Semantics and expressiveness issues in active databases (1995)

by P Picouet, V Vianu
Venue:In ACM Symposium on Principles of Database Systems
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Relational Transducers for Electronic Commerce

by Serge Abiteboul, Victor Vianu, Brad Fordham, Yelena Yesha - JCSS , 1998
"... Electronic commerce is emerging as one of the major Websupported applications requiring database support. We introduce and study high-level declarative specifications of business models, using an approach in the spirit of active databases. More precisely, business models are specified as relational ..."
Abstract - Cited by 81 (12 self) - Add to MetaCart
Electronic commerce is emerging as one of the major Websupported applications requiring database support. We introduce and study high-level declarative specifications of business models, using an approach in the spirit of active databases. More precisely, business models are specified as relational transducers that map sequences of input relations into sequences of output relations. The semantically meaningful trace of an input-output exchange is kept as a sequence of log relations. We consider problems motivated by electronic commerce applications, such as log validation, verifying temporal properties of transducers, and comparing two relational transducers. Positive results are obtained for a restricted class of relational transducers called Spocus transducers (for semi-positive outputs and cumulative state). We argue that despite the restrictions, these capture a wide range of practically significant business models. 1 Introduction Electronic commerce is emerging as a major Web-s...

Active Views for Electronic Commerce

by S. Abiteboul, B. Amann, L. Mignet, S. Cluet , A. Eyal, L. Mignet, T. Milo , 1999
"... Electronic commerce is emerging as a major Web-supported application. In this paper we argue that database technology can, and should, provide the backbone for a wide range of such applications. More precisely, we present here the ActiveViews system, which, relaying on an extensive use of database ..."
Abstract - Cited by 54 (10 self) - Add to MetaCart
Electronic commerce is emerging as a major Web-supported application. In this paper we argue that database technology can, and should, provide the backbone for a wide range of such applications. More precisely, we present here the ActiveViews system, which, relaying on an extensive use of database features including views, active rules (triggers), and enhanced mechanisms for notification, access control and logging/tracing of users activities, provides the needed basis for electronic commerce. Based on

Verification of Relational Transducers for Electronic Commerce

by Marc Spielmann - JCSS , 2000
"... Motivated by recent work of Abiteboul, Vianu, Fordham, and Yesha [3] we investigate the verifiability of transaction protocols specifying the interaction of multiple parties via a network, where each party is equipped with an (active) database that participates in the interaction. Such transaction p ..."
Abstract - Cited by 41 (0 self) - Add to MetaCart
Motivated by recent work of Abiteboul, Vianu, Fordham, and Yesha [3] we investigate the verifiability of transaction protocols specifying the interaction of multiple parties via a network, where each party is equipped with an (active) database that participates in the interaction. Such transaction protocols typically occur in the context of electronic commerce applications and can be formalized as relational transducers. We introduce a class of powerful relational transducers based on Gurevich's abstract state machines and show that several verification problems related to electronic commerce applications can be solved for these transducers. Our approach is, in some sense, complementary to the approach in [3].

On Active Deductive Databases: The Statelog Approach

by Georg Lausen, Bertram Ludäscher, Wolfgang May - IN TRANSACTIONS AND CHANGE IN LOGIC DATABASES , 1998
"... After brie y reviewing the basic notions and terminology of active rules and relating them to production rules and deductive rules, respectively, we survey a number of formal approaches to active rules. Subsequently, we present our own state-oriented logical approach to active rules which combines ..."
Abstract - Cited by 29 (2 self) - Add to MetaCart
After brie y reviewing the basic notions and terminology of active rules and relating them to production rules and deductive rules, respectively, we survey a number of formal approaches to active rules. Subsequently, we present our own state-oriented logical approach to active rules which combines the declarative semantics of deductive rules with the possibility to de ne updates in the style of production rules and active rules. The resulting language Statelog is surprisingly simple, yet captures many features of active rules including composite event detection and di erent coupling modes. Thus, it can be used for the formal analysis of rule properties like termination and expressive power. Finally, we showhow nested transactions can be modeled in Statelog, both from the operational and the model-theoretic perspective.
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A Formal Semantics for Composite Temporal Events in Active Database Rules

by Iakovos Motakis, Carlo Zaniolo - Journal of Systems Integration , 1995
"... A major thrust of current research in active databases is allowing complex patterns of temporal events to serve as preconditions for rule triggering. Currently, there is no common formalism for specifying the semantics of composite events specification languages and different systems use an assor ..."
Abstract - Cited by 24 (0 self) - Add to MetaCart
A major thrust of current research in active databases is allowing complex patterns of temporal events to serve as preconditions for rule triggering. Currently, there is no common formalism for specifying the semantics of composite events specification languages and different systems use an assortment of approaches including Finite State Machines, Petri Nets and Petri Nets. In this paper, we propose a unifying approach, which is based on a syntax-directed translation of the composite event expressions into Datalog 1S , whose formal semantics is then used to define the meaning of the original event expressions.
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Decidability and Undecidability Results for the Termination Problem of Active Database Rules

by James Bailey, Guozhu Dong, Kotagiri Ramamohanarao - In Proceedings of the 17th ACM SIGMOD-SIGACT-SIGART Symposium on Principles of Database Systems , 1998
"... Active database systems enhance the functionality of traditional databases through the use of active rules or `triggers'. One of the principal questions for such systems is that of termination - is it possible for the rules to recursively activate one another indefinitely, given an initial trig ..."
Abstract - Cited by 19 (8 self) - Add to MetaCart
Active database systems enhance the functionality of traditional databases through the use of active rules or `triggers'. One of the principal questions for such systems is that of termination - is it possible for the rules to recursively activate one another indefinitely, given an initial triggering event. In this paper, we study the decidability of the termination problem, our aim being to delimit the boundary between the decidable and the undecidable. We present two families of rule languages, the one literal languages where each update is permitted to have just one atom in its body, and the unary languages where only unary relations may be updated, but higher arity relations may be accessed through views. Within each of these, we identify members close to the boundary of (un)decidability. Our context is similar to the while query language and the dynamics gives an interesting contrast to Datalog with negation; our results shed insights on the power of triggers as well as comparison of the termination problem to boundedness and query containment.
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On detecting conflict between proposed updates

by Michael Doherty, Richard Hull, Marcia Derr, Jacques Durand - IN PROC. OF INTL. WORKSHOP ON DATABASE PROGRAMMING LANGUAGES , 1995
"... In the Heraclitus paradigm, a delta value or more simply, delta, is a concrete value that corresponds to a difference between database states. This paper presents the Heraclitus [OO] (abbreviated H2O) DBPL, which provides a syntax and semantics for working with deltas in the context of object-orient ..."
Abstract - Cited by 11 (5 self) - Add to MetaCart
In the Heraclitus paradigm, a delta value or more simply, delta, is a concrete value that corresponds to a difference between database states. This paper presents the Heraclitus [OO] (abbreviated H2O) DBPL, which provides a syntax and semantics for working with deltas in the context of object-oriented databases.The paper also considers the use of deltas in connection with detecting conflict between pairs of proposed updates to a database. This is useful in contexts where multiple users are each creating and choosing between multiple possible updates. A semantically based notion of potential conflict between proposed updates is developed, along with several conservative approximations based on the use of different kinds of delta.
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Formal Characterizations of Active Databases: Part II

by Chitta Baral, Jorge Lobo, Goce Trajcevski , 1997
"... . This paper presents a formal framework for specifying active database systems. Declarative characterization of active databases allows additional flexibility in defining an implementation--independent semantics of the active rules. By making a clear distinction between actual and hypothetical exec ..."
Abstract - Cited by 9 (2 self) - Add to MetaCart
. This paper presents a formal framework for specifying active database systems. Declarative characterization of active databases allows additional flexibility in defining an implementation--independent semantics of the active rules. By making a clear distinction between actual and hypothetical execution of the actions, one can make claims and about the (possible) effects of an actions' sequence and prove them, without actually executing it. The results that we present extend the active database description language introduced in [5] with additional semantic dimensions. We demonstrate through examples how we can encode the active rules and their operational behavior from different existing systems. 1 Introduction and Motivation The core concept which makes a database system active is the concept of an active rule. The origin of the active rules is the production rule paradigm from the field of Artificial Intelligence with the languages like OPS5 [7], used in expert systems. Typically,...
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Expressiveness and Complexity of Active Databases

by Philippe Picouet, Victor Vianu - 6th Intl. Conference on Database Theory (ICDT), number 1186 in LNCS , 1997
"... . The expressiveness and complexity of several active database prototypes are formally studied. First, a generic framework for the specification of active databases is developed. This factors out the common aspects of the prototypes considered, and allows studying various active database features in ..."
Abstract - Cited by 5 (0 self) - Add to MetaCart
. The expressiveness and complexity of several active database prototypes are formally studied. First, a generic framework for the specification of active databases is developed. This factors out the common aspects of the prototypes considered, and allows studying various active database features independently of any specific prototype. Furthermore, each of the prototypes can be specified by specializing certain parameters of the framework. The prototypes considered are ARDL, HiPAC, Postgres, Starburst, and Sybase. Using their formal specifications, the prototypes are compared to each other with respect to expressive power. The results provide insight into the programming paradigm of active databases, the interplay of various features, and their impact on expressiveness and complexity. 1 Introduction The ability of a database to react to specified events is an increasingly common requirement in advanced database systems. This has led to the emergence of active databases, which provide...

Reactive maintenance of continuous queries

by Goce Trajcevski, Peter Scheuermann - ACM SIGMOBILE Mobile Computing and Communications Review
"... This work addresses the problem of maintaining the consistency of the answers to continuous queries which are posed by the users of the Moving Objects Databases (MOD). Assuming that the motion of the object is represented by a trajectory, we focus on the effect that the modifications to the trajecto ..."
Abstract - Cited by 3 (1 self) - Add to MetaCart
This work addresses the problem of maintaining the consistency of the answers to continuous queries which are posed by the users of the Moving Objects Databases (MOD). Assuming that the motion of the object is represented by a trajectory, we focus on the effect that the modifications to the trajectory data can have on the queries answer-set. In case a mobile user enters a road section in which an accident has occurred, which was not anticipated in the “expected ” traffic behavior, not only his trajectory needs to updated, but the answer to the query that he posed may need to be recalculated and transmitted again. In this work we propose a framework which enables detecting and processing the pending queries whose answers need to be re-evaluated upon modifications to the MOD. We identify the relevant syntactic elements which can be extracted from the user’s queries and we analyze their semantic implications. We also propose an architecture of a system that can be used for this task. We demonstrate how triggers can be used to maintain the answers to the users ’ queries “up to date ” with respect to the modifications to the MOD and we show that our framework can be implemented on top of the existing ORDBMS. I.
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