K. Sagonas, T. Swift, and D.S. Warren. The limits of fixed-order computation. In International Workshop on Logic and Databases. LNAI: Springer-Verlag, 1995.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....keeps an approximation of the subgoal dependency graph (SDG) of the program in the completion stack (Section 2. 3) During the Completion operation, if negative dependencies are present, the engine has to build the exact SDG of the program explicitly to detect whether negative loops are present [SSW96c, SSW96a] In contrast, an engine based on Local Scheduling can avoid this step. As we have shown in Example 5.2.1, since SCCs are preserved during the evaluation, the completion stack represents the exact SDG of the program, and thus negative dependencies are only created if there are actual ....

K. Sagonas, T. Swift, and D.S. Warren. The limits of fixed-order computation. In International Workshop on Logic and Databases, pages 343--363, 1996.

....it keeps an approximation of the subgoal dependency graph (SDG) of the program in the completion stack (Section 2. 3) During the COMPLETION operation, if negative dependencies are present, the engine has to build the exact SDG of the program explicitly to detect whether negative loops are present [SSW96c, SSW96a] In contrast, an engine based on Local Scheduling can avoid this step. As we have shown in Example 5.2.1, since SCCs are preserved during the evaluation, the completion stack represents the exact SDG of the program, and thus negative dependencies are only created if there are actual ....

K. Sagonas, T. Swift, and D.S. Warren. The limits of fixed-order computation. In International Workshop on Logic and Databases, pages 343--363, 1996. BIBLIOGRAPHY 101

....sections provide a brief introduction to SLG resolution as it is implemented in XSB. For interested users, the ftp directory and web site contain papers covering in detail various aspects of tabling. An overview of SLG resolution, and a practical evaluation strategy for it are provided in [7, 28]. 30, 29, 24, 15, 34, 26] describe fully the SLG WAM as it is implemented in Version 1.7.1, and [35, 6] analyze its performance. 5.1 SLG Evaluation 5.1.1 Tabling Consider the Prolog program ancestor(X,Y) parent(X,Y) ancestor(X,Y) ancestor(X,Z) parent(Z,Y) together with the query ....

....Broadly, a program uses stratified negation whenever there is no recursion through negation. Refining this intuition can lead to an array of stratification classes. While XSB evaluates all programs, whether stratified or not, its evaluation is especially efficient for LRD stratified programs [28], which we now explain. Consider a simple approach to incorporating negation into tabling, and assume, to avoid complications of floundering, that the entire program is ground that no clause of the program contains any variable. Then if all predicates for negative literals are tabled, we ....

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K. Sagonas, T. Swift, and D.S. Warren. The limits of fixed-order computation. In International Workshop on Logic and Databases. LNAI: Springer-Verlag, 1995.

....Representation. Tabling as defined below for WFS has polynomial data completity. 5 Motivation ffl There has been a lot of research into it. Tabling and Related Research Formulation [41] 17] 108] 38] 60] 98] 115] 120] 15] 14] 20] 22] 33] 19] 105] 34] [94], 54] 110] 23] 27] Implementation and Systems [6] 116] 64] 42] 2] 55] 82] 84] 106] 107] 93] 7] 21] 43] 44] 96] 121] 45] 83] 95] 92] Optimizations [30] 6 Motivation Magic Sets and Related Research (e.g. Alexander Method) Formulation [87] ....

....= B and (1) is some i (1 i n) such that L i is false in M i or L i 2 F ; 2) there exists a failing prefix: for all j (1 j i Gamma 1) L j is true in Ig. By adjusting the operations of SLG, a tabling strategy SLG RD can be formulated with the following property. Theorem 3 [94] Given a ground program P , an SLG RD evaluation will only delay on encountering a literal in the ultimate left to right dynamic stratum. We conjecture that a similar theorem is possible for other formalisms such as Well Founded Ordered Search [101] 69 Meta Interpreting in WFS To ....

K. Sagonas, T. Swift, and D.S. Warren. The limits of fixed-order computation. Technical report, SUNY at Stony Brook, 1995.

.... it keeps an approximation of the subgoal dependency graph (SDG) of the program in a stack (the completion stack) During the COMPLETION operation, if negative dependencies are present, the engine has to explicitly build the exact SDG of the program to detect whether negative loops are present [7, 8]. In contrast, an engine based on Local Scheduling can avoid this step: Since SCCs are preserved during the evaluation, the completion stack represents the exact SDG of the program, and thus negative dependencies are only created if there are actual loops through negation. The following example ....

....for local subgoals. The COMPLETION operation for the mixed strategy engine is described in Algorithm 5.5. Note that for negation handling, Integ CheckComplete will act according to the strategy of the leader: for Batched Scheduling it will use the procedures and data structures described in [7] (which are currently implemented in XSB) for Local Scheduling, even though the mechanisms for delay and simplification are the same as for Batched Scheduling, a simpler implementation can be achieved since there is no need to build SDGs, all manipulations required to maintain the necessary ....

K. Sagonas, T. Swift, and D.S. Warren. The limits of fixed-order computation. In International Workshop on Logic and Databases. LNAI: Springer-Verlag, 1995.

....Broadly, a program uses stratified negation whenever there is no recursion through negation. Refining this intuition can lead to an array of stratification classes. While XSB evaluates all programs, whether stratified or not, its evaluation is especially efficient for LRD stratified programs [20], which we now explain. Consider a simple approach to incorporate negation into tabling, and assume, to avoid complications of floundering, that the entire program is ground that no clause of the program contains any variable. Then if all predicates for negative literals are tabled, we could ....

....comes from the fixed order in which the evaluation selects literals in the body. The adjective dynamic arises from the fact that run time information is central to whether the derivation path remains suspended or not. LRD stratified programs and their evaluation method are explained in detail in [20, 16]. However, the following simple program is LRD stratified, but does not fit into other stratification classes (e.g. the more familiar class of (left to right) modularly stratified programs [18] p: q, r, s. q: r, p. r: p, q. s: p, q, r. Before leaving the subject of stratification, we ....

K. Sagonas, T. Swift, and D.S. Warren. The limits of fixed-order computation. In International Workshop on Logic and Databases. LNAI: Springer-Verlag, 1995.

....for locally stratified preference logic programs that have finite PTSLD search trees. The method described here is an extension of tabling, and, using the usual methods for proving completeness for tabled resolution, can be shown complete for programs that are left to right dynamically stratified [7] over optimization predicates, and to terminate for programs with the bounded term depth property [11] 6.1 The Commercial Viability of Logic based Standardization There are other commercial products that standardize names and addresses besides the logic based standardizers described in this ....

K. Sagonas, T. Swift, and D. Warren. The limits of fixed-order computation. In International Workshop on Logic and Databases. LNAI: Springer-Verlag, 1995.

....whenever there is no recursion through negation. Refining this intuition based on predicates, ground) atoms or modules can lead to a variety of stratification classes. While XSB evaluates all programs, whether stratified or not, its evaluation is especially efficient for LRD stratified programs [20], which we now explain. Consider a simple approach to incorporate negation into tabling, and assume, to avoid complications of floundering, that the entire program is ground; i.e. that no clause of the program contains variables. Then, if all predicates for negative literals are tabled, we could ....

....path is failed, while if A is determined to be completely evaluated with no answers, A is removed from the derivation path which then resumes its computation. Informally, if a program can be evaluated using the method sketched above it is called LRD stratified(formal definitions are provided in [20]) The adjective left to right comes from the computation rule. The adjective dynamic arises from the fact that run time information about the truth value of atoms is central to whether the derivation path remains suspended or not. The following simple program is LRD stratified, but does not ....

K. Sagonas, T. Swift, and D. S. Warren. The Limits of Fixed-Order Computation. In Proceedings of the First International Workshop on Logic in Databases, number 1154 in LNCS, pages 343--363, Italy, 1996. Springer-Verlag.

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