David Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253-271, 1995.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....encoded a language of the POOLfamily [Ame89] into ACP. Nevertheless, object oriented concepts like object identity and scoping are more naturally modelled in name passing process calculi. The calculus has been used as the setting for similar studies. A brief account of these follows. 1. Walker [Wal95] was the rst to use the calculus to give semantics to a parallel object oriented language, proving a correspondence between this semantics and a transitional semantics of the language; 2. Liu and Walker [LW98] and Philipou and Walker [PW98] study the correctness of transformation rules that ....

David Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253-271, 1995.

....logic variables or more generally constraints as inspired by [Mah87, SRP91] Our motivation in concurrent calculi lies in the design of programming languages. Concurrency enables us to integrate multiple programming paradigms such as functional [Mil92, Smo94, Nie94, Iba95, PT95b] object oriented [Vas94, PT95a, HSW95, Wal95], and constraint programming [JH91, SSW94] All these paradigms are supported by the programming language Oz [Smo95a, Smo95b] In this paper, we model the time complexity of eager and lazy functional computation in a concurrent calculus. The importance of complexity is three fold: 1. Every ....

David Walker. Objects in the -calculus. Journal on Information and Computation, 116:254-- 273, 1995.

....logic variables or more generally constraints as inspired by [Mah87, SRP91] Our motivation in concurrent calculi lies in the design of programming languages. Concurrency enables us to integrate multiple programming paradigms such as functional [Mil92, Smo94, Nie94, Iba95, PT95b] object oriented [Vas94, PT95a, HSW95, Wal95], and constraint programming [JH91, SSW94] All these paradigms are supported by the programming language Oz [Smo95a, Smo95b] In this paper, we model the time complexity of eager and lazy functional computation in a concurrent calculus. The importance of complexity is three fold: 1. Every ....

David Walker. Objects in the -calculus. Journal on Information and Computation, 116:254--273, 1995.

....by a formal speci cation of an abstract machine for TyCO[15] This abstract machine grows from Turner s abstract machine for Pict [22] but modi es it in the following major ways: 1. objects are rst class entities and substitute input processes. Objects are more ecient than Pict s encoding in [26] both in reduction and heap usage; 2. we use recursion instead of replication for persistence. This allows a cleaner design of the abstract machine no need for distinct and rules, and allows a more rational heap usage; 3. we introduce a new syntactic category the thread that ....

.... The execution of methods in concurrent objects by a client process is achieved by rst interacting with a server process (that serves requests to the object and acts like a lock ensuring mutual exclu A Virtual Machine for a Process Calculus 15 sion) followed by the method invocation proper [26]. This protocol for method invocation involves two synchronizations as opposed to one in TyCO that uses branching structures. Moreover, this encoding of objects produces large amounts of computational garbage in the form of unused channels and process closures. Also, Pict uses replication to model ....

D. Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253-271, 1995.

....in CCP of Tell agents attempting to add inconsistent information to the store. 7 Future Work We propose three main directions for future work on this topic: ffl Among the most successful work in parallel object oriented programming languages is that on the POOL family of languages [Ame89] [Wal95] provides a semantics for a member of this family, via a phrase by phrase translation into the calculus. In particular, an object is represented as an agent whose algebraic structure reflects the internal structure of the object, and whose pattern of interaction captures the way in which the ....

D. Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253--271, 1995.

....a formal specification of an abstract machine for TyCO[15] This abstract machine grows from Turner s abstract machine for Pict [22] but modifies it in the following major ways: 1. objects are first class entities and substitute input processes. Objects are more e#cient than Pict s encoding in # [26] both in reduction and heap usage; 2. we use recursion instead of replication for persistence. This allows a cleaner design of the abstract machine no need for distinct and rules, and allows a more rational heap usage; 3. we introduce a new syntactic category the thread that ....

.... The execution of methods in concurrent objects by a client process is achieved by first interacting with a server process (that serves requests to the object and acts like a lock ensuring mutual exclu A Virtual Machine for a Process Calculus 15 sion) followed by the method invocation proper [26]. This protocol for method invocation involves two synchronizations as opposed to one in TyCO that uses branching structures. Moreover, this encoding of objects produces large amounts of computational garbage in the form of unused channels and process closures. Also, Pict uses replication to model ....

D. Walker. Objects in the #-calculus. Journal of Information and Computation, 116(2):253--271, 1995.

.... = x ok[0] Action[s,b] and Get(z,s,b) z five(x) new v b get[5,v] v done = x ok[5] Action[s,b] prob = x sorry Action[s,b] ten(x) new v b get[10,v] v done = x ok[10] Action[s,b] prob = x sorry Action[s,b] twenty(x) new v b get[20,v] v done = x ok[20] Action[s,b] prob = x sorry Action[s,b] amount(u,x) new v b dep[u,v] v done = x ok[u] Action[s,b] prob = x sorry Action[s,b] reset(x) x ok[0] Action[s,b] and State(z,s,b) z val(x) new v b val[v] v done(u) x ok[u] Action[s,b] prob = x sorry ....

.... = x ok Action[s,b,x] and Get(s,b,x) s five = new v b get[5,v] v done = x ok[5] Action[s,b,x] prob = x sorry Action[s,b,x] ten = new v b get[10,v] v done = x ok[10] Action[s,b,x] prob = x sorry Action[s,b,x] twenty = new v b get[20,v] v done = x ok[20] Action[s,b,x] prob = x sorry Action[s,b,x] amount(u) new v b dep[u,v] v done = x ok[u] Action[s,b,x] prob = x sorry Action[s,b,x] reset = x ok Action[s,b,x] and State(s,b,x) new v b val[v] v done(u) x ok[u] Action[s,b,x] prob = x sorry ....

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D. Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253{ 271, 1995. 14

.... calculus is: calculus: uhxi : P j u(y) Q which can evolve into P j Qfx=yg through communication over the name u. The expressive power of mobile processes has been established by using the calculus for semantics of programming languages such as PICT [9] and of objectoriented programming [16], for encoding higher order communications [10] and the calculus [3] Sequential logic programming [2] and simple concurrent constraint programming [15] have also been modelled: in both these cases, the major obstacle has been expressing logical variables, which can be updated from several ....

D. Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253--271, 1995.

....transmitted are again ports. There is no difference in kind between ports and data, and they are collectively called names. The calculus has a considerable expressive power, as witnessed by its use in, e.g. the semantics of the programming language PICT [PRT93] and of object oriented programming [Wal95] it can naturally encode higher order communications [San92] and the calculus [Mil92] There is a variety of proof methods based on bisimulations [MPW92, San96, San92, San95, PS96] rewrite systems [PS95] and model checking [Dam93, AD96] and automated tools for these are emerging [VM94, ....

D. Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253--271, 1995. 21

.... reset(x) x ok[0] Action[s,b] and Get(z,s,b) z five(x) new v b get[5,v] v done = x ok[5] Action[s,b] prob = x sorry Action[s,b] ten(x) new v b get[10,v] v done = x ok[10] Action[s,b] prob = x sorry Action[s,b] twenty(x) new v b get[20,v] v done = x ok[20] Action[s,b] prob = x sorry Action[s,b] amount(u,x) new v b dep[u,v] v done = x ok[u] Action[s,b] prob = x sorry Action[s,b] reset(x) x ok[0] Action[s,b] and State(z,s,b) z val(x) new v b val[v] v done(u) x ok[u] Action[s,b] prob = x sorry ....

.... , reset(x) x ok Action[s,b] and Get(s,b,x) s five = new v b get[5,v] v done = x ok[5] Action[s,b,x] prob = x sorry Action[s,b,x] ten = new v b get[10,v] v done = x ok[10] Action[s,b,x] prob = x sorry Action[s,b,x] twenty = new v b get[20,v] v done = x ok[20] Action[s,b,x] prob = x sorry Action[s,b,x] amount(u) new v b dep[u,v] v done = x ok[u] Action[s,b,x] prob = x sorry Action[s,b,x] reset(x) x ok Action[s,b,x] and State(s,b,x) new v b val[v] v done(u) x ok[u] Action[s,b,x] prob = x sorry Action[s,b,x] ....

[Article contains additional citation context not shown here]

D. Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253{ 271, 1995.

....only persistent objects where methods are input processes assigned to distinct channels. Mutual exclusive execution of methods in an object is achieved by sending the object a message that carries its state. Only then can a method be invoked. This makes method invocation a two way protocol [26] in Pict, as opposed to one way in T yCO. Oz procedures have encapsulated state so that objects can be defined directly as sets of methods (procedures) acting over their state (represented as a set of logical variables) This representation is quite close to objects in our own abstract machine if ....

David Walker. Objects in the ß-calculus. Journal of Information and Computation, 116(2):253--271, 1995.

.... experimentation with the semantics, the translation was implemented in the form of a compiler from Erken to the concurrent functional programming language Facile [TLP 93] The calculus has previously been used in giving semantics to object oriented programming and design languages [Jon93, Wal95] The existence of these previous works was indeed a compelling argument for defining the semantics of Erken in such a way. Our work differs from [Jon93, Wal95] in mainly two aspects: i) the defined language permits intra object concurrency, i.e. several execution threads are allowed to ....

....[TLP 93] The calculus has previously been used in giving semantics to object oriented programming and design languages [Jon93, Wal95] The existence of these previous works was indeed a compelling argument for defining the semantics of Erken in such a way. Our work differs from [Jon93, Wal95] in mainly two aspects: i) the defined language permits intra object concurrency, i.e. several execution threads are allowed to co exist in the same object, and (ii) our focus and motivation is on prototyping language constructs, via an implementation of the translation function, rather ....

D. Walker. Objects in the ß-calculus. Journal of Information and Computation, 116(2):253--271, 1995.

....Although there is yet no definite measure on its expressiveness there is strong evidence that its primitives are enough for a wide variety of purposes. Within the calculus it is possible to naturally encode the functional paradigms of the calculus [Mil92] and of object oriented formalisms [Wal95]. The ability to directly represent mobility, in the sense of processes that reconfigure their interconnection structure when they execute, makes it easy to model systems where processes move between different locations and where resources are allocated dynamically [OP92, Ora94] It can also ....

D. Walker. Objects in the ß-calculus. Journal of Information and Computation, 116(2):253--271, 1995.

....Bjorn.Victor DoCS.UU.SE y Dept. of Teleinformatics, Royal Institute of Technology, Sweden, joachim it.kth.se The expressive power of mobile processes has been established by using the calculus for semantics of programming languages such as PICT [PT97] and of object oriented programming [Wal95], for encoding higher order communications [San93] and the calculus [Mil92] Sequential logic programming [Li94] and simple concurrent constraint programming [VP96] have also been modelled: in both these cases, the major obstacle has been expressing logical variables, which can be updated from ....

D. Walker. Objects in the ß-calculus. Journal of Information and Computation, 116(2):253-- 271, 1995.

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David Walker. Objects in the -calculus. Journal of Information and Computation, 116(2):253-271, 1995.

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