SIGNAL is a

programming language A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language. The description of a programming ...

based on synchronized data-flow (flows + synchronization): a process is a set of equations on elementary flows describing both data and control. The SIGNAL

formal model In logic, mathematics, computer science, and linguistics, a formal language consists of words whose letters are taken from an alphabet and are well-formed according to a specific set of rules. The alphabet of a formal language consists of symb ...

provides the capability to describe

systems A system is a group of interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment, is described by its boundaries, structure and purpose and express ...

with several clocks (polychronous systems) as relational specifications. Relations are useful as partial specifications and as specifications of non-deterministic devices (for instance a non-deterministic

bus A bus (contracted from omnibus, with variants multibus, motorbus, autobus, etc.) is a road vehicle that carries significantly more passengers than an average car or van. It is most commonly used in public transport, but is also in use for cha ...

) or external processes (for instance an unsafe car driver). Using SIGNAL allows one to

specify Specify (foaled 1962) was a British-bred Thoroughbred racehorse who competed in National Hunt racing and is noted for winning the 1971 Grand National. Background Specify was a bay gelding bred in Norwich, England by Alan Parker. He was initia ...

an application, to design an

architecture Architecture is the art and technique of designing and building, as distinguished from the skills associated with construction. It is both the process and the product of sketching, conceiving, planning, designing, and constructing building ...

, to refine detailed components down to

RTOS A real-time operating system (RTOS) is an operating system (OS) for real-time applications that processes data and events that have critically defined time constraints. An RTOS is distinct from a time-sharing operating system, such as Unix, which m ...

or hardware description. The SIGNAL model supports a design methodology which goes from

specification A specification often refers to a set of documented requirements to be satisfied by a material, design, product, or service. A specification is often a type of technical standard. There are different types of technical or engineering specificati ...

implementation Implementation is the realization of an application, or execution of a plan, idea, model, design, specification, standard, algorithm, or policy. Industry-specific definitions Computer science In computer science, an implementation is a realiza ...

, from

abstraction Abstraction in its main sense is a conceptual process wherein general rules and concepts are derived from the usage and classification of specific examples, literal ("real" or "concrete") signifiers, first principles, or other methods. "An abstr ...

concretization In metaphysics, the distinction between abstract and concrete refers to a divide between two types of entities. Many philosophers hold that this difference has fundamental metaphysical significance. Examples of concrete objects include plants, Hum ...

, from synchrony to asynchrony. SIGNAL has been mainly developed i
INRIA
http://www.inria.fr/en/en/teams/espresso Espresso team] since the 1980s, at the same time as similar programming languages,

Esterel Esterel is a synchronous programming language for the development of complex reactive systems. The imperative programming style of Esterel allows the simple expression of parallelism and preemption. As a consequence, it is well suited for contr ...

and

Lustre Lustre or Luster may refer to: Places * Luster, Norway, a municipality in Vestlandet, Norway ** Luster (village), a village in the municipality of Luster * Lustre, Montana, an unincorporated community in the United States Entertainment * '' ...

A brief history

The SIGNAL language was first designed for signal processing applications in the beginning of the 1980s. It has been proposed to answer the demand of new

domain-specific Domain specificity is a theoretical position in cognitive science (especially modern cognitive development) that argues that many aspects of cognition are supported by specialized, presumably evolutionarily specified, learning devices. The positi ...

language for the design of signal processing applications, adopting a

dataflow In computing, dataflow is a broad concept, which has various meanings depending on the application and context. In the context of software architecture, data flow relates to stream processing or reactive programming. Software architecture Dataf ...

and block-diagram style with

array An array is a systematic arrangement of similar objects, usually in rows and columns. Things called an array include: {{TOC right Music * In twelve-tone and serial composition, the presentation of simultaneous twelve-tone sets such that the ...

and

sliding window A sliding window protocol is a feature of packet-based data transmission protocols. Sliding window protocols are used where reliable in-order delivery of packets is required, such as in the data link layer (OSI layer 2) as well as in the Transm ...

operators. P. Le Guernic, A. Benveniste, and T. Gautier have been in charge of the language definition. The first paper on SIGNAL was published in 1982, while the first complete description of SIGNAL appeared in the PhD thesis of T. Gautier. The symbolic representation of SIGNAL via z/3z (over 1,0,1 has been introduced in 1986. A full compiler of SIGNAL based on the clock calculus on hierarchy of Boolean clocks, was described by L. Besnard in his PhD thesis in 1992. The clock calculus has been improved later by T. Amagbegnon with the proposition of arborescent canonical forms. During the 1990s, the application domain of the SIGNAL language has been extended into general embedded and real-time systems. The relation-oriented specification style enabled the increasing construction of the systems, and also led to the design considering multi-clocked systems, compared to the original single-clock-based implementation of Esterel and Lustre. Moreover, the design and implementation of distributed embedded systems were also taken into account in SIGNAL. The corresponding research includes the optimization methods proposed by B. Chéron, the clustering models defined by B. Le Goff, the abstraction and separate compilation formalized by O. Maffeïs, and the implementation of distributed programs developed by P. Aubry.

The Polychrony Toolsets

The Polychrony toolset is an open-source development environment for critical/embedded systems based on SIGNAL, a

real-time Real-time or real time describes various operations in computing or other processes that must guarantee response times within a specified time (deadline), usually a relatively short time. A real-time process is generally one that happens in defined ...

polychronous data-flow language. It provides a unified model-driven environment to perform design exploration by using top-down and bottom-up design methodologies formally supported by design model transformations from

and from synchrony to asynchrony. It can be included in

heterogeneous Homogeneity and heterogeneity are concepts often used in the sciences and statistics relating to the uniformity of a substance or organism. A material or image that is homogeneous is uniform in composition or character (i.e. color, shape, siz ...

design systems with various input formalisms and output languages. Polychrony is a set of tools composed of: * A SIGNAL batch

compiler In computing, a compiler is a computer program that translates computer code written in one programming language (the ''source'' language) into another language (the ''target'' language). The name "compiler" is primarily used for programs that ...

* A

Graphical User Interface The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, inste ...

(editor + interactive access to compiling functionalities) * Th
Sigali
tool, an associated formal system for

formal verification In the context of hardware and software systems, formal verification is the act of proving or disproving the correctness of intended algorithms underlying a system with respect to a certain formal specification or property, using formal metho ...

and controller synthesis. Sigali is developed together with th
INRIA
project.

The SME environment

The SME (SIGNAL Meta under Eclipse) environment is a front-end of Polychrony in the

Eclipse An eclipse is an astronomical event that occurs when an astronomical object or spacecraft is temporarily obscured, by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three ce ...

environment based on

Model-Driven Engineering Model-driven engineering (MDE) is a software development methodology that focuses on creating and exploiting domain models, which are conceptual models of all the topics related to a specific problem. Hence, it highlights and aims at abstract re ...

(MDE) technologies. It consists of a set of Eclipse plug-ins which rely on the

Eclipse Modeling Framework Eclipse Modeling Framework (EMF) is an Eclipse-based modeling framework and code generation facility for building tools and other applications based on a structured data model. From a model specification described in XML Metadata Interchange ...

(EMF). The environment is built around SME, a

metamodel A metamodel or surrogate model is a model of a model, and metamodeling is the process of generating such metamodels. Thus metamodeling or meta-modeling is the analysis, construction and development of the frames, rules, constraints, models and ...

of the SIGNAL language extended with mode automataJ.-P. Talpin, C. Brunette, T. Gautier, and A. Gamatié. Polychronous mode automata. Proceedings of the 6th ACM & IEEE International conference on Embedded software (EMSOFT '06), ACM Press, October 2006, 83-92. concepts. The SME environment is composed of several plug-ins which correspond to: * A reflexive editor: a

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

view allowing to manipulate models conform to the SME metamodel. * A graphical modeler based on th
TopCased
modeling facilities (cf. previous picture). * A reflexive editor and an Eclipse view to create compilation scenarios. * A direct connection to the Polychrony services (

compilation Compilation may refer to: *In computer programming, the translation of source code into object code by a compiler **Compilation error **Compilation unit *Product bundling, a marketing strategy used to sell multiple products *Compilation thesis M ...

, etc.). * A

documentation Documentation is any communicable material that is used to describe, explain or instruct regarding some attributes of an object, system or procedure, such as its parts, assembly, installation, maintenance and use. As a form of knowledge manageme ...

and model examples.

Notes and references

{{Reflist, colwidth

External links

The INRIA/IRISA Espresso team

The Polychrony toolset dedicated to SIGNAL
(official website of Polychrony)
Synchrone Lab
(the synchronous language Lustre)

(the synchronous Language Esterel) Declarative programming languages Synchronous programming languages Hardware description languages Formal methods Software modeling language

A brief history

The Polychrony Toolsets

The SME environment

See also

Notes and references

External links