The time-triggered architecture (TTA) provides a computing infrastructure for the design and implementation of dependable distributed embedded systems. A large real-time application is decomposed into nearly autonomous clusters and nodes, and a fault-tolerant global time base of known precision is generated at every node. In the TTA, this global time is used to precisely specify the interfaces among the nodes, to simplify the communication and agreement protocols, to perform prompt error detection, and to guarantee the timeliness of real-time applications. The TTA supports a two-phased design methodology, architecture design, and component design. During the architecture design phase, the interactions among the distributed components and the interfaces of the components are fully specified in the value domain and in the temporal domain. In the succeeding component implementation phase, the components are built, taking these interface specifications as constraints. This two-phased design methodology is a prerequisite for the composability of applications implemented in the TTA and for the reuse of prevalidated components within the TTA. This paper presents the architecture model of the TTA, explains the design rationale, discusses the time-triggered communication protocols TTP/C and TTP/A, and illustrates how transparent fault tolerance can be implemented in the TTA.

this article will expedite this mapping, letting software engineers exploit the vast amounts of knowledge and experience accumulated in control theory.

Bounded rationality has been an important theme throughout the history of the theory of organizations, because it explains the sharing of information processing tasks and the existence of administrative staffs that coordinate large organizations. This article broadly surveys the theories of organizations that model such bounded rationality and decentralized information processing.

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This paper deals with the issue of consistent symbolic (qualitative) representation of continuous dynamic systems. Consistency means here that the results of reasoning with the qualitative representation hold in the underlying (quantitative) dynamic system. In the formalization proposed in this paper, the quantitative structure is represented using the notion of a general dynamic system (GDS). The qualitative counterpart (QDS), is represented by a finite-state automaton structure. The two representational substructures are related through functions, called qualitative abstractions of dynamic systems. Qualitative abstractions associate inputs, states and outputs of the QDS with partitions of appropriate GDS spaces. The paper shows how to establish such consistent partitions, given a partitioning of the system's output. To represent borders of these partitions, the notion of critical hypersurfaces is introduced. One of the main ideas that provides consistency is the interpretation of qu...

It is natural to advance closures as "atomic" processes of universal evolution, and to analyze this concept specifically. While real complex systems like organisms and complex mechanisms cannot exist at either extreme of complete closure or lack of closure, nevertheless we should consider the properties of closures in general: the introduction of boundaries; a corresponding stability; the establishment of system autonomy and identity; and thereby the introduction of emergent new systems of potentially new types. Our focus should move from simple physical closure of common objects and classical self-organizing systems to semiotically closed systems which maintain cyclic relations of perception, interpretation, decision, and action with their environments. Thus issues arise concerning the use and interpretation of symbols, representations, and/or internal models (whether explicit or implicit) by the system; and the syntactic, semantic, and pragmatic relations among the sign tok...

The goal of the research presented in this paper was to study a new software paradigm -- adaptive software -- in which the structure of an adaptive program is patterned upon the structure of an adaptive controller. Towards this aim, we implemented a domain-specific (object/target recognition) program (RAACR) that can adapt to changes in software requirements through the incorporation of feedback. RAACR is a hierarchy of domains (blackboards). Each domain includes multiple knowledge sources (KSs) and a domain scheduler. In response to feedback, knowledge sources change their processing parameters, while domain schedulers change the scheduling policy of the knowledge sources. A generic communication mechanism is implemented on the CORBA compliant SPRING operating system. The adaptability of the program is evaluated quantitatively using a requirements volatility measure and the probability of correct recognition. 1 Introduction In object/target recognition applications, it is difficult...

General Systems Logical Theory is based on the input-output systems paradigm. The language of this theory is now formalized within a categorical framework to create a new hierarchical structure of systems by n-dimensional commutative diagrams. The power of the language is illustrated by the increased expressiveness it provides for categorical concepts themselves.

We provide a conceptual analysis of ideas and prin cz les from the systems theory disc ourse whic h underlie Pattee's semantic or semiotic c losure, whic h is itself foundational for a sc hool of theoretic" biology derived from systems theory andc ybernetic , and is now being related to biologicz semiotic and explic2qL in the relational biologico sc hool of Rashevsky and Rosen. Atomic c trol systems and models are desc ribed as thec anonic" forms of semiotic organization, sharing measurement relations, but di#ering topologic)z: in that cz trol systems arec ir c larly and models linearly related to their environments. Computation inc ontrol systems is introduc2 , motivating hierarc hic al dec omposition, hybrid modeling andc ontrol systems, and antic ipatory or model-basedc ontrol. The semiotic relations inc omplex cz trol systems are des c ibed in terms of relationalc onstraints, and rules and laws are distinguished as cz tingent and nec" sary func tional entailments respecqq ely. Finally, selec)Lz as a meta-level of cz straint is introduc" as the nec6 saryc8 dition for semantic relations in control systems and models.

This paper is concerned with building large distributed real-time systems out of computational components that interact by the exchange of messages across linking interfaces (LIFs). The notions of an operational and a meta-level specification of a LIF of a component are introduced