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Why Interaction Is More Powerful Than Algorithms
, 1997
"... alancing operation is not uniquely determined by the operation alone, since it depends on changes of state by deposit and withdraw operations that cannot be predicted or controlled. An object's operations return results that depend on changes of state controlled by unpredictable external actions. T ..."
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Cited by 221 (17 self)
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alancing operation is not uniquely determined by the operation alone, since it depends on changes of state by deposit and withdraw operations that cannot be predicted or controlled. An object's operations return results that depend on changes of state controlled by unpredictable external actions. The growing pains of software technology are due to the fact that programming in the large is inherently interactive and cannot be expressed by or reduced to programming in the small. The behavior of airline reservation systems and other embedded systems cannot be expressed by algorithms. Fred Brooks's persuasive argument [1] that there is no silver bullet for specifying complex systems is a consequence of the irreducibility of interactive systems to algorithms. If silver bullets are interpreted as formal (or algorithmic) system specifications, the nonexistence of silver bullets can actually be proved. Artificial intelligence has undergone a paradigm shift from logicbased to interactive
On the Expressive Power of a Language for Programming Coordination Media
 In Proceedings of the 1998 ACM Symposium on Applied Computing (SAC’98
, 1998
"... A programmable coordination medium is a shared communication device whose behaviour can be defined by means of a suitable programming language according to the global system needs. This notion has indeed an impact over the design of multicomponent software system, since (part of) the system computa ..."
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Cited by 34 (24 self)
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A programmable coordination medium is a shared communication device whose behaviour can be defined by means of a suitable programming language according to the global system needs. This notion has indeed an impact over the design of multicomponent software system, since (part of) the system computational charge of can be in principle shifted from the communicating components (agents) to the communication device. At the same time, this raises the issue of the computational power of a programmable coordination medium, and of its expressiveness. As a meaningful example, this paper discusses the case of ReSpecT, the firstorder logic language used by the ACLT coordination model to define the behaviour of its multiple programmable logic tuple spaces, called tuple centres. Its expressiveness is discussed first by comparing ReSpecT with Petri Nets, taken as a reference model for the specification and design of concurrent and distributed systems, then by presenting some simple cases of coor...
Turing Machines, Transition Systems, and Interaction
 Information and Computation
, 2004
"... We present Persistent Turing Machines (PTMs), a new way of interpreting Turingmachine computation, one that is both interactive and persistent. A PTM repeatedly receives an input token from the environment, computes for a while, and then outputs the result. Moreover, it can \remember" its previo ..."
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Cited by 26 (3 self)
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We present Persistent Turing Machines (PTMs), a new way of interpreting Turingmachine computation, one that is both interactive and persistent. A PTM repeatedly receives an input token from the environment, computes for a while, and then outputs the result. Moreover, it can \remember" its previous state (worktape contents) upon commencing a new computation. We show that the class of PTMs is isomorphic to a very general class of eective transition systems, thereby allowing one to view PTMs as transition systems \in disguise." The persistent stream language (PSL) of a PTM is a coinductively dened set of interaction streams : innite sequences of pairs of the form (w i ; w o ), recording, for each interaction with the environment, the input token received by the PTM and the corresponding output token. We dene an innite hierarchy of successively ner equivalences for PTMs over nite interactionstream prexes and show that the limit of this hierarchy does not coincide with PSLequivalence. The presence of this \gap" can be attributed to the fact that the transition systems corresponding to PTM computations naturally exhibit unbounded nondeterminism. We also consider amnesic PTMs, where each new computation begins with a blank work tape, and a corresponding notion of equivalence based on amnesic stream languages (ASLs). We show that the class of ASLs is strictly contained in the class of PSLs. Amnesic stream languages are representative of the classical view of Turingmachine computation. One may consequently conclude that, in a streambased setting, the extension of the Turingmachine model with persistence is a nontrivial one, and provides a formal foundation for reasoning about programming concepts such as objects with static elds. We additional...
SelfOrganizing Manufacturing Control: An Industrial Application of Agent Technology
 In Proc. of the Fourth Int. Conf. on MultiAgent Systems, pages 87 – 94
, 2000
"... We present an auctionbased approach to manufacturing control. Workpieces auction off their current task, while machines bid for tasks. When awarding a machine, a workpiece takes into account not only the machine's current work in process, but also the outgoing flow of material. If a machine's outgo ..."
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Cited by 22 (3 self)
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We present an auctionbased approach to manufacturing control. Workpieces auction off their current task, while machines bid for tasks. When awarding a machine, a workpiece takes into account not only the machine's current work in process, but also the outgoing flow of material. If a machine's outgoing stream is blocked, eventually the machine will not accept a new workpiece, thus blocking its input stream as well. As a result a capacity bottleneck is automatically propagated in the opposite direction of the material flow. A unique feature of this mechanism is that it does not presuppose any specific material flow; the current capacity bottleneck is always propagated in the opposite direction of the actual flow, no matter what this flow looks like. This paper includes a detailed analysis of the mechanism, including a formal proof of its freedom of deadlocks. DaimlerChrysler evaluated the new control approach as a bypass to an existing manufacturing line. A suite of performance tests ...
Hypercomputation and the Physical ChurchTuring Thesis
, 2003
"... A version of the ChurchTuring Thesis states that every e#ectively realizable physical system can be defined by Turing Machines (`Thesis P'); in this formulation the Thesis appears an empirical, more than a logicomathematical, proposition. We review the main approaches to computation beyond Turing ..."
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Cited by 21 (0 self)
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A version of the ChurchTuring Thesis states that every e#ectively realizable physical system can be defined by Turing Machines (`Thesis P'); in this formulation the Thesis appears an empirical, more than a logicomathematical, proposition. We review the main approaches to computation beyond Turing definability (`hypercomputation'): supertask, nonwellfounded, analog, quantum, and retrocausal computation. These models depend on infinite computation, explicitly or implicitly, and appear physically implausible; moreover, even if infinite computation were realizable, the Halting Problem would not be a#ected. Therefore, Thesis P is not essentially di#erent from the standard ChurchTuring Thesis.
A Transition System Semantics for the ControlDriven Coordination Language MANIFOLD
 THEORETICAL COMPUTER SCIENCE
, 1998
"... Coordination languages are a new class of parallel programming languages which manage the interactions among concurrent programs. Basically, coordination is achieved either by manipulating data values shared among all active processes or by dynamically evolving the interconnections among the process ..."
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Cited by 9 (7 self)
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Coordination languages are a new class of parallel programming languages which manage the interactions among concurrent programs. Basically, coordination is achieved either by manipulating data values shared among all active processes or by dynamically evolving the interconnections among the processes as a consequence of observations of their state changes. The latter, also called controldriven coordination, is supported by MANIFOLD. We present the formal semantics of a kernel of MANIFOLD, based on a twolevel transition system model: the first level is used to specify the ideal behavior of each single component in a MANIFOLD system, whereas the second level captures their interactions. Although we apply our twolevel model in this paper to define the semantics of a controloriented coordination language, this approach is useful for the formal studies of other coordination models and languages as well.
Modeling Indirect Interaction in Open Computational Systems
 Proc. Theory and Practice of Open Computational Systems (TAPOCS
, 2003
"... Open systems are part of a paradigm shift from algorithmic to interactive computation. Multiagent systems in nature that exhibit emergent behavior and stigmergy offer inspiration for research in open systems and enabling technologies for collaboration. This contribution distinguishes two types of in ..."
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Cited by 8 (3 self)
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Open systems are part of a paradigm shift from algorithmic to interactive computation. Multiagent systems in nature that exhibit emergent behavior and stigmergy offer inspiration for research in open systems and enabling technologies for collaboration. This contribution distinguishes two types of interaction, directly via messages, and indirectly via persistent observable state changes. Models of collaboration are incomplete if they fail to explicitly represent indirect interaction; a richer set of system behaviors is possible when computational entities interact indirectly, including via analog media, such as the real world, than when interaction is exclusively direct. Indirect interaction is therefore a precondition for certain emergent behaviors.
SuperTuring or NonTuring? Extending the Concept of Computation
"... “Hypercomputation ” is often defined as transcending Turing computation in the sense of computing a larger class of functions than can Turing machines. While this possibility is important and interesting, this paper argues that there are many other important senses in which we may “transcend Turing ..."
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Cited by 8 (8 self)
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“Hypercomputation ” is often defined as transcending Turing computation in the sense of computing a larger class of functions than can Turing machines. While this possibility is important and interesting, this paper argues that there are many other important senses in which we may “transcend Turing computation. ” Turing computation, like all models, exists in a frame of relevance, which underlies the assumptions on which it rests and the questions that it is suited to answer. Although appropriate in many circumstances, there are other important applications of the idea of computation for which this model is not relevant. Therefore we should supplement it with new models based on different assumptions and suited to answering different questions. In alternative frames of relevance, including natural computation and nanocomputation, the central issues include realtime response, continuity, indeterminacy, and parallelism. Once we understand computation in a broader sense, we can see new possibilities for using physical processes to achieve computational goals, which will increase in importance as we approach the limits of electronic binary logic. Key words: hypercomputation, ChurchTuring thesis, natural computation, theory of computation, model of computation, Turing computation,
The Fundamental Limit and Origin of Complexity in Biological Systems: A New Model for the Origin of Life
"... Abstract. Generally unicellular prokaryotes are considered the most fundamental form of living system. Many researchers include viruses since they commandeer cellular machinery in their replication; while others insist viruses are merely complex infective proteins. New biological principles are intr ..."
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Cited by 7 (7 self)
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Abstract. Generally unicellular prokaryotes are considered the most fundamental form of living system. Many researchers include viruses since they commandeer cellular machinery in their replication; while others insist viruses are merely complex infective proteins. New biological principles are introduced suggesting that even the prion, the infectious protein responsible for transmissible spongiform encephalopathies, qualifies as the most fundamental form of life; and remains in general concordance with the sixpoint definition of living systems put forth by Humberto Maturana and his colleagues in their original characterization of living organisms as a class of complex selforganized autopoietic systems in 1974.