Balbin, I., Port, G.S. and Ramamohanarao, K. Magic set computations for stratified databases. Technical Report 87/3, Department of Computer Science, University of Melbourne, 1987. 42  Home/Search   Document Not in Database   Summary   Related Articles   Check

....or the cut, or programs containing negation. The approach can be used to evaluate some stratified programs containing negation, and we refer the reader to ################ This work was supported in part by an IBM Faculty Development Award and NSF grant IRI 8804319. 2 [BNRST87] [BPR87]. We believe that both Prolog style evaluation and bottom up approaches have their own advantages and are likely to be preferable in certain important domains. In this paper, we show the power of the bottom up approach, and, by a careful separation of binding propagation and the flow of control ....

I. Balbin, G.S. Port, and K. Ramamohanarao, "Magic Set Computation of Stratified Databases," Technical Report 87/3, University of Melbourne, 1987.

....( 1] used the term standard semantics ) for such programs that captures their intended meaning. However, the magic sets transformation of a stratified program may not be stratified, and several authors have considered the problem of extending magic sets to stratified programs. The approach of [2, 3] involves relabeling some predicates, while [4, 9, 10] sequence the execution of rules in the bottom up computation. Kolaitis [11] showed that there are several interesting logic programs that are not stratifiable but for which a natural semantics exists. This points out the need to efficiently ....

....of a stratified program that becomes unstratified after magic transformation is given in Section 5. The problem of evaluating an unstratified magic program (obtained from a stratified program) has received considerable attention. Among the techniques to solve the problem are: predicate labelling [2, 3], a magic sets interpreter [4] rule ordering [9] and weak stratification [10] As a consequence of the following result we have that any procedure for computing well founded models can overcome the difficulties that arise when a magic sets transformation of a stratified program creates an ....

Balbin, I., Port, G.S. and Ramamohanarao, K. Magic set computations for stratified databases. Technical Report 87/3, Department of Computer Science, University of Melbourne, 1987.

....stratified since path bb depends on magic path bb which in turn depends on :path bb . 3 The problem of evaluating an unstratified magic program (obtained from a stratified program) has received considerable attention. Among the techniques to solve the problem are: predicate labelling [2, 3], a magic sets interpreter [4] rule ordering [10] and weak stratification [25] As a consequence of the following result we have that any procedure for computing well founded models can overcome the difficulties that arise when a magic sets transformation of a stratified program creates an ....

Balbin, I., Port, G.S. and Ramamohanarao, K. Magic set computations for stratified databases. Technical Report 87/3, Department of Computer Science, University of Melbourne, 1987.

....problem with bottom up computation is that it does not naturally make use of ground terms in a literal in the same goal driven way that a top down computation does. A direct consequence is that many irrelevant facts may be generated during a bottom up computation. The magic set approach [3, 6, 15, 5, 1] to deductive databases performs a compile time transformation of the database, based on the query, into an equivalent form that enables a bottom up computation to focus on the relevant tuples. The magic set solution is well suited to exploiting ground information in computing relevant facts. A ....

....program in figure 1 Clearly, since both X and Y are expected to be bound, the comparison X Y will not cause an infinite computation in the first rule. The definition of safety with respect to a query follows naturally using the same intuition as that for allowedness with respect to a query in [1]. This definition presumes that each constraining predicate has an associated predetermined set of safe adornments. For example, the only safe adornment of is bb . Definition 2.4. The limited variables for a given adorned rule are defined as follows: 1. Variable X is limited if it appears ....

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I. Balbin, G. Port, and K. Ramamohanarao. Magic set computation for stratified databases. Technical Report 87/3 (Revised), Department of Computer Science, University of Melbourne, Australia, 1987. To appear in the Journal of Logic Programming.

....this progress took the form of the development of evaluation algorithms and rule rewriting techniques that can increase the speed of bottom up computation of answers to queries by several orders of magnitude. These techniques, which include differential or semi naive evaluation [3, 4] magic sets [1, 5, 7, 17], the Alexander method [11, 15] counting sets [16, 17] rule rectification [19] and constraint propagation [9] generally work by reducing the number and or the size of the tuples one must generate to answer a given query. In two other recent papers ( 13] and then [12] J. Naughton, R. ....

Balbin, I., Port, G., and Ramamohanarao, K. Magic set computation for stratified databases. Tech. Rep. 87/3 (revised), Department of Computer Science, University of Melbourne, Australia, 1987. To appear in the Journal of Logic Programming.

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Balbin, I., Port, G.S. and Ramamohanarao, K. Magic set computations for stratified databases. Technical Report 87/3, Department of Computer Science, University of Melbourne, 1987. 42

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