He Jifeng. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... between action systems [BKS83] and CSP by expressing the traces, failures and divergences of CSP processes as weakest precondition formulae [Dij76] Butler [But92] addresses the issue of unbounded nondeterminism and extends Morgan s correspondence [Mor90] to the infinite traces model; and He [He89] like Josephs, expresses CSP processes as labelled transition systems and presents sets of sound and complete simulation rules. Woodcock and Morgan [WM90] show also how refinement can be established using simulation rules, this time in the context of the action systems formalism [BKS83] In each ....

.... adopted a state based approach to the refinement and specification of non divergent CSP processes; Morgan [Mor90] defined a correspondence between action systems [BKS83] and CSP by expressing the traces, failures and divergences of CSP processes as weakest precondition formulae [Dij76] and He [He89] like Josephs, expressed CSP processes as labelled transition systems and presented sets of sound and complete simulation rules. In this section we discuss these three approaches and in particular we compare the information content of the simulation rules. Action systems The actions systems ....

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J. He. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement, pages 511 -- 533. Butterworths, 1989.

....class. It is hence most important that this layer 2 (data) refinement concept neatly fits to the layer 3 (process) refinement concept. The relationship between data refinement and failures refinement has been intensively studied, and the duality of data and process refinement has been shown in [Jif89, dRE98]: given a failure divergence semantics for a stateoriented formalism, data refinement induces process refinement. In [FH97] these results have been extended to CSP OZ with its specific combination of blocking and non blocking views of method invocation. I CSP OZ is an object oriented formal ....

He Jifeng. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.

.... encapsulated into two rules: downward and upward simulations [22] These refinement rules are known to be sound and jointly complete, that is anyupwardordownward simulation is a valid refinement, and any refinement can be proved correct by application of appropriate upward and downward simulations [9, 23]. Downward and upward simulations are sometimes also known as forward and backward simulations respectively. The downward simulation rules are more straightforward, and form the usual presentation of refinement (e.g. as in [17] however, upward simulations are occasionally necessary, for ....

J. He. Process refinement. In J. McDermid, editor, The Theory and Practiceof Refinement. Butterworths, 1989.

....briefly at I O automata. 1.4.1 Transition Systems and CSP A labelled transition system is a transition system in which each transition has an associated label. A labelled transition system may be regarded as a CSP process by treating the transition labels as events. Josephs [Jos88] and He Jifeng [He89] have given a CSP semantics to labelled transition systems. Here we look at the work of He Jifeng the work of Josephs is similar though it doesn t deal with divergence. Consider a transition system T = A; S ; I ; TA ) where A is a set of labels, S is a set of states, I S is an ....

....can engage in them. In this way, interaction between T1 and T2 is by synchronisation over shared events as in CSP. 1.4.2 Action Systems and CSP Morgan [Mor90a] has defined failures divergences semantics for (labelled) action systems. However, rather than defining them in terms of relations as in [He89, Jos88], Morgan defines them in terms of weakest precondition formulae. Using weakest preconditions means that there is no need to introduce a special divergent state and so the definitions are less complicated. Morgan Woodcock [WM90] have formulated upwards and downwards simulation in terms of weakest ....

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J. He. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.

....Since the system specification in our approach is a CSP specification, a starting point for the development of refinement and verification methods is the existing CSP methods. A process is a refinement of another in CSP when its failures and divergences are subsets of those of the other process. He[12] and Josephs[17] have developed refinement relations for state transition systems which are both sound and complete with respect to CSP refinement. Woodcock and Morgan[27] have produced similar results using weakest precondition formulae. These approaches could be adopted for refining Object Z ....

J. He. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.

....) for successive messages on a roundrobin basis. In [6] an adaptive routing mechanism is introduced, where congestion information is passed around the network, and the node chosen from table n (i ; r) is on the least congested path to recipient r . 12 Related Work Josephs [16] and He Jifeng [9] have defined the CSP failures of transition systems in which actions are relations between states rather than predicate transformers. He Jifeng defines divergences as well. Both define simulation, hiding and parallel composition in the relational approach. In [9] the divergent state needs to be ....

....Work Josephs [16] and He Jifeng [9] have defined the CSP failures of transition systems in which actions are relations between states rather than predicate transformers. He Jifeng defines divergences as well. Both define simulation, hiding and parallel composition in the relational approach. In [9], the divergent state needs to be modelled explicitly, which complicates the definitions. This is avoided, in our case, by the use of predicate transformers rather than relations. Morgan has already defined the CSP failure divergences semantics of (non value passing) action systems (without ....

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J. He. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.

....techniques for the Object Z component of a specification. This will enable refinements to be verified at the specification level, rather than working explicitly in terms of failures, traces and refusals at the semantic level. Work on state based refinement for concurrent systems goes back to He[10] and Josephs[15] who have developed refinement relations for state based transition systems which are complete and sound with respect to CSP refinement. Woodcock and Morgan[27] have produced similar results in the context of action systems and weakest precondition formulae. In this section we ....

J. He. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.

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He Jifeng. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.

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J. He. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.

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J. He. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989. 29

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He Jifeng. Process refinement. In J. McDermid, editor, The Theory and Practice of Refinement. Butterworths, 1989.

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