Elena Ratto

Dealing with different time granularities in formal specifications of real-time systems

The article presents a formalization of the notion of time granularity within a logical language for specifying real-time systems. It provides the specifier with the ability of dealing with different time granularities within a single specification. That is, it allows the specifier to describe the behavior and the properties of a system and its environment with respect to different time scales and to switch among them in a suitable way. The extended logical formalism is then embedded in an object oriented structure that enhances both the expressive power and the executability of the specification language. With regard to expressiveness, it enables one to subdivide a single specification of the system and its environment into different part and to provide a number of specifications of them at different levels of abstraction, each one referring to a different time granularity. With regard to executability, it allows one to verify the consistency and the adequacy of specifications at each step of their incremental development. It also suggests an enlargement of the notions of verification and validation that takes into account the stratified structure of the object oriented specifications.

Dealing with different time scales in formal specifications

The authors motivate the need for allowing the consistent treatment of different time scales in formal specifications of time critical systems, with the purpose of enhancing the naturalness and practical usability of the notation. The approach to this issue is illustrated on TRIO, a temporal logic language for the specification of real-time systems. The authors briefly introduce TRIO and define an extension to the language which considers a temporal universe composed of various temporal domains of different time granularity. The semantics of the extended language is defined via translation mechanisms which allow one to interpret formulas referring to a larger time granularity in a finer temporal domain, and the main properties of such translations are discussed. Finally, a complete simple example of a system specified at various levels of granularity is presented.<<ETX>>

TRIO, a logic formalism for the specification of real-time systems

Results are presented of a research project aimed at the definition of an executable logic formalism for the specification of real-time systems. The logic language TRIO allows the specifier to express formally and quantitatively the temporal properties of the specified systems. A formal definition of execution of specifications in terms of generation of interpretations for the corresponding formulas is given. Also given are the conditions and degrees of generality in which such execution is possible. A specification environment based on the TRIO formalism is outlined.<<ETX>>

Embedding time granularity in logical specifications of real-time systems

The paper extends the TRIO logical specification formalism with the notion of time granularity. Such an extension provides the specifier with the ability of dealing with different time granularities within a single specification. It allows one to maintain the description of the dynamics of processes that evolve according to different time constants as separate as possible. It also makes it possible to model the dynamics of a given process with respect to different time scales. The paper first introduces time granularity in a completely general way, that is, it defines the weakest semantics of time granularity. Then a number of possible specializations of such a semantics taking into account both common-sense and domain-specific knowledge are identified. They result in a taxonomic classification of predicates that makes the formalism more expressive and easier to use.<<ETX>>

SImulation of High-Voltage Substations on Parallel ARchitectures

New generation of real-time and safety critical embedded control systems is characterized by new functionality, such as self diagnosis and system reconfiguration, that need powerful hardware architectures in order to meet performance requirements. The availability of parallel architectures based on inexpensive microprocessors suggests the adoptionof parallel computer systems even in such a critical field. In spite of that, the introduction of High Performance Computing (HPC) solutions in an industrial environment requires a careful analysis of their impact based on realistic experiments. One of such experiments is the objective of SISPAR (Simulation of high-voltage Substations on Parallel Architectures) projectL This project is aimed at evaluating the effectiveness of closely coupled parallel architectures to improve an existing application provided by ENEL, the Italian electricity utility. In particular, the project intends to parallelize a real time simulator of High Voltage (HV) electrical substations. HV-substations are nodes of the high voltage (380-220 kV) transport meshed network that links distribution network to power generation plants, located in various sites of the Italian territory. Substations mainly consist of electrical components such as breakers, insulators, etc., aggregated into Functional Units (FU). Each substation includes a specific number of FUs and is characterized by specific parameters. This plant configurability is usually exploited by developing configurable software for automation systems and plant simulators. The parallel architecture selected in SISPAR -i.e. a hypercube of transputer based nodesallows the extension of this configurability to the simulator target hardware, leading to a class of systems entirely scaleable: the number of both software simulator components and hypercube nodes is defined according to the number of FUs belonging to the specific HV-substation. Real-time simulators have to support the validation of functionality and performance of HV-substation automation systems before their installation on real substations, reproducing the same cyclic behavior, timing and I/O of such plants. The current generation of HV-substation simulators is based on conventional architectures composed of single processors, that cannot fully support the whole performance requirements. Therefore, these simulators are used to validate plant automation functions in multi-steps approach: different subsets of the substation components are simulated at each simulation session in order to meet real-time requirements.

A methodology for an incremental, logical specification of real-time systems

A methodology for an incremental, logical specification of real-time systems which is based on an object-oriented extension of a logical specification formalism is presented. Such an object-oriented framework makes available primitives for identifying, partitioning, and structuring the elements of a specification. In such a way it supports a twofold modality of dealing with abstraction, i.e. specialization and decomposition, that provides a guideline for specifications development. In particular, it provides the specifier with the ability to deal with different time granularities within a single specification. That is, it allows the specifier to describe the behavior and the properties of a system and its environment with respect to different time scales, and to switch among them in a suitable way. It also allows an extension of temporal verification and validation of specifications taking into account the incremental development and the resulting layered structure of specifications.<<ETX>>

Temporal Logic for Validation and Verifying Enel Control Systems

Abstract this paper describes the experience gained in developing and applying TRIO framework, a formal method based on metric temporal logic and a set of tools, to the specification, validation, verification, and acceptance testing of ENEL applications in the field of supervision and control systems. The paper offers an evaluation of TRIO impact experimented in ENEL industrial projects.

SPECIFYING INDUSTRIAL REAL-TIME SYSTEMS WITH A TEMPORAL LOGIC FRAMEWORK

This paper presents the TRIO logical framework to specify industrial real-time systems. Typical specification requirements for this kind of system are discussed and related to corresponding feature...