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The origins of structural operational semantics
 Journal of Logic and Algebraic Programming
, 2004
"... We review the origins of structural operational semantics. The main publication ‘A Structural Approach to Operational Semantics, ’ also known as the ‘Aarhus Notes, ’ appeared in 1981 [G.D. Plotkin, A structural approach to operational semantics, DAIMI FN19, Computer Science Department, Aarhus Unive ..."
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We review the origins of structural operational semantics. The main publication ‘A Structural Approach to Operational Semantics, ’ also known as the ‘Aarhus Notes, ’ appeared in 1981 [G.D. Plotkin, A structural approach to operational semantics, DAIMI FN19, Computer Science Department, Aarhus University, 1981]. The development of the ideas dates back to the early 1970s, involving many people and building on previous work on programming languages and logic. The former included abstract syntax, the SECD machine, and the abstract interpreting machines of the Vienna school; the latter included the λcalculus and formal systems. The initial development of structural operational semantics was for simple functional languages, more or less variations of the λcalculus; after that the ideas were gradually extended to include languages with parallel features, such as Milner’s CCS. This experience set the ground for a more systematic exposition, the subject of an invited course of lectures at Aarhus University; some of these appeared in print as the 1981 Notes. We discuss the content of these lectures and some related considerations such as ‘small state’ versus ‘grand state, ’ structural versus compositional semantics, the influence of the Scott–Strachey approach to denotational semantics, the treatment of recursion and jumps, and static semantics. We next discuss relations with other work and some immediate further development. We conclude with an account of an old, previously unpublished, idea: an alternative, perhaps more readable, graphical presentation of systems of rules for operational semantics.
Algebraic Approaches to Nondeterminism  an Overview
 ACM Computing Surveys
, 1997
"... this paper was published as Walicki, M.A. and Meldal, S., 1995, Nondeterministic Operators in Algebraic Frameworks, Tehnical Report No. CSLTR95664, Stanford University ..."
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Cited by 23 (3 self)
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this paper was published as Walicki, M.A. and Meldal, S., 1995, Nondeterministic Operators in Algebraic Frameworks, Tehnical Report No. CSLTR95664, Stanford University
Solving Recursive Domain Equations with Enriched Categories
, 1994
"... Both preorders and metric spaces have been used at various times as a foundation for the solution of recursive domain equations in the area of denotational semantics. In both cases the central theorem states that a `converging' sequence of `complete' domains/spaces with `continuous' retraction pair ..."
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Cited by 21 (0 self)
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Both preorders and metric spaces have been used at various times as a foundation for the solution of recursive domain equations in the area of denotational semantics. In both cases the central theorem states that a `converging' sequence of `complete' domains/spaces with `continuous' retraction pairs between them has a limit in the category of complete domains/spaces with retraction pairs as morphisms. The preorder version was discovered first by Scott in 1969, and is referred to as Scott's inverse limit theorem. The metric version was mainly developed by de Bakker and Zucker and refined and generalized by America and Rutten. The theorem in both its versions provides the main tool for solving recursive domain equations. The proofs of the two versions of the theorem look astonishingly similar, but until now the preconditions for the preorder and the metric versions have seemed to be fundamentally different. In this thesis we establish a more general theory of domains based on the noti...
Computations, residuals and the power of indeterminacy
 In Timo Lepisto and Arto Salomaa, editors, Proceedings of the Fifteenth ICALP
, 1988
"... We investigate the power of Katmstyle datattow networks, with processes that may exhibit indeterminate behavior. Our main result is a theorem about networks of "monotone " processes, which shows: (1) that the input/output relation of such a network is a total and monotone relation; and (2) every re ..."
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Cited by 20 (10 self)
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We investigate the power of Katmstyle datattow networks, with processes that may exhibit indeterminate behavior. Our main result is a theorem about networks of "monotone " processes, which shows: (1) that the input/output relation of such a network is a total and monotone relation; and (2) every relation that is total, monotone, and continuous in a certain sense, is the input/output relation of such a network. Now, the class of monotone networks includes networks that compute arbitrary continuous inpu*~/output functions, an "angelic merge " network, and an "ilffinityfair merge " network that exhibits countably indeterminate branching. Since the "fair merge " relation is neither monotone nor continuous, a corollary of our main result is the impossibility of implementing fair merge in terms of continuous functions, angelic merge, and infinityfair merge. Our results are established by applying the powerftll technique of "residuals " to the computations of a network. Residuals, which have previously been used to investigate optimal reduction strategies for the Acalculus, have recently been demonstrated by one of the authors (Stark) "also to be of use in reasoning about concurrent systems. Here, we define the general notion of a "residual operation " on an automaton, and show how residual operations defined on the components of a network induce a certain preorder E on the set of computations of the network. For networks of "monotone port automata, " we show that the "fair " computations coincide with Xmaximal computations. Our results follow from this extremely convenient property. 1
Socially Responsive, Environmentally Friendly Logic
 in Truth and Games: Essays in Honour of Gabriel Sandu, Aho, Tuomo and AhtiVeikko Pietarinen, eds., Acta Philosophica Fennica
, 2006
"... We consider the following questions: What kind of logic has a natural semantics in multiplayer (rather than 2player) games? How can we express branching quantifiers, and other partialinformation constructs, with a properly compositional syntax and semantics? We develop a logic in answer to these ..."
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Cited by 7 (0 self)
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We consider the following questions: What kind of logic has a natural semantics in multiplayer (rather than 2player) games? How can we express branching quantifiers, and other partialinformation constructs, with a properly compositional syntax and semantics? We develop a logic in answer to these questions, with a formal semantics based on multiple concurrent strategies, formalized as closure operators on KahnPlotkin concrete domains. Partial information constraints are represented as coclosure operators. We address the syntactic issues by treating syntactic constituents, including quantifiers, as arrows in a category, with arities and coarities. This enables a fully compositional account of a wide
The Weakest Precondition Calculus: Recursion and Duality
 Formal Aspects of Computing
, 1994
"... . An extension of Dijkstra's guarded command language is studied, including unbounded demonic choice and a backtrack operator. We consider three orderings on this language: a refinement ordering defined by Back, a new deadlock ordering, and an approximation ordering of Nelson. The deadlock ordering ..."
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Cited by 7 (3 self)
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. An extension of Dijkstra's guarded command language is studied, including unbounded demonic choice and a backtrack operator. We consider three orderings on this language: a refinement ordering defined by Back, a new deadlock ordering, and an approximation ordering of Nelson. The deadlock ordering is in between the two other orderings. All operators are monotonic in Nelson's ordering, but backtracking is not monotonic in Back's ordering and sequential composition is not monotonic for the deadlock ordering. At first sight recursion can only be added using Nelson's ordering. We show that, under certain circumstances, least fixed points for nonmonotonic functions can be obtained by iteration from the least element. This permits the addition of recursion even using Back's ordering or the deadlock ordering in a fully compositional way. In order to give a semantic characterization of the three orderings that relates initial states to possible outcomes of the computation, the relation betwe...
A Compositional Game Semantics for MultiAgent Logics of Partial Information
"... We consider the following questions: What kind of logic has a natural semantics in multiplayer (rather than 2player) games? How can we express branching quantifiers, and other partialinformation constructs, with a properly compositional syntax and semantics? We develop a logic in answer to these ..."
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Cited by 3 (0 self)
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We consider the following questions: What kind of logic has a natural semantics in multiplayer (rather than 2player) games? How can we express branching quantifiers, and other partialinformation constructs, with a properly compositional syntax and semantics? We develop a logic in answer to these questions, with a formal semantics based on multiple concurrent strategies, formalized as closure operators on KahnPlotkin concrete domains. Partial information constraints are represented as coclosure operators. We address the syntactic issues by treating syntactic constituents, including quantifiers, as arrows in a category, with arities and coarities. This enables a fully compositional account of a wide
On the Semantics of Refinement Calculi
, 2000
"... Refinement calculi for imperative programs provide an integrated framework for programs and specifications and allow one to develop programs from specifications in a systematic fashion. The semantics of these calculi has traditionally been de ned in terms of predicate transformers and poses several ..."
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Cited by 2 (1 self)
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Refinement calculi for imperative programs provide an integrated framework for programs and specifications and allow one to develop programs from specifications in a systematic fashion. The semantics of these calculi has traditionally been de ned in terms of predicate transformers and poses several challenges in defining a state transformer semantics in the denotational style. We de ne a novel semantics in terms of sets of state transformers and prove it to be isomorphic to positively multiplicative predicate transformers. This semantics disagrees with the traditional semantics in some places and the consequences of the disagreement are analyzed.
Semantics, Orderings and Recursion in the Weakest Precondition Calculus
 Proceedings Rex Workshop on Semantics: Foundations and Applications, LNCS 666
, 1993
"... An extension of Dijkstra's guarded command language is studied, including sequential composition, demonic choice and a backtrack operator. We consider three orderings on this language: a refinement ordering defined by Back, a new deadlock ordering, and an approximation ordering of Nelson. The deadlo ..."
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An extension of Dijkstra's guarded command language is studied, including sequential composition, demonic choice and a backtrack operator. We consider three orderings on this language: a refinement ordering defined by Back, a new deadlock ordering, and an approximation ordering of Nelson. The deadlock ordering is in between the two other orderings. All operators are monotonic in Nelson's ordering, but backtracking is not monotonic in Back's ordering and sequential composition is not monotonic for the deadlock ordering. At first sight recursion can only be added using Nelson's ordering. By extending the theory of fixed points in partial orderings we show that, under certain circumstances, least fixed points for non monotonic functions can be obtained by iteration from the least element. This permits us the addition of recursion even using Back's ordering or the deadlock ordering. In order to give a semantic characterization of the three orderings that relates initial states to possible outcomes of the computation, the relations between predicate transformers and discrete powerdomains is studied. Three powerdomains are considered: two versions of the Smyth powerdomain and the EgliMilner powerdomain. For each of them an isomorphism is proved with a suitable domain of predicate transformers. 1991 Mathematics Subject Classification: 68Q55, 68Q10, 68Q60, 06A06. 1991 CR Categories: D.3.1, F.1.2, F.3.1, F.3.2. Keywords and Phrases: weakest preconditions, predicate transformers, refinement, deadlock, backtracking, fixed points, fixed point transformations, Smyth powerdomain, EgliMilner powerdomain, recursion, denotational semantics. Note: The research of Marcello Bonsangue was initially supported by a grant of the Universita' degli Studi di Milano, Italy, and later by a grant o...