aims at allowing the storytelling of a given design. To achieve this goal, a notation of the design process is suggested. It lies on some basic mechanisms, one of them being the combination divergence-convergence, called the breathing of the architectural design.At last, a so-called toolbox level, not addressed in this thesis, would consist of various cognitive operations required for the architect in order to accomplish his task of designing (abstraction, questioning, judgement, comparison, decision, etc.)The whole approach is illustrated by an example of an architectural design of a complex system: a Safe City

Une approche paradigmatique de la conception architecturale des systèmes artificiels complexes

Architecting seeks now to be distinct from its original domain, systems engineering, becoming an emergent domain. Far from being recognized as a science or a discipline, its practice is nowadays more and more widespread. However, this practice is still poorly formalized, and insufficiently being taught, lacking a well-established and accessible corpus of knowledge, techniques or approaches.This thesis contributes filling that gap by proposing a paradigm of the architectural design of artificial complex systems. The latter is built based on existing paradigms that are combined, then completed. It aims at providing architects with an effective, even performative framework. It results in an approach of the architectural design structured in four levels.A so-called archetypal level grasps the core principles of any approach of architectural design of artificial complex systems. These principles are derived from various approaches already applied, mainly in the field of system or product design, but also of architectural design of buildings.A so-called general level lies on the principle of a present-future division. In that sense, it differs from engineering approaches that usually rely on a problem-solution dichotomy. It is based on the following main idea: we should consent that when an architect designs, he does not solve problems, but he devises possible and plausible futures, requiring to perceive the present. This vision of the architect's way of working directly impacts the kind of artefacts he handles. We sho how to aggregate these artefacts into models, reflecting either his perception of the present, or his development of futures while progressing through some identified processes.A so-called particular level aims at allowing the storytelling of a given design. To achieve this goal, a notation of the design process is suggested. It lies on some basic mechanisms, one of them being the combination divergence-convergence, called the breathing of the architectural design.At last, a so-called toolbox level, not addressed in this thesis, would consist of various cognitive operations required for the architect in order to accomplish his task of designing (abstraction, questioning, judgement, comparison, decision, etc.)The whole approach is illustrated by an example of an architectural design of a complex system: a Safe City.L'architecture système cherche à se distinguer de son domaine d'origine, l'ingénierie système, en devenant un domaine émergent. Loin d'être reconnue en tant que science ou discipline à proprement parler, sa pratique est de plus en plus répandue de nos jours. Cependant, cette pratique reste encore peu formalisée et peu enseignée, faute d'un corpus de connaissances, de techniques ou de démarches établi et accessible.Notre thèse contribue à combler ce manque en proposant un paradigme de la conception architecturale des systèmes artificiels complexes. Ce dernier est construit en se basant sur des paradigmes existants, en les combinant, puis en les complétant. Il vise à doter l'architecte de systèmes artificiels complexes d'un cadre opérant, voire performatif. Il se traduit par une structuration de la démarche de conception en quatre niveaux.Un niveau dit archétypal condense les grands principes de toute démarche de conception architecturale de systèmes artificiels complexes. Ces principes sont dérivés de diverses démarches déjà appliquées, principalement à la conception de systèmes ou de produits, mais également à la conception architecturale de bâtiments.Un niveau dit général repose sur le principe d'une partition présent-futur, se différenciant en cela des approches d'ingénierie qui s'appuient traditionnellement sur une dichotomie problème-solution. L'idée prépondérante tient dans l'assentiment que lorsqu'un architecte conçoit, il ne résout pas de problèmes, mais il imagine des futurs possibles et plausibles, nécessitant qu'il perçoive le présent. Cette vision impacte directement la nature des artéfacts sur lesquels il travaille. Nous proposons ensuite d'agréger ces artéfacts en des modèles, reflétant soit sa perception du présent, soit son élaboration des futurs, évoluant suivant des processus identifiés.Un niveau dit particulier a pour objectif de permettre la narration d'une conception particulière. Nous proposons pour cela une notation de la conception. Elle s'appuie sur un certain nombre de mécanismes élémentaires, dont celui de l'enchaînement divergence-convergence, que nous nommons mécanisme de respiration de la conception architecturale.Un niveau dit de boîte à outils n'est pas traité dans le cadre de cette thèse. Il comprendrait les différentes opérations cognitives nécessaires à l'architecte pour accomplir sa tâche de conception (abstraction, questionnement, jugement, comparaison, décision, etc.)L'approche proposée est illustrée par un exemple de conception architecturale d'un système complexe : « rendre une ville plus sûre » (connu dans la littérature anglo-saxonne comme Safe City)

Anticipating Integration, Verification and Validation

International audienc

Solving the Problem Completely, in a Coherent and Optimal Manner

International audienc

A Design Pattern Metamodel and Use Mechanisms for Systems Engineering

International audienceIn facing repetitive classes of problems during their projects, engineers need to combine practitioners' experience in design with solutions that are already capitalized, approved, and standardized. Sharing, interpreting, and applying this experience and these solutions allows engineers to improve their performance (including comprehensiveness and relevance) and their reliability (since they are using proven solutions that have been justified and argued contextually), while also raising their economic value (through time savings). In this way enterprises can capitalize on their engineers' experience. The idea of using such "design patterns" is intended to help an engineer improve the nonfunctional features, quality of service, and "ilities" (Manola 1999) of a system under design. A design pattern is a simple and small artifact, linking a model of a problem noticed in a given context with a model of a well-known solution that has been already used to solve the problem in another but quite similar context on which the interest of the solution has been validated. This solution must then be imitated and adapted to another context. This approach is currently used in several engineering fields, such as traditional architecture, software engineering, and process management. More recently it has been applied to systems engineering. Despite this literature, however, the design-pattern concept remains poorly formalized for the systems engineering domain. Our research promotes a formalized metamodel for design patterns

A Design Pattern Metamodel and Use Mechanisms for Systems Engineering

International audienceIn facing repetitive classes of problems during their projects, engineers need to combine practitioners' experience in design with solutions that are already capitalized, approved, and standardized. Sharing, interpreting, and applying this experience and these solutions allows engineers to improve their performance (including comprehensiveness and relevance) and their reliability (since they are using proven solutions that have been justified and argued contextually), while also raising their economic value (through time savings). In this way enterprises can capitalize on their engineers' experience. The idea of using such "design patterns" is intended to help an engineer improve the nonfunctional features, quality of service, and "ilities" (Manola 1999) of a system under design. A design pattern is a simple and small artifact, linking a model of a problem noticed in a given context with a model of a well-known solution that has been already used to solve the problem in another but quite similar context on which the interest of the solution has been validated. This solution must then be imitated and adapted to another context. This approach is currently used in several engineering fields, such as traditional architecture, software engineering, and process management. More recently it has been applied to systems engineering. Despite this literature, however, the design-pattern concept remains poorly formalized for the systems engineering domain. Our research promotes a formalized metamodel for design patterns

Health-status outcomes with invasive or conservative care in coronary disease

BACKGROUND In the ISCHEMIA trial, an invasive strategy with angiographic assessment and revascularization did not reduce clinical events among patients with stable ischemic heart disease and moderate or severe ischemia. A secondary objective of the trial was to assess angina-related health status among these patients. METHODS We assessed angina-related symptoms, function, and quality of life with the Seattle Angina Questionnaire (SAQ) at randomization, at months 1.5, 3, and 6, and every 6 months thereafter in participants who had been randomly assigned to an invasive treatment strategy (2295 participants) or a conservative strategy (2322). Mixed-effects cumulative probability models within a Bayesian framework were used to estimate differences between the treatment groups. The primary outcome of this health-status analysis was the SAQ summary score (scores range from 0 to 100, with higher scores indicating better health status). All analyses were performed in the overall population and according to baseline angina frequency. RESULTS At baseline, 35% of patients reported having no angina in the previous month. SAQ summary scores increased in both treatment groups, with increases at 3, 12, and 36 months that were 4.1 points (95% credible interval, 3.2 to 5.0), 4.2 points (95% credible interval, 3.3 to 5.1), and 2.9 points (95% credible interval, 2.2 to 3.7) higher with the invasive strategy than with the conservative strategy. Differences were larger among participants who had more frequent angina at baseline (8.5 vs. 0.1 points at 3 months and 5.3 vs. 1.2 points at 36 months among participants with daily or weekly angina as compared with no angina). CONCLUSIONS In the overall trial population with moderate or severe ischemia, which included 35% of participants without angina at baseline, patients randomly assigned to the invasive strategy had greater improvement in angina-related health status than those assigned to the conservative strategy. The modest mean differences favoring the invasive strategy in the overall group reflected minimal differences among asymptomatic patients and larger differences among patients who had had angina at baseline

Initial invasive or conservative strategy for stable coronary disease

BACKGROUND Among patients with stable coronary disease and moderate or severe ischemia, whether clinical outcomes are better in those who receive an invasive intervention plus medical therapy than in those who receive medical therapy alone is uncertain. METHODS We randomly assigned 5179 patients with moderate or severe ischemia to an initial invasive strategy (angiography and revascularization when feasible) and medical therapy or to an initial conservative strategy of medical therapy alone and angiography if medical therapy failed. The primary outcome was a composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest. A key secondary outcome was death from cardiovascular causes or myocardial infarction. RESULTS Over a median of 3.2 years, 318 primary outcome events occurred in the invasive-strategy group and 352 occurred in the conservative-strategy group. At 6 months, the cumulative event rate was 5.3% in the invasive-strategy group and 3.4% in the conservative-strategy group (difference, 1.9 percentage points; 95% confidence interval [CI], 0.8 to 3.0); at 5 years, the cumulative event rate was 16.4% and 18.2%, respectively (difference, 121.8 percentage points; 95% CI, 124.7 to 1.0). Results were similar with respect to the key secondary outcome. The incidence of the primary outcome was sensitive to the definition of myocardial infarction; a secondary analysis yielded more procedural myocardial infarctions of uncertain clinical importance. There were 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (hazard ratio, 1.05; 95% CI, 0.83 to 1.32). CONCLUSIONS Among patients with stable coronary disease and moderate or severe ischemia, we did not find evidence that an initial invasive strategy, as compared with an initial conservative strategy, reduced the risk of ischemic cardiovascular events or death from any cause over a median of 3.2 years. The trial findings were sensitive to the definition of myocardial infarction that was used