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27
A Relational Model of NonDeterministic Dataflow
 In CONCUR'98, volume 1466 of LNCS
, 1998
"... . We recast dataflow in a modern categorical light using profunctors as a generalisation of relations. The well known causal anomalies associated with relational semantics of indeterminate dataflow are avoided, but still we preserve much of the intuitions of a relational model. The development fits ..."
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Cited by 28 (13 self)
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. We recast dataflow in a modern categorical light using profunctors as a generalisation of relations. The well known causal anomalies associated with relational semantics of indeterminate dataflow are avoided, but still we preserve much of the intuitions of a relational model. The development fits with the view of categories of models for concurrency and the general treatment of bisimulation they provide. In particular it fits with the recent categorical formulation of feedback using traced monoidal categories. The payoffs are: (1) explicit relations to existing models and semantics, especially the usual axioms of monotone IO automata are read off from the definition of profunctors, (2) a new definition of bisimulation for dataflow, the proof of the congruence of which benefits from the preservation properties associated with open maps and (3) a treatment of higherorder dataflow as a biproduct, essentially by following the geometry of interaction programme. 1 Introduction A fundament...
The expressive power of indeterminate dataflow primitives
 Information and Computation
, 1992
"... We analyze the relative expressive power of variants of the indeterminate fair merge operator in the context of static dataflow. We establish that there are three different, provably inequivalent, forms of unbounded indeterminacy. In particular, we show that the wellknown fair merge primitive canno ..."
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Cited by 17 (7 self)
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We analyze the relative expressive power of variants of the indeterminate fair merge operator in the context of static dataflow. We establish that there are three different, provably inequivalent, forms of unbounded indeterminacy. In particular, we show that the wellknown fair merge primitive cannot be expressed with just unbounded indeterminacy. Our proofs are based on a simple trace semantics and on identifying properties of the behaviors of networks that are invariant under network composition. The properties we consider in this paper are all generalizations of monotonicity. 1
Relational Semantics of NonDeterministic Dataflow
, 1997
"... We recast dataflow in a modern categorical light using profunctors as a generalization of relations. The well known causal anomalies associated with relational semantics of indeterminate dataflow are avoided, but still we preserve much of the intuitions of a relational model. The development fit ..."
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Cited by 12 (5 self)
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We recast dataflow in a modern categorical light using profunctors as a generalization of relations. The well known causal anomalies associated with relational semantics of indeterminate dataflow are avoided, but still we preserve much of the intuitions of a relational model. The development fits with the view of categories of models for concurrency and the general treatment of bisimulation they provide. In particular it fits with the recent categorical formulation of feedback using traced monoidal categories. The payoffs are: (1) explicit relations to existing models and semantics, especially the usual axioms of monotone IO automata are read off from the definition of profunctors, (2) a new definition of bisimulation for dataflow, the proof of the congruence of which benefits from the preservation properties associated with open maps and (3) a treatment of higherorder dataflow as a biproduct, essentially by following the geometry of interaction programme.
Separating concurrent languages with categories of language embeddings
 In Proceedings of the 23 rd Annual ACM Symposium on Theory of Computing
, 1991
"... Concurrent programming enjoys a proliferation of languages but suffers from the lack of a general method of language comparison. In particular, concurrent (as well as sequential) programming languages cannot be usefully distinguished based on complexitytheoretic considerations, since most of them ..."
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Cited by 12 (1 self)
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Concurrent programming enjoys a proliferation of languages but suffers from the lack of a general method of language comparison. In particular, concurrent (as well as sequential) programming languages cannot be usefully distinguished based on complexitytheoretic considerations, since most of them are Turingcomplete. Nevertheless, differences between programming languages matter, else we would not have invented so many of them. We develop a general method for comparing concurrent programming languages based on their algebraic (structural) complexity, and, using this method, achieve separation results among many wellknown concurrent languages. The method is not restricted to concurrent languages. It can be used to compare the algebraic complexity of abstract machine models, other families of programming languages, logics, and, more generaly, any family of languages with some syntactic operations and a notion of semantic equivalence. The method can also be used to compare the algebraic complexity of families of operations wit hin a language or across languages. We note that using the method we were able to compare languages and computational models that do not have a common semantic basis.
Branching vs. linear time – semantical perspective
 In Proc. 5th Int’l Symp. on ATVA, LNCS 4762
"... Abstract. The discussion in the computerscience literature of the relative merits of linear versus branchingtime frameworks goes back to early 1980s. One of the beliefs dominating this discussion has been that the lineartime framework is not expressive enough semantically, making lineartime log ..."
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Cited by 12 (2 self)
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Abstract. The discussion in the computerscience literature of the relative merits of linear versus branchingtime frameworks goes back to early 1980s. One of the beliefs dominating this discussion has been that the lineartime framework is not expressive enough semantically, making lineartime logics lacking in expressiveness. In this work we examine the branchinglinear issue from the perspective of process equivalence, which is one of the most fundamental notions in concurrency theory, as defining a notion of process equivalence essentially amounts to defining semantics for processes. Over the last three decades numerous notions of process equivalence have been proposed. Researchers in this area do not anymore try to identify the “right ” notion of equivalence. Rather, focus has shifted to providing taxonomic frameworks, such as “the linearbranching spectrum”, for the many proposed notions and trying to determine suitability for different applications. We revisit this issue here from a fresh perspective. We postulate three principles that we view as fundamental to any discussion of process equivalence. First, we borrow from research in denotational semantics and take contextual equivalence as the primary notion of equivalence. This eliminates many testing scenarios as either too strong or too weak. Second, we require the description of a process to fully specify all relevant behavioral aspects of the process. Finally, we require observable process behavior to be reflected in its input/output behavior. Under these postulates the distinctions between the linear and branching semantics tend to evaporate. As an example, we apply these principles to the framework of transducers, a classical notion of statebased processes that dates back to the 1950s and is well suited to hardware modeling. We show that our postulates result in a unique notion of process equivalence, which is trace based, rather than tree based. 1
A Domaintheoretic Model for a Higherorder Process Calculus
 Proceedings of the 17th International Colloquium on Automata Languages and Programming
, 1996
"... In this paper we study a higherorder process calculus, a restriction of one due to Boudol, and develop an abstract, model for it. By abstract we mean that the model is constructed domaintheoretically and reflects a certain conceptual viewpoint about observability. It is not constructed from the sy ..."
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Cited by 10 (2 self)
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In this paper we study a higherorder process calculus, a restriction of one due to Boudol, and develop an abstract, model for it. By abstract we mean that the model is constructed domaintheoretically and reflects a certain conceptual viewpoint about observability. It is not constructed from the syntax of the calculus or from computation sequences. We describe a new powerdomain construction that can be given additional algebraic structure that allows one to model concurrent composition, in the same sense that Plotkin's powerdomain can have a continuous binary operation defined on it to model choice. We show that the model constructed this way is adequate with respect to the operational semantics. The model that we develop and our analysis of it is closely related to the work of Abramsky and Ong on the lazy lambda calculus. 1 Introduction A fundamental problem in the semantics of parallel programming languages is integrating concurrency with abstraction. Kahn's pioneering work on stat...
A Simple Generalization of Kahn's Principle to Indeterminate Dataflow Networks
 Semantics for Concurrency, Leicester
, 1990
"... Kahn's principle states that if each process in a dataflow network computes a continuous input/output function, then so does the entire network. Moreover, in that case the function computed by the network is the least fixed point of a continuous functional determined by the structure of the network ..."
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Cited by 8 (2 self)
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Kahn's principle states that if each process in a dataflow network computes a continuous input/output function, then so does the entire network. Moreover, in that case the function computed by the network is the least fixed point of a continuous functional determined by the structure of the network and the functions computed by the individual processes. Previous attempts to generalize this principle in a straightforward way to "indeterminate" networks, in which processes need not compute functions, have been either too complex or have failed to give results consistent with operational semantics. In this paper, we give a simple, direct generalization of Kahn's fixedpoint principle to a large class of indeterminate dataflow networks, and we prove that results obtained by the generalized principle are in agreement with a natural operational semantics. 1 Introduction Dataflow networks are a parallel programming paradigm in which a collection of concurrently and asynchronously executing s...
Arithmetic + Logic + Geometry = Concurrency
 In Proc. First Latin American Symposium on Theoretical Informatics, LNCS 583
, 1992
"... This paper ties together three primitivist views of concurrency whose development the author has had some involvement with, namely the arithmetic of schedules, the logic of scheduleautomaton duality, and the geometry of automata. Separately each of these views shed considerable light on concurrency ..."
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Cited by 7 (3 self)
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This paper ties together three primitivist views of concurrency whose development the author has had some involvement with, namely the arithmetic of schedules, the logic of scheduleautomaton duality, and the geometry of automata. Separately each of these views shed considerable light on concurrency. Our goal here is to bring these three views together coherently in the one place. The general picture is as follows. 1 2 3 Arithmetic of Schedules
A Compositional Model for Confluent Dynamic DataFlow Networks
, 2000
"... . We introduce a statebased language for programming dynamically changing networks which consist of processes that communicate asynchronously. For this language we introduce an operational semantics and a notion of observable which includes both partial correctness and absence of deadlock. Our ..."
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Cited by 6 (2 self)
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. We introduce a statebased language for programming dynamically changing networks which consist of processes that communicate asynchronously. For this language we introduce an operational semantics and a notion of observable which includes both partial correctness and absence of deadlock. Our main result is a compositional characterization of this notion of observable for a confluent sublanguage. 1 Introduction The goal of this paper is to develop a compositional semantics of a confluent subset of the language MaC (Mobile asynchronous Channels). MaC is an imperative programming language for describing the behavior of dynamic networks of asynchronously communicating processes. A program in MaC consists of a (finite) number of generic process descriptions. Processes can be created dynamically and have an independent activity that proceeds in parallel with all the other processes in the system. They possess some internal data, which they store in variables. The value of a varia...
Compositionality in synchronous data flow: Modular code generation from hierarchical sdf graphs
, 2010
"... Hierarchical SDF models are not compositional: a composite SDF actor cannot be represented as an atomic SDF actor without loss of information that can lead to rate inconsistency or deadlock. Motivated by the need for incremental and modular code generation from hierarchical SDF models, we introduce ..."
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Cited by 6 (5 self)
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Hierarchical SDF models are not compositional: a composite SDF actor cannot be represented as an atomic SDF actor without loss of information that can lead to rate inconsistency or deadlock. Motivated by the need for incremental and modular code generation from hierarchical SDF models, we introduce in this paper DSSF profiles. DSSF (Deterministic SDF with Shared FIFOs) forms a compositional abstraction of composite actors that can be used for modular compilation. We provide algorithms for automatic synthesis of nonmonolithic DSSF profiles of composite actors given DSSF profiles of their subactors. We show how different tradeoffs can be explored when synthesizing such profiles, in terms of modularity (keeping the size of the generated DSSF profile small) versus reusability (maintaining necessary information to preserve rate consistency and deadlockabsence) as well as algorithmic complexity. We show that our method guarantees maximal reusability and report on a prototype implementation. 1