Milner R., Elements of Interaction, CACM, vol.36, no.1, Jan. 1993, 78-89.  Home/Search   Document Not in Database   Summary   ACM   TOC   Related Articles   Check

....with the environment in which the system is placed and to maintain a well de ned action reaction behavior. In the late nineteen seventies and early nineteen eighties, this behavior of systems received much attention in the formal speci cation and veri cation of concurrent processes (see Milner [11, 12]) The term reactive systems was introduced to refer to systems with this kind of behavior. Pnueli [14] p. 511) writes: Reactivity characterizes the nature of interaction between the system and its environment. It states that this interaction is not restricted to accepting inputs on ....

R. Milner. Elements of interaction, C.ACM 36:1 (1993) 78-89.

....of system behavior. This work is part of a larger e ort towards a more comprehensive formalization of interactive computation, with the aim of characterizing empirical computation by interaction. 1 Introduction In this paper, we adopt Milner s interactive view of system behavior [Mi1]. This view is more general than the algorithmic view [Kn, Pa] extending the one input one output computational model of Turing Machines (TMs) to computations that involve sequences of interactions. It is interesting to note that the distinction between automatic machines and choice machines, ....

Robin Milner. Elements of Interaction. Communications of the ACM, January 1993.

....definition, we are able to build complex services by writing service algebra expressions. This model explicitly takes into account user interaction and is based on a well formed semantic as will be shown later. Explicit treatment of user interaction provides a more powerful computational model [19, 34]. In addition, by means of a set of algebra properties, we are able to simplify and optimize service expressions into a minimal form guaranteeing the same semantic of initial expressions. # ## 9rsvv#v Let h 1 #####h n be n constant terms, we call #fyr the vector t = h 1 #####h n ) where ....

....with the external environment. Despite their usefulness, however they do not represent p f#h#v hy models that can formalize computational processes (e.g. relational calculus, lambda calculus etc. In other words, these models are devised to specify, rather than to compute. Wegner [34] and Milner [19] focused more on the investigation of the interaction from a computational point of view by founding the area of v#r. hp#vo oor#p f#vt. Wegner argues that interactions cannot be described by algorithms, due to the intrinsically non algorithmic evolution of interaction between user and machine. A ....

R. Milner. Elements of interaction.###################### ##(1):78-89 (1993).

.... transformer) semantics defined in [Plo79] The standard example to show that compositionality is lost when introducing parallel composition is that the programs x : 2 and x : 1 ; x : x 1 are semantically equivalent, but x : 2 k x : 3 and (x : 1 ; x : x 1) k x : 3 are not (see, e.g. [Mil93]) The state transformation semantics and the predicate transformer semantics to be presented are mappings from statements to state transformations and predicate transformers, respectively. Before we come to these semantics, we first discus the state transformations and the predicate transformers ....

R. Milner. Elements of Interaction. Communications of the ACM, 36(1):78--89, January 1993.

....onset. The second source of unpredictability in agent oriented systems relates to the notion of emergent behaviour. It has long been recognised that interactive composition collections of processes (agents) acting side by side and interacting in whatever way they have been designed to interact [43] results in behavioural phenomena that cannot be deconstructed solely in terms of the behaviour of the individual components. That is, the whole is often greater than the sum of the parts. Such emergent behaviour is a consequence of the interaction between components and given their ....

R. Milner, Elements of interaction, Comm. ACM 36 (1) (1993) 78--89.

....Turing machine must accommodate interaction and in nite computations. Neither of the two features by itself is new in computer science. Notions of interaction and of interactive computing have already received considerable attention, for example, in the theory of concurrent processes (cf. Milner [21,22] and Pnueli [28,29] and in the design of programming systems for parallel processes (cf. 10] Interaction is also fundamental in the many studies of communication protocols and distributed algorithms in which the building blocks act as (restricted) interactive Turing machines (cf. 4] 20] ....

R. Milner. Elements of interaction, C.ACM 36:1 (1993) 78-89.

.... This paper can be viewed as an application of these approaches to Persistent Turing Machines (PTMs) bringing together several separate threads to further formalize interactive models of computation: coalgebraic theory [BM, Ru, Jac1] transducer theory [Ne, Mo, Har, Hol] interaction [Mi, WG2, WG1, Gol] Overview Section 2 provides a background discussion about state machines, interactive devices, and Persistent Turing Machines. Section 3 defines formally the PTM model, and discusses the notions of equivalence and expressiveness for PTMs. In Section 4.2, we define the minimization of PTMs, by ....

Robin Milner. Elements of Interaction. Communications of the ACM 36:1 (1993), pp. 78-89.

....structural and interaction properties as a CORBA object if we restrict to an untyped world. For this reason we exploit a new formalism for our modelling purposes, an algebra of actors [11, 10, 9] which has been designed as a compromise between the standard process algebras, such as the calculus [24], and the actor model. This process algebra supports an high level specification style which allows the user to describe how CORBA models of request invocation can be mapped into sequences of message passing primitives. 2.4 The Actor Model The actor model was introduced by Carl Hewitt about 20 ....

.... past few years, several advances have been achieved on the semantics of actors, dealing with aspects of communication and concurrency [4, 3, 30, 31, 21] but these papers do not investigate the relationships of the actor model with traditional process algebras, even though recently Robin Milner [24] suggested that it may be worthwhile to work in this direction. We believe that our approach is complementary to previous approaches to the semantics of actors, providing a new framework to discuss concurrency related aspects in this context. The reader interested in a more detailed comparison ....

R. Milner. Elements of interaction. Communications of the ACM, 36(1):79--89, January 1993.

.... and results from many diverse research areas, ranging from philosophical studies on human communication [11, 36] and the design of agent languages in AI [12, 27, 25, 35] to the development of parallel and distributed programming languages [1, 7, 8, 9, 43] and the theory of concurrency [23, 28, 30]. In fact, on the one hand, a collection of agents will often include humans performing some of the tasks; thus, it is essential that a communication language for software agents include features that facilitate the interaction of people with them. On the other hand, such a communication language ....

....we would like to capture a minimal set of primitives for agent communication languages. Indeed, as Robin Milner stated in his Turing award lecture a theory of concurrency and interaction requires a new conceptual framework, not just a refinement of what we find natural for sequential computing [30]. For this purpose, we analyze multi agent systems and their communication protocols based on speech acts theory, in order to single out a set of basic interaction primitives. The multi agent systems we are considering are systems composed of a fixed set of intelligent software agents, ....

R. Milner. Elements of interaction. Communications of the ACM, 36(1):79--89, January 1993. 33

....especially when the number of concurrent activities is large, because we do not have proper models to cope with the resulting complexity. This, at least to some extent, is a chicken and egg problem. Theoretical work on concurrency, e.g. CSP[1, 2] CCS[3] process algebra[4] and calculus[5, 6], has helped to unveil the essence of the problems. However, the models of concurrency proposed and studied in such theoretical work, understandably, are not always directly useful for practical programming. A number of programming languages have used some of these theoretical models as their ....

R. Milner, "Elements of interaction," Communications of the ACM, vol. 36, pp. 78--89, January 1993. 29

....structural and interaction properties as a CORBA object if we restrict to an untyped world. For this reason we exploit a new formalism for our modelling purposes, an algebra of actors [10, 8, 7] which has been designed as a compromise between the standard process algebras, such as the calculus [21], and the actor model. This process algebra supports an high level specification style which allows the user to describe how CORBA models of request invocation can be mapped into sequences of message passing primitives. 2.4 The Actor Model The actor model was introduced by Carl Hewitt about 20 ....

.... past few years, several advances have been achieved on the semantics of actors, dealing with aspects of communication and concurrency [4, 3, 27, 28, 18] but these papers do not investigate the relationships of the actor model with traditional process algebras, even though recently Robin Milner [21] suggested that it may be worthwhile to work in this direction. We believe that our approach is complementary to previous approaches to the semantics of actors, providing a new framework to discuss concurrency related aspects in this context. The reader interested to a more detailed comparison ....

R. Milner. Elements of interaction. Communications of the ACM, 36(1):79--89, January 1993.

....Most of these process algebras, however, are based on static models. For example, in CSP channel names are constants and are not first class objects, which means that they cannot be passed as values between communicating processes. A few solutions do exist such as that proposed by the calculus [9]. In the calculus, a channel is regarded just as a value and therefore can be sent between processes. A second important property of the calculus is to allow new (fresh) names to be defined. These two properties support the dynamic variations of a configuration, where processes can create new ....

....the processes. In this case, a process must know the identities of the processes it can communicate with or it can be informed by other processes about the identity of the those unknown processes. To illustrate this situation, assume the example similar to the mobile telephone network presented in [9]. Figure 1 shows a Car (telephone) process with channels, one to talk and another one to switch from the current station to another station. The Station process switches the Car connection when requested by the Central process. Observe that both the Station and Central are involved in the ....

R. Milner. Elements of interaction. Communications of ACM, 36(1):78--97, January 1993.

....the onset. The final source of unpredictability in agent oriented system design relates to the notion of emergent behaviour. It has long been recognised that interactive composition collections of processes acting side by side and interacting in whatever way they have been designed to interact [24] results in behavioural phenomena that cannot be generally understood solely in terms of the behaviour of the individual components. This emergent behaviour is a consequence of the interaction between components. Given the sophistication and flexibility of agent interactions, it is clear that ....

R. Milner (1993) "Elements of interaction" Comms. of ACM 36 (1) 78-89.

....and of non predictability come inherent in computations. The more powerful interaction can be, the less dominating is the algorithm for the behavior the device is actually showing. Not least for that reason, a paradigm shift from algorithmic to interactive view on computing is proposed (see e.g. [Weg98, Mil93]) In theory of computation, modes of interaction were considered as long as the formal notion of an algorithm was made precise. Such modes include well known concepts like oracles, advice functions, or interactive proof systems. All in common is that a computation is only considered until the ....

R. Milner. Elements of interaction. Communications of the ACM, 36:78--89, 1993.

.... past few years, several advances have been achieved on the semantics of actors, dealing with aspects of communication and concurrency [5, 4, 26, 25, 16] but these papers do not investigate the relationships of the actor model with traditional process algebras, even though recently Robin Milner [19] suggested that it may be worthwhile to work in this direction. Thus, the question whether some of the results that have been proved in the context of process algebras can be imported in the actor model and in general in object oriented distributed systems is still an open issue. The main results ....

R. Milner. Elements of interaction. Communications of the ACM, 36(1):79--89, January 1993.

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Milner R., Elements of Interaction, CACM, vol.36, no.1, Jan. 1993, 78-89.

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Milner R., Elements of Interaction, CACM, Jan. 1993, vol.36, no.1, 78-89.

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Milner, R. (1993), Elements of Interaction, CACM, vol.36, no.1, 78-89.

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R. Milner. Elements of interaction. Communications of the ACM, 36(1):79--89, January 1993.

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Milner, R. Elements of interaction. Commun. ACM 36, 1 (Jan. 1993), 78--89.

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Robin Milner. Elements of interaction. CACM, 36(1), 1993.

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Robin Milner. Elements of interaction. CACM, 36(1), 1993.

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Milner R., Elements of Interaction, CACM, vol.36, no.1, Jan. 1993, 78-89.

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Milner R. (1993) Elements of Interaction, CACM, vol.36, no.1, 78-89.

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Robin Milner. Elements of Interaction. CACM , Vol. 36, No. 1, pages 78--89, 1993.

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