D. Montesi. A Model for Updates and Transactions in Deductive Databases. PhD Thesis, Universit& di Pisa, Dipartimento di Informatica, TD-20/93, 1993.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....semantics 2 XY STRATIFICATION AND NONDETERMINISM 3 is given in terms of F structures, and a notion of object identifier is modeled by way of existential quantification. As far as the dynamic aspects are concerned, there are proposals which provide a procedural semantics, as in the case of [Mon93, BGM95], and other proposals provide adhoc model theoretic semantics related to modal logic [BK93, MW86, Man89, Che91] In the former case, a poor integration of the various aspects is achieved, whereas in the latter a close relationship to real computing is missing. Moreover, it is difficult to combine ....

D. Montesi. A Model for Updates and Transactions in Deductive Databases. PhD thesis, Dipartimento di Informatica Universit`a di Pisa, 1993.

....emerged: to unify the different paradigms under a common semantics (often by using compilative techniques) 7, 20, 23, 27, 33] or to integrate specific semantics [11] In this paper, we follow the latter approach. We present an integration of deductive and active databases by extending U Datalog [5, 22] with a support for active rules in the style of the PARK semantics [14] we call the resulting language Active U Datalog. U Datalog is an extension to Datalog supporting declarative specification of updates based on a nonimmediate update semantics. U Datalog is well suited to such an extension ....

....syntax of Active U Datalog, and in section 4 its semantics. Section 5 shows in which sense Active U Datalog is an extension of U Datalog. Some final remarks follow. 2 Overview of U Datalog and Active U Datalog We present here an overview of U Datalog and we refer the reader to section 5 or to [22] for a complete description. Let us consider pairwise disjoint sets of constants Sigma, predicate names Pi and variables V . Terms 5 range over Sigma [ V and predicates are defined as usual on Pi. Pi is divided into two disjoint sets: extensional ( Pi e ) and intensional ( Pi i ) ....

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D. Montesi. A Model for Updates and Transactions in Deductive Databases. PhD thesis, Dipartimento di Informatica -- Universit`a di Pisa, 1993.

....different from the language used for describing rules, making transaction optimization difficult [13] To overcome these drawbacks we use a new approach to integrate declarative query language and updates, modeling transactions. The language we use is U Datalog. The basic idea of U Datalog [5, 20] is that (extensional) updates are not executed as soon as they are evaluated. Rather, they are collected and are executed only at the end of the query answering process. Updates, due to the non immediate semantics, are expressed in a declarative way by using constraints, that is p(a) states that ....

....a bottom up interpretation of rules with updates has no meaning. By contrast, the two phases semantics given to U Datalog removes this drawback. For it, both a top down and a bottom up computational model can be defined. In the following we recall the language and its informal semantics (see [20] for a complete description) In that, we will assume the reader familiar with the basic notions of logic programming [3] We consider pairwise disjoint sets of constants Sigma, predicate names Pi and variables V . Predicates have a certain arity. A term is either a constant or a variable. The ....

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D. Montesi. A Model for Updates and Transactions in Deductive Databases. PhD thesis, Dipartimento di Informatica, University of Pisa, March 1993.

....way. A first class of proposals tackle only static (structural) aspects. This is the case, for example, of LOGIN [4] or of its extension F logic [12] As far as the dynamic aspects are concerned, there are various proposals, which provide a procedural or declarative semantics, as in the case of [16, 7, 8]. In either cases, static and dynamic aspects are dealt with in separate frameworks. On the contrary, we argue in [10] that Datalog provides a flexible uniform framework, and moreover enables us to handle sophisticated dynamic features, such as roledynamics and object migration, widely ....

D. Montesi. A Model for Updates and Transactions in Deductive Databases. PhD thesis, Dipartimento di Informatica Universit`a di Pisa, 1993.

.... updates on the same fact) U Datalog was tailored to the need of keeping many of the already results and techniques developed for Datalog, specifically efficient query eval uation strategies [11] expressive power [5] and the nice collect execute model which nicely fits into a transaction model [53]. The language we propose in this paper (called Obj U Datalog) is based on the notion of deductive object. Each object is an U Datalog database. Each object has a state (a set of facts) and a set of methods (expressed through rules) Methods may also contain update atoms to modify the object ....

....in DLP [47] D [54] Tq [20] end DL [5] updetes ere executed es soon es they ere evelueted. This epproech leeds to complex sementics end to computetions performed in e sequence of stetes 12 instead of in a single one. In the following we recall the language and its informal behavior (see [53] for a complete description) We consider pairwise disjoint sets of constants E, predicate names II and variables V. Predicates have a certain arity. A term is either a constant or a variable. The atoms are expressions of the form p(t, t) where the ti, 1 i n, are terms and p is a ....

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D. Montesi. A Model for Updates and Transactions in Deductive Databases. PhD Thesis, Universit& di Pisa, Dipartimento di Informatica, TD-20/93, 1993.

....By contrast in DLP [25] LDL [30] and DL [3] updates are executed as soon as they are evaluated. This approach leads to complex semantics and to computations performed in a sequence of states instead of in a single one. In the following we recall the language and its informal behavior (see [29] for a complete description) We consider pairwise disjoint sets of constants Sigma, predicate names Pi and variables V . Predicates have a certain arity. A term is either a constant or a variable. The atoms are expressions of the form p(t 1 ; t n ) where the t i ; 1 i n, are terms ....

....explicit context switches i.e. requests for the evaluation of a subquery sent to another object. Note that each object consists of a time varying component (its state) and a time invarying one (its methods) Therefore, the semantics of an object should be given in a compositional way (as done in [29] for U Datalog) We do not consider this level of composition here, because each object regards the others as single units, being not interested in the subdivision between extensional and intensional components. In this phase we regard an Obj U Datalog program as a tuple of logic databases. The ....

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D. Montesi. A Model for Updates and Transactions in Deductive Databases. PhD thesis, Dipartimento di Informatica, Universit`a di Pisa, March 1993.

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