Lightweight Time Modeling in Timed Creol

An Open System Operational Semantics for an Object-Oriented and Component-Based Language

Many long-lived and distributed systems must remain available yet evolve over time, due to, e.g., bugfixes, feature extensions, or changing user requirements. To facilitate such changes, formal methods can help in modeling and analyzing runtime software evolution. This paper presents an executable object-oriented modeling language which supports runtime software evolution. The language, based on Creol, targets distributed systems by active objects, asynchronous method calls, and futures. A dynamic class construct is proposed in this setting, providing an asynchronous and modular upgrade mechanism. At runtime, class redefinitions gradually upgrade existing instances of a class and of its subclasses. An upgrade may depend on previous upgrades of other classes. For asynchronous runtime upgrades, the static picture may differ from the actual runtime system. An operational semantics and a type and effect system are given for the language. The type analysis of an upgrade infers and collects dependencies on previous upgrades. These dependencies are exploited as runtime constraints to ensure type safety.KeywordsType SystemOperational SemanticClass ConstraintTyping EnvironmentStage NumberThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In the concurrent objects model, objects have conceptually dedicated processors and live in a distributed environment with unordered communication by means of asynchronous method calls. Method callers may decide at runtime when to synchronize with the reply from a call. This paper presents a CLP-based approach to symbolic execution of concurrent OO programs. Developing a symbolic execution engine for concurrent objects is challenging because it needs to combine the OO features of the language, concurrency and backtracking. Our approach consists in, first, transforming the OO program into an equivalent CLP program which contains calls to specific builtins that handle the concurrency model. The builtins are implemented in CLP and include primitives to handle asynchronous calls synchronization operations and scheduling policies, among others. Interestingly, symbolic execution of the transformed programs then relies simply on the standard sequential execution of CLP. We report on a prototype implementation within the PET system which shows the feasibility of our approach.KeywordsSchedule PolicyGlobal StateConcurrent ProgramSymbolic ExecutionFuture VariableThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

In this paper we investigate the addition of first-class relationships to a prototypical object-oriented programming language (a “middleweight” fragment of Java). We provide language-level constructs to declare relationships between classes and to manipulate relationship instances. We allow relationships to have attributes and provide a novel notion of relationship inheritance. We formalize our language giving both the type system and operational semantics and prove certain key safety properties.KeywordsOperational SemanticType SoundnessMethod BodyRelationship InheritanceSubject ReductionThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

An important issue when defining a rule-based agent programming language is the design of interpreters for these programming languages. Since these languages are all based on some notion of rule, an interpreter must provide some means of selection from a set of such rules. We provide a concrete and intuitive ordering on rules on which this selection can be based. This ordering is inspired by the common sense metaphor of intelligent agents in Artificial Intelligence. Furthermore, we provide a language with a formal semantics for programming agent interpreters. The main idea is not to integrate this language into the agent language itself, but to provide the constructs for building interpreters at another (meta) level of specification. The operational semantics is accordingly specified at the meta level, by means of a (meta) transition system. Using this language we make a comparison between several interpreters for agent languages in the literature.

Cyber-physical systems (CPSs) integrate continuous behavior of a physical controlled plant with discrete behavior provided by a controlling cyber (software) part. The integration is challenging because continuous, Newtonian time of the physical part needs be reconciled with discrete time of the cyber part. In this work, the event-based asynchronous actors of Theatre extended with continuous modes, are used for modelling and analyzing CPSs. Continuous modes capture the dynamic laws (ODEs) of variation of physical/environmental variables. Theatre is control-based and distributed. It is implemented in Java, which is used both as the modelling language and as the target implementation language. Specific control forms were developed for simulating a distributed CPS and for assessing its functional/temporal behavior. Continuous modes exploit suitable ODE solvers to predict the future values of selected variables at specific time points. Although classical actors depend on non-deterministic message passing, a Theatre model can be designed to have a deterministic behavior. A hybrid Theatre model can be analyzed by exhaustive model checking by having, for instance, that the computations of the ODE solvers are, preliminarily, offline collected and reused during verification. This paper describes Theatre, summarizes its operational semantics and illustrates a model reduction onto Uppaal timed automata. Then an automotive deterministic model based on both wired and Controller Area Network transmitted messages is presented and thoroughly analysed.

Modeling of Process Control Systems in Omola

This paper presents a JAVA based framework for RTL modeling and simulation of digital hardware designs. After linking between object-oriented concepts and RTL models, the JAVA analogy to features found in a widely used hardware description language like Verilog is laid down. While focusing primarily on synchronous designs and cycle based simulation, the way to broaden this scope to event driven simulation is pointed out. Using a general object-oriented programming language for RTL modeling and simulation paves way for a more seamless software and hardware integration of a typical digital system.

The proper and comprehensive identification of systemlevel failure mode during risk assessment for space systems has difficulty due to the complexity of system-level interactions that involve multi-physics and dynamic phenomena. This study looks into system-level potential failure mode identification by using a system-level modeling and simulation-based approach to risk assessment for space systems. The proposed approach is based on utilization of the modeling language “Modelica”, an equation-based, objectoriented modeling language that allows acausal modeling for complex cyber-physical systems. The Modelica has an important modeling capability for system-level interactions that involve multi-physics phenomena. This paper discusses the technical feasibility and expected effect of this approach based on several trial results of the proposed approach. Furthermore, this paper presents several issues with this approach as future work subjects.

Object-oriented modeling has become the de-facto standard in the software development process during the last decades. A great deal of research in this area focuses on proposing modeling languages. In order to properly understand, and assess an object oriented modeling language, we believe that a set of criteria or requirements is needed. This paper presents a framework to investigate and compare graphical object oriented modeling languages. This framework is based on a requirement set for an ideal object-oriented modeling languages.

Modelling concurrent objects running on the TSO and ARMv8 memory models

ISO 10303 is the set of standards that define the Product Data Exchange using STEP or PDES. Part 11 of the standard is the EXPRESS modelling language, an objectoriented modelling language upon which the application protocols for data exchange are based. To display and analyse EXPRESS schema, ISO10303 contains a graphical depiction of a subset of EXPRESS, termed EXPRESS-G. When using EXPRESS-G to design large schema, the authors have found it to be limited in visualizing and interpreting the schema and the implied relations between entities and types. This paper presents a graphical language for designing schema to be represented in EXPRESS. Across between EXPRESS and more traditional ER modelling approaches, Visual-EXPRESS is a more compact diagram when compared to EXPRESS-G. The specification for Visual-EXPRESS also includes the algorithm to convert the graphical schema into a legal EXPRESS schema.

I will introduce the main ideas of rewriting logic [11]—a logic for the specification, prototyping and programming of concurrent systems in which concurrent computation exactly corresponds to logical deduction—and will discuss some promising directions for its use as a logical and semantic framework for distributed computing and communication protocols. An important aspect is its wide-spectrum character. Thus, on the one hand it connects smoothly with—and provides a formal foundation for—notations suitable for the early phases of software design, such as architectural description languages and object-oriented modeling languages [14, 19]; and on the other hand it also provides a natural implementation path through subsets of the logic that are efficiently implement able as distributed or mobile languages [9]. Similarly, rewriting logic specifications, when supported by appropriate tools, can be used in a wide range of specification, prototyping, code generation, testing, formal analysis, and formal verification efforts to reach high levels of assurance about a system’s correctness. All these capabilities seem potentially useful for specifying, prototyping, testing, validating, and implementing distributed systems in general and communication protocols in particular; and they offer the promise of substantially narrowing the gap between specification and code. and of reaching high assurance about the correctness of implementations that can themselves be realized in efficient subsets of rewriting logic.KeywordsModal LogicCommunication ProtocolConcurrent SystemElectronic NoteSemantic FrameworkThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

EOOLT 2010 was the third edition of the EOOLT workshop series. The workshop is intended to bring together researchers and practitioners from-different equation-based object-oriented (EOO) modeling language communities. This year's workshop also expands the scope to include the whole design space of languages for cyber-physical systems, where physical dynamics are mixed with networks and software. The workshop gathered 31 participants to present and discuss thirteen different papers grouped into the four areas of realtime oriented modeling languages and tools, modeling language design, simulation and model compilation, and modeling and simulation tools.

Although the Unified Modeling Language (UML) is by now accepted as a standard and is widely used as an object-oriented modeling language, some languages such as Z or VDM are preferred to formally specify reference models. Here, we present a reference model for hypermedia systems in UML. It is an object-oriented and Dexter-based approach that uses UML to provide an intuitive graphical representation of the model. The class diagrams are supplemented with formal constraints in the Object Constraint Language (OCL), adding invariants on elements as well as preconditions and postconditions on operations. The result is an easily extendable reference model for describing specific hypermedia systems, for example, like adaptive or mobile systems. Our contribution shows how formal and semiformal object-oriented techniques can be integrated in the metamodeling process.