Harel Statecharts Research Articles

FORMALIZATION OF THE TECHNOLOGICAL PROCESSES AT RAILWAY STATIONS BASED ON THE STEP-BY-STEP MODELING

Purpose. Specialized software must be used to represent the technological process using step-by-step modeling methodology. Formalizing the technological process is one of the main tasks in the design or optimization phase of a railway station. The article proposes to develop a methodology of formalizing the technological processes based on the step-by-step modeling. Methodology. Using the methodology of stage-by-stage design, the input, internal and initial model of the railway station's operation were constructed. The input model of the proposed method is formed by the use case diagram, the statechart and activities diagrams, which are constructed using the tools of the IBM Rational Rose software. This model provides a graphoanalytic representation of the technological processes of a railway station with its visual control, which avoids time-consuming manual coding and eliminates errors. The diagrams below describe the technological process of a railway station based on hierarchical diagrams of the sequence of works of different detail degrees. Both initial and internal models are constructed using a unified UML modeling language. The methods of object-oriented design, finite state machines and system programming are used as research methods. Findings. The proposed methodology will make it possible to construct simulation models of railway stations using Harel statecharts. These models represent a hierarchically organized set of interacting finite state machines, while the complex model at each level of the hierarchy retains a simple and accessible structure. The start and finish signals generated by the state transition allow the model to be synchronized, and the use of state and signal description actions (UML extension) makes it possible to use external algorithms where the usual/automatic formalism becomes inconvenient. And the methodology implemented by means of the UML language, significantly facilitates the presentation and perception of the station model. Originality. The methodology of presenting a functional model of railway stations with the use of visual design methods has been improved. Practical value. The proposed method is intended for semigraphical representation of technological process of railway station operation, using the methodology of step-by-step modeling. Modeling on the basis of a graphical input model constructs internal and output models, as well as presents the methods for their transformations.

Situational model of technological operations for secondary metallurgy

Purpose: The aim of this study was development of a computer situational model of heat and power processes and transport operations for secondary steelmaking (SSM) to evaluate the effectiveness of the proposed SSM energy regimes and minimization the consumption of energy resources. Design/methodology/approach: For the solution of the tasks were used next methods: analytical and statistical methods of mathematical modeling; method of dynamic programming for the development of technological recommendations for energy modes on LF; Harel state charts to evaluate the effectiveness of the applied models. Findings: In order to provide rational energy regimes for SSM, it is necessary to introduce a new controlled parameter - the optimum time to start heating the melt at the ladle furnace unit (LF), which is determined by solving the dynamic programming task. The melt heating start time must be selected in such a way as to ensure that all the necessary technological operations are performed during metal processing in the LF, taking into account schedule constraints, and that the heating of the metal must be carried out with the maximum energy efficiency. Research limitations/implications: The main objective of the present study was to apply the mathematical modeling methods to ensure rational energy regimes of SSM. Practical implications: The developed situational model of technological operations for SSM will allow finding reserves to increase the productivity and quality of the process, and to evaluate the effectiveness of new technological solutions. Originality/value: To ensure an energy-efficient treatment of steel in LF, it is necessary: the time for starting the heating of the metal is chosen such that the energy efficiency of the LF, which depends on the thickness of the slag layer, is maximum at each stage; increase the power that is supplied to the heating of the melt by switching the voltage taps of the transformer as the thickness of the slag cover increases.

Repast Simphony Statecharts

Agent states and transitions between states are important abstractions in agent-based social simulation (ABSS). Although it is common to develop ad hoc implementations of state-based and transition-based agent behaviors, 'best practice' software engineering processes provide transparent and formally grounded design notations that translate directly into working implementations. Statecharts are a software engineering design methodology and an explicit visual and logical representation of the states of system components and the transitions between those states. Used in ABSS, they can clarify a model's logic and allow for efficient software engineering of complex state-based models. In addition to agent state and behavioral logic representation, visual statecharts can also be useful for monitoring agent status during a simulation, quickly conveying the underlying dynamics of complex models as a simulation evolves over time. Visual approaches include drag-and-drop editing capabilities for constructing state-based models of agent behaviors and conditions for agent state transitions. Repast Simphony is a widely used, open source, and freely accessible agent-based modeling toolkit. While it is possible for Repast Simphony users to create their own implementations of state-based agent behaviors and even create dynamic agent state visualizations, the effort involved in doing so is usually prohibitive. The new statecharts framework in Repast Simphony, a subset of Harel's statecharts, introduces software engineering practices through the use of statecharts that directly translate visual representations of agent states and behaviors into software implementations. By integrating an agent statecharts framework into Repast Simphony, we have made it easier for users at all levels to take advantage of this important modeling paradigm. Through the visual programming that statecharts afford, users can effectively create the software underlying agents and agent-based models. This paper describes the development and use of the free and open source Repast Simphony statecharts capability for developing ABSS models.

Bridging the Semantic Sensor Web and Multimodal Human-Machine Interaction Using SCXML

This paper presents a novel approach to combine, process and enrich data from heterogeneous sensor networks, and, further, to semantically annotate the observations of the sensed world thus obtained and publish them on the future Semantic Sensor Web. The processing and systematic annotation of sensor data of diverse nature obtained from an ever growing number of different sources that are beginning to shape the Sensor Web is a challenging endeavour. Nevertheless, a similar challenge is inherent to the activity of Human-Machine Interface designers. In this field the SCXML language, based on the concept of Harel statecharts, is being proposed by the W3C as a central element in the design of multimodal interaction managers, which have to deal with information in different communication modalities, integrating and interpreting the user’s input, and coordinating the output among them. We propose extending the use of SCXML to deal also with sensor information, as this language has the capability to combine and process this information as it does with interaction information. SCXML can also coordinate external tools (based on RDF, OGC-SWE’s O&M and OWL) to generate semantic annotations of the knowledge obtained, shareable across applications. This approach can pave the way to develop rich context-aware applications. We illustrate the discussion with a smart-car scenario that we have developed, and present the main implementation details. Keywords: Sensor web, semantic sensor web, human-machine interaction, SCXML, sensor processing, information enrichment, semantic annotation, RDF, Sensor and Actuator Networks (SANs), Internet-of-Things (IoT)

Type Theory and Language Constructs for Objects with States

In current class-based Object-Oriented Programming Languages (OOPLs), object types include only static features. How to add object dynamic behaviors modeled by Harel's statecharts into object types is a challenging task. We propose adding states and state transitions, which are largely unstated in object type theory, into object type definitions and typing rules. We argue that dynamic behaviors of objects should be part of object type definitions. We propose our type theory, the τ-calculus, which refines Abadi and Cardelli's ζ-calculus, in modeling objects with their dynamic behaviors. In our proposed type theory, we also explain that a subtyping relation between object types should imply the inclusion of their dynamic behaviors. By adding states and state transitions into object types, we propose modifying programming language constructs for state tracking.

Semantics and Runtime Monitoring of TLCharts: Statechart Automata with Temporal Logic Conditioned Transitions

This paper describes the semi-formal semantics and a run-time monitoring technique for TLCharts, a visual specification language that combines the visual and intuitive appeal of non-deterministic Harel Statecharts with formal specifications written in Linear-time (Metric) Temporal Logic (LTL and MTL). We describe an automata-theoretic semantics for non-deterministic statecharts with negation and state overlapping and extend it to cater for temporally annotated transitions, thereby providing a simple automata theoretic semantics for TLCharts. We also describe a run-time monitoring technique for TLCharts.

Refinement in statechart testing

Abstract An existing statechart testing method developed by the authors allows a tester to show the equivalence of the behaviour of an implementation of some software system to its Harel statechart specification, by testing. This requires a rather large test set and satisfaction of certain requirements for both a specification and an implementation. Introduction of additional constraints permits reduction in a test set size, without weakening of the conclusions obtained by testing. This paper describes how a test set can be derived from a relatively big statechart and investigates the role of a few specific constraints in the reduction of test set size, depending on where in the system structure these constraints are used. The main contribution of the paper is a demonstration that enforcing relatively weak constraints in the right place of a system's structure makes it possible to reduce the size of a test set by many orders of magnitude. The practical use of the contribution is to help developers structure a system under construction in such a way that it is completely testable using the described testing method with few additional constraints. Copyright © 2004 John Wiley & Sons, Ltd.

Using Harel's Statecharts to Model Business Workflows

In this paper, we model business workflows using Harel’s statecharts. Mapping to statecharts allows us to systematically identify potential workflow problems. It also allows us to investigate specific properties inherent in actual business workflows. Our research focuses on three desirable properties of active database systems — termination, confluence, and observable determinism. For termination and confluence, we develop algorithms to provide a theoretical lens linking desirable active database system properties to workflow management systems problems. We initially validate our algorithms by mapping business workflows from a case study. Our research thus builds preliminary theory by developing a systematic method for identifying workflow problems.

Towards a Model Theory for Esterel

Esterel is a synchronous language for reactive-systems design and builds the core of the commercial tool Esterel Studio. This paper shows how the constructive semantics of a combinational fragment of Esterel, as presented by Berry, can be derived in a model-theoretic fashion, thus complementing the existing behavioral, operational, and circuit-based approaches to Esterel semantics. Technically, Esterel programs are read as formulas in propositional intuitionistic logic, which are interpreted over simple linear Kripke structures, referred to as Gödel valuations. Esterel reactions are then characterized as specific Gödel valuations, called response models, and it is shown that the approach is compositional in the structure of Esterel programs.The obtained results are an important step towards explaining the logic behind Esterel semantics. In addition, the intuitionistic setting advocated in this paper nicely links to Pnueli and Shalev's semantics of Harel's Statecharts, another synchronous language for reactive-systems design. This offers interesting insights into the similarities of and the differences between Esterel and Statecharts semantics.

Meta-modelling based assembly techniques for situational method engineering

Method engineering for information system development is the discipline to construct new advanced development methods from parts of existing methods, called method fragments. To achieve this objective, we need to clarify how to model the existing methods and how to assemble method fragments into new project-specific methods, so-called situational methods. Especially, to produce meaningful methods, we should impose some constraints or rules on method assembly processes. In this paper, we propose a framework for hierarchical method modelling (meta-modelling) from three orthogonal dimensions: perspectives, abstraction and granularity. According to each dimension, methods and/or method fragments are hierarchically modelled and classified. Furthermore, we present a method assembly mechanism and its formalization as a set of rules. These rules are both syntactic and semantic constraints and presented in first order predicate logic so that they can play an important role in the assembly process of syntactically and semantically meaningful methods from existing method fragments. The benefit of our technique is illustrated by an example of method assembly, namely the integration of the Object Model and Harel's Statechart into Objectcharts.

Use of statecharts in the modelling of dynamic behaviour in the ATLAS DAQ prototype-1

Many applications within the ATLAS DAQ prototype-1 system have complicated dynamic behaviour which can be successfully modelled in terms of states and transitions between states. Previously, state diagrams implemented as finite-state machines have been used. Although effective, they become ungainly as system size increases. Harel statecharts address this problem by implementing additional features such as hierarchy and concurrency. The CHSM object-oriented language system is freeware which implements Harel statecharts as concurrent, hierarchical, finite-state machines (CHSMs). An evaluation of this language system by the ATLAS DAQ group has shown it to be suitable for describing the dynamic behaviour of typical DAQ applications. The language is currently being used to model the dynamic behaviour of the prototype-1 run-control system. The design is specified by means of a CHSM description file, and C++ code is obtained by running the CHSM compiler on the file. In parallel with the modelling work, a code generator has been developed which translates statecharts, drawn using the StP CASE tool, into the CHSM language. C++ code, describing the dynamic behaviour of the run-control system, has been successfully generated directly from StP statecharts using the CHSM generator and compiler. The validity of the design was tested using the simulation features of the Statemate CASE tool.

Software technologies for a prototype ATLAS DAQ

The ATLAS collaboration has defined a set of user requirements for the back-end software subsystem within the context of the data acquisition and event filter prototype “−1” project. Based on these requirements, a number of evaluations have been performed on candidate technologies and techniques in the areas of configuration data storage (Objectivity ODBMS; Rogue Wave Tools.h++ for C++ object persistence), inter-process communication (Corba; MPI), dynamic object behaviour (Harel StateChart generator), graphical user interfaces (cross-platform GUI builder; Java AWT) and software integration (ACE operating-system interface). This paper describes the important requirements which lead to the selection of these technologies, the results obtained from the evaluations and how we intend to apply them to the design and implementation phases of the project.

仕様の状態遷移図記述による組込みソフトウェア開発手法

Concerning the development of firmware, important problems include reducing the number of processes and the periods for testing and validation while preserving quality and reducing the overall time taken for product development. To solve these problems, one effective approach is to reduce the number of design iterations by ensuring adequate drawing up, review and validation of product specifications at an early stage of the design. One method of doing this is to write formal descriptions of the specifications for review and validation. An approach frequently adopted is to use Harel Statecharts as suggested in the OMT (Object Modeling Technique) method. However, design methods that address directly the conditions in Harel diagrams have yet to be established. The article proposes a design method that addresses the control conditions affecting basic product operations. It consists of describing the conditions that affect the entire product as a combination of basic operations, and to describe controls with reference to these basic operations. Furthermore, we propose that by using simulations of the Statecharts so created, practical actuators should be directly controlled to create a validation environment for the specifications.We have applied the proposed method to the development of control software to be built into prototype air-conditioning equipment. The preparation of the Statecharts for the prototype equipment demonstrated the effectiveness of this approach.

A multi-formalisms approach for codesign in the development of avionics

This paper presents a new approach in the development of avionics at AEROSPATIALE. The approach is based on a selective use of specification languages. Its aim is to compose partial avionics specifications in a unified format which is used for later concurrent hardware/software design steps. A demonstrator of the approach is currently in progress. It deals with the re-design of an avionics on-board system that belongs to the family of AIRBUS A340. The multi-languages specification is achieved through three graphical specification languages: Harel's StateCharts, SDL and SAO. The status of work and future perspectives are outlined.

Using Harel statecharts to model object-oriented behavior

Object-oriented analysis and design methods are increasingly being considered for complex system development. However, object-oriented implementations can introduce run-time inefficiencies. Therefore, predicting system behavior is an important simulation objective for validating completeness and analyzing performance. There are two contributors to system behavior - the individual behavior of each object and the collaborative behavior of object when executing scenarios required by the system. Modeling the collaborative interaction of objects is the primary subject of this paper. Templates for three types of objects are presented: Director, Agent and Server object classes. The mechanisms presented in this paper utilize Harel state diagram notation as supported by the Statemate CASE tool.

Stimulus-response machines

This paper describes Stimulus-Response (S-R) Machines, a new visual formalism based on the semantics of Ada. S-R Machines are SCOOP-3's [2] main medium for specifying and implementing critical units of behavior. They have the same motivation as Harel's Statecharts [3]: to manage the unstructured explosion of blobs and arrows that occur on complex State Transition Diagrams. S-R Machines add to Ada's semantics a named off-page abstraction mechanism called "boxes." Boxes are used to decompose S-R Machines into hierarchies of states (goals, steps, conditions, or modes), each of which can be easily verified. S-R Machines are similar to Harlan Mills' Box-Structured Systems [4]: our interfaces are identical to his black boxes; our bodies are similar to his state and clear boxes. Because S-R Machines combine the familiar features of dataflow diagrams, object-message diagrams, and structured flowcharts, its notation is easy to learn. S-R Machines are useful when developing state-rich safety-critical systems or whenever understanding or communication are problematical or critical (e.g., educational settings and software inspections).

Graphical specification of object oriented systems

The graphical notation Objectcharts, introduced in this paper, allows a developer to precisely specify the behaviour of object classes and to reason about the behaviour of particular configurations of objects. Objectcharts combine object oriented analysis and design techniques and Harel's statecharts to give a diagrammatic specification technique for object oriented systems.