Animation-Based Service Specification, Verification and Validation

[Context] With the expansion of services and service science, service systems have become an important abstraction for the service revolution. Service is defined as the application of resources (including competences, skills, and knowledge) to make changes that have value for another (system). The service system is a configuration of people, technologies, and other resources that interact with other service systems to create mutual value. Many systems can be viewed as service systems, including families, cities, and companies, among many others. Therefore, services became very important for unifying concepts from various disciplines. Service specifications are used to represent service systems on different levels of abstraction: from business down to IT. [Motivation and Problem] Traditionally, high-level service specifications are used only for communication among different participants, to catalyze the discussions between them; but only the specifications modeling IT systems have enough details to be simulated and executed. As a consequence, it becomes difficult to create precise high-level specifications and make sure that the implemented services are those that correspond to the business needs, potentially leading to severe project problems. Therefore, the challenge is to create abstract, yet precise service specifications, while keeping the relation between specifications at different levels of abstraction. [Idea and Results] In this work, we use formal methods and code generation techniques to create service-prototypes from service specifications at any level of abstraction, keeping the relations between different specifications. Stakeholders can try out the prototypes and give feedback regarding services that are being provided. This way, prototypes are used to validate the specifications and detect inconsistencies and unexpected behavior. [Contribution] The contributions of our work are threefold. First, we provide the visual formalism for service specification and simulation, by adding the necessary concepts to the existing method SEAM. Second, we define two design spirals: for service specification and for service validation and verification. The service specification spiral enables us to keep the relation between several service specifications. It includes steps with explicit design decisions on how to refine high-level specifications in order to include all the details necessary for providing the identified services. The validation and verification spiral is used to validate and verify specifications at any level of abstraction. Finally, it provides an environment that enables the simulation and prototyping of service specifications that are then used for their validation and verification. [Relevance] In addition to the theoretical contribution to the knowledge base of service design, we also provide the tools and guidelines that help business and IT analysts create and validate the service model, as confirmed by a survey conducted with practitioners. We illustrate the application of this work with a case study based on a consulting project we conducted at EPFL.

MDA in Enterprise Architecture? The Living System Theory to the Rescue…

Otto Preiss, Alain Wegmann

Integrating business and information technology (IT) is essential for enterprises to be competitive. The integration of business and IT forces project teams to analyze and design a hierarchy of systems such as: groups of companies collaborating in business systems, people and IT systems collaborating in business processes, software components collaborating in IT systems, and programming language objects collaborating in software components. The current tools, and in particular MDA, have not been tailored for the design of hierarchical systems. As a result the project teams have difficulties designing integrated business and IT systems. In this paper we present a technique for supporting the design of hierarchical systems. We were inspired by Millers General Theory of Living System, a theory that addresses the analysis of hierarchical living systems. We provide concrete guidelines on how to introduce levels in UML-based system modeling, in general, and in MDA in particular. This allows the project team to develop one, common, integrated enterprise (or project) model. This in turn enables the different specialists to reason about and design business and IT systems that are truly integrated. The overall benefit is an increase in the project success rate.

2003

Towards a UML Profile for Software Architecture

Mohamed Mancona Kandé

To formally describe architectures of software systems, specific languages called Architecture Description Languages (ADLs) have been developed by academic institutions and research labs. However, more and more research and industrial projects are using the standard Unified Modeling Language (UML) for representing software architectures of systems. In this paper, we focus on how to extend the UML by incorporating some key abstractions found in current ADLs, such as connectors, components and configurations, and how the UML can be used for modeling architectural viewpoints. Our approach is demonstrated by the software architecture of a video surveillance system. It is therefore the purpose of the paper to show that a UML profile for software architecture is needed.

2000

Jet-scheduling control for flat systems

Davide Buccieri

The control of cranes and nonholonomic robots has gained increased interest mainly because of the civilian and military industrial need to achieve fast and accurate transport of goods and equipment. Old and new harbors are now venturing into fully automated systems combining automated trolleys and classical cranes. From a theoretical viewpoint these systems are challenging because they are strongly dynamically coupled and offer interesting and useful control problems. Therefore, to take full advantage of their potential, the control design must take into account as much structural information as possible. The structural property that is exploited in the control design proposed in this thesis is the differential flatness property of these systems, that is the existence of particular functions of the states (called flat outputs), the time parametrization of which implies parametrization of all the individual states and inputs. This property is extremely useful for motion planning problems where the system should move quickly from one configuration to another, without inducing too much overshoot or residual oscillations. However, the flatness property is not sufficient to guarantee the design of an efficient controller in the presence of uncertain and unmodeled dynamics. This is especially the case for cranes where the winching mechanism, expressed in terms of the engine and pulleys, has a large amount of unmodeled dry friction. This robustness issue is normally addressed by splitting the control task into a feedforward-like part that handles the dynamical couplings and a feedback term that enforces the tracking of the reference values stemming from the feedforward motion planning algorithm. In contrast, this thesis proposes to combine these two mechanisms, resulting in what will be called the jet-scheduling controller. Classically, the flatness property guarantees the construction of a feedforward input based on a planned motion of the flat outputs by simply combining values of the flat outputs and their time derivatives, i.e. without having to integrate differential equations. Therefore, in the absence of perturbation, this mechanism is sufficient to move the system from one state to another, once a trajectory compatible with the initial and final positions has been designed. However, when the system has some unmodeled dynamics, an additional mechanism must be provided to make sure that the planned trajectory is indeed tracked accurately. The point of view adopted in this thesis is that, instead of specifying a trajectory to be tracked explicitly, a dynamical system called "the jet scheduler" provides the derivatives (the jets) of an ideal stabilizing trajectory. These jets are updated regularly according to measurements so as to react to unknown perturbations. The flat correspondence is used to provide the values of the jets, and a subsidiary controller is designed to ensure that these jets are really matched asymptotically by the true system. Unfortunately, each of these mechanisms could possibly break the equivalence between the original nonlinear system and the linear extended system (contrary to the classical feedback linearization approach for which this correspondence is guaranteed at every time instant). The design of the jet-scheduling controllers and the implication of the possible loss of correspondence are detailed in this work. In addition, stability issues are addressed. Applications to two classes of systems are shown, namely, nonholonomic robots and cranes. The specific properties of these systems are used to achieve a rigorous stability proof. The controller for both the nonholonomic robot and a new crane design labeled SpiderCrane that fully takes advantage of the jet-scheduling mechanism are tested on real setups. Nonlinear Control ; Flatness-based Control ; Trajectory Tracking ; Stabilization ; Nonholonomic Robot ; Crane.

EPFL2008

Jet-scheduling control for flat systems

Davide Buccieri

EPFL2008