S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP97, LNCS 1330. Springer, 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....identified by a query mark before the name that defines the policy behavior. policy Private( user set OrgUsers ) object set IDocs; Policy data Private: Rule name. event.action = SendEmail Applicability event.target IN IDocs expression. Separation marker. event.par[1] IN OrgUsers Aceptability expression. Figure 8: Simple policy stating that objects belonging to IDocs can only be sent to users belonging to OrgUsers. Figure 8 shows a simple policy stating that documents internal to the entity defining the policy cannot be sent to someone outside the ....

....inside the policy. These constraints can then be further simplified by the rule of the consistency engine. private(Event, OrgUsers, Locals, Globals, R) # Event = event(Actor,Action,Target,Pars, Time) Locals = locals(private vars(IDocs) R = r( Action = SendMail # Target # IDocs, Pars[1] # OrgUsers) Figure 12: The figure shows the translation of the SPL policy of Figure 8 to CHR. Figure 12 shows the translation of the SPL policy presented in figure 8. The policy is translated into a simplification rule with two constraints in the body. One of the constraints states that the ....

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. Lecture Notes in Computer Science, 1330:252--267, 1997.

....declarative language extension of the CLP scheme, especially developed to implement special purpose constraint solvers for user defined constraints. CHRs are rewriting rules that are used to simplify and solve constraints. The operational semantics of CHRs is defined by a transition system [1, 7]: The states are annotated pairs hC U ; CB i v . C U is a conjunction of user defined constraints called user defined store, CB a conjunction of built in constraints called built in store, and v the set variables one is interested in. Other variables 1 may be constrained, too, but they are out ....

....of other variable bindings out of interest. Furthermore, the deletion of some initial constraints, e.g. marked with 2, requires the deletion of several local variable bindings, which are not really necessary. To improve this unsatisfying situation, the elimination of local variables is proposed in [1, 2]. In this paper, the elimination of local variables by projection is presented. In the considered context, the adaptation of CHR derivations, elimination is restricted to variables having rational trees as its domains. One kind of elimination, the so called early projection (cf. 3, 4] is ....

Slim Abdennadher. Operational semantics and confluence of constraint handling rules. In Proceedings of the Third International Conference on Principles and Practice of Constraint Programming -- CP97, number 1330 in Lecture Notes in Computer Science. Springer Verlag, 1997.

....for computing primes are contained in the solver primes.chr of the CHR library [FrBr96] 4. SYNTAX AND SEMANTICS In this section we give an overview of syntax and semantics as well as soundness and completeness results for constraint handling rules. More detailed presentations can be found in [FAM97, Abd97, Abd98]. We assume some familiarity with (concurrent) constraint (logic) programming [JaLa87, vH91, Fr 92, Sar93, JaMa94] As a special purpose language, CHR extend a host language with (more) constraint solving capabilities. Auxiliary computations in CHR programs are directly executed as host language ....

....are applied fairly, i.e. that every rule that is applicable is applied eventually. Fairness is respected and trivial non termination is avoided by applying a propagation rule at most once to the same constraints. A more complex operational semantics that addresses these issues can be found in [Abd97, Abd98]. Initial and Final States Definition 4.5. The initial state consists of a goal F and empty constraint stores, hF; true; trueiV , where V is the sequence of variables occurring in F . A final state is either of the form hF; E; falseiV (such a state is called failed) or of the form htrue; E; ....

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S. Abdennadher, Operational Semantics and Confluence of Constraint Propagation Rules, 3rd Intl Conf on Principles and Practice of Constraint Programming (CP'97), Linz, Austria, Springer LNCS 1330, pp 252-265, October/November 1997.

....in Constraint Handling Rules (CHRs) 10] the adaptation of DCSP solutions requires the adaptation of the built in constraints and their solution sets. These built in constraints have in common that syntactical equations either over finite or rational trees are taken as a basis (cf. [1]) Thus, the adaptation of syntactical equations and their solution sets is a fundamental task in a CHR implementation applicable to solve DCSPs. Example 1. Let the linear equations X Z Pi = 2 and X Gamma Z Pi = 0 be given. Further, it is assumed that there is a CHR program including the ....

Slim Abdennadher. Operational semantics and confluence of constraint handling rules. In Proceedings of the Third International Conference on Principles and Practice of Constraint Programming -- CP97, number 1330 in Lecture Notes in Computer Science. Springer Verlag, 1997.

....is mainly based on head matching and guard entailment, which are at least entailment problems over syntactical equations The research in this paper was supported by the German Federal Ministry for Education, Science, Research, and Technology (BMBF) under grant no. 01 IN 507 B. cf. [1]) Thus, the solution adaptation of entailment problems is a fundamental task for an adaptation of CHR derivations in dynamic environments. Example 1. Let the linear equations X Z Pi = 2 and X Gamma Z Pi = 0 be given. Further, it is assumed that there is a CHR program including the ....

Slim Abdennadher. Operational semantics and confluence of constraint handling rules. In Proceedings of the Third International Conference on Principles and Practice of Constraint Programming -- CP97, number 1330 in Lecture Notes in Computer Science. Springer Verlag, 1997.

No context found.

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP'97, LNCS 1330. Springer-Verlag, 1997.

No context found.

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP97, LNCS 1330. Springer-Verlag, 1997.

....logically redundant information which may make it possible for other rules to be activated. Notice that simplification and propagation applies matching and not unification: H 0 must be an instance of H , i.e. the derivation step can only instantiate 1 This to prevent trivial nontermination; see [2] for the formalization of a computation rule with the indicated properties. variables of H but not variables of H 0 . If unification were used instead of matching in a committed choice language such as CHR , completeness would be lost. The Split transition can always be applied to a ....

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP97, LNCS 1330. Springer-Verlag, November 1997.

....rules, CHR provides two features which are essential for non trivial constraint handling. Due to space limitations, we cannot give a formal account of syntax and semantics of CHR in this paper. An overview on CHR can be found in [Fru95] Detailed semantics results for CHR are available in [Abd97] 4.1 Domains Constraint solving for finite domains constraints is based on consistency techniques [Mac92, Kum92] For example, the constraints X : 2, 3, 4] i.e. X must take a value from the list [2, 3, 4] and X : 3, 4, 5] may be replaced by the new constraint X : 3, 4] Implementing ....

Slim Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Princi12 ples and Practice of Constraint Programming, LNCS 1330. Springer, 1997.

....rules, CHR provides two features which are essential for non trivial constraint handling. Due to space limitations, we cannot give a formal account of syntax and semantics of CHR in this paper. An overview on CHR can be found in [10] Detailed semantics results for CHR are available in [1]. We introduce CHR by example. Let = and = be built in constraint symbols. We implement a user defined constraint for max, where max(X,Y,Z) means that Z is the maximum of X and Y: max(X,Y,Z) X= Y Z=Y. max(X,Y,Z) Y= X Z=X. max(X,Y,Z) X= Z, Y= Z. The first rule states that ....

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP'97, LNCS 1330. Springer-Verlag, 1997.

....abstraction of execution traces. In case of equivalence based on operational semantics expressed by a transition system, it is common to define as observables the results of finite computations, where one abstracts away local variables, see e.g. EGM98] We have already shown in previous work [Abd97] that analysis techniques are available for an important property of any constraint solver, namely confluence: The result of a computation should be independent from the order in which constraints arrive and in which rules are applied to the constraints. For confluence of terminating CHR programs ....

....any constraint solver, namely confluence: The result of a computation should be independent from the order in which constraints arrive and in which rules are applied to the constraints. For confluence of terminating CHR programs we were able to give a decidable, sufficient and necessary condition [Abd97,AFM99]. A completion algorithm that makes programs confluent if it terminates, was presented in [AF98] It is tempting to think that a suitable modification of the concept of confluence can be used to express equivalence of programs. In this paper we show that a straightforward application of our ....

[Article contains additional citation context not shown here]

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP97, LNCS 1330. Springer-Verlag, November 1997.

....that it keeps the constraints H 0 in the state. Trivial nontermination caused by applying the same propagation rule again and again is avoided by applying a propagation rule at most once to the same constraints. A more complex operational semantics that addresses this issue can be found in [Abd97]. 2.2 CHR by Example Finite domains appeared first in CHIP [vH89] by incorporating consistency algorithms [Mac77, Mac92] into constraint logic programming. Implementing these techniques with CHR is straightforward. The constraint X: Dom means that the value for the variable X must be in the ....

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, LNCS 1330. Springer, 1997.

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Abd97. S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP'97, LNCS. Springer, November 1997.

....language for writing constraint solvers either from scratch or by modifying existing solvers. An important property of any constraint solver is confluence: The result of a computation should be independent from the order in which constraints arrive and in which rules are applied. In previous work [Abd97] a sufficient and necessary condition for the confluence of terminating CHR programs was given by adapting and extending results about conditional term rewriting systems. In this paper we investigate so called completion methods that make a non confluent CHR program confluent by adding new ....

.... constructs (backward and forward chaining, suspension, compiler optimization, debugging) can be implemented once and for all; for the user only one set of ideas need to be understood, though with rich (albeit disciplined) variations (constraint systems) We have already shown in previous work [Abd97] that analysis techniques are available for an important property of any constraint solver, namely confluence: The result of a computation should be independent from the order in which constraints arrive and in which rules are applied. For confluence of terminating CHR programs we were able to ....

[Article contains additional citation context not shown here]

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP'97, LNCS 1330. Springer-Verlag, November 1997.

....CU ; CB 7 G B; H 0 CU ; C H =H 0 CB Fig. 3. CHR computation steps caused by applying the same propagation rule again and again is avoided by applying a propagation rule at most once to the same constraints. A more complex operational semantics that addresses this issue can be found in [1]. In contrast to SLD resolution, CHR is a committed choice language. That is, whenever more than one transition is possible, one transition is chosen nondeterministically (in the sense of don t care nondeterminism, i.e. without backtracking) 3 CHR as a Logic Programming Language It is ....

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP'97, LNCS 1330. Springer, 1997.

....rules, CHR provides two features which are essential for non trivial constraint handling. Due to space limitations, we cannot give a formal account of syntax and semantics of CHR in this paper. An overview on CHR can be found in [Fru95] Detailed semantics results for CHR are available in [Abd97]. 4.1 The solver It is common to use the notation X: Dom to state that the value for the variable X must be member of the given finite domain Dom. More precisely, if Dom is a list, then X must be a number appearing in Dom, and if Dom is an interval A. B, then X must be a number between A and ....

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP'97, LNCS 1330. Springer-Verlag, 1997.

No context found.

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP97, LNCS 1330. Springer, 1997.

No context found.

Abdennadher, S., Operational Semantics and Confluence of Constraint Propagation Rules, in: G. Smolka, editor, Proceedings of the Third International Conference on Principles and Practice of Constraint Programming, 1997, pp. 252--266.

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Slim Abdennadher. Operational Semantics and Confluence of Constraint Propagation Rules. In Gert Smolka, editor, CP'97: Proceedings of the 3rd International Conference on Principles and Practice of Constraint Programming, pages 252--266, Schloss Hagenberg, Austria, 1997. Springer Verlag.

No context found.

Slim Abdennadher. Operational semantics and confluence of constraint propagation rules. In Third International Conference on Principles and Practice of Constraint Programming, CP97, LNCS 1330. Springer, 1997.

No context found.

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Gert Smolka, editor, Proceedings of the Third International Conference on Principles and Practice of Constraint Programming, pages 252--266, 1997.

No context found.

S. Abdennadher. Operational semantics and confluence of constraint propagation rules. In Gert Smolka, editor, Proceedings of the Third International Conference on Principles and Practice of Constraint Programming, pages 252--266, 1997.

No context found.

S. ABDENNADHER, Operational semantics and confluence of constraint propagation rules, Lecture Notes in Computer Science, 1330 (1997), pp. 252--267.

No context found.

S. Abdennadher, Operational semantics and confluence of constraint propagation rules, Proc. Int. Conf. on Principles and Practice of Constraint Programming, LNCS 1330, 252--265, 1997.

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