S.Gatzin, A.Geppert and K.R.Dittrich, "Integrating Active Concepts into an Object-Oriented Database System", Proc 3rd International Workshop on database programming languages, Nafplion, 1991.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....Rgles Actives, lvnements primitifs et composites, Dtection d vnements. 1 Introduction In this paper, we are interested in events in active databases. Such databases are becoming popular and many research projects concern this area [12, 23, 17, 23, 29] also many prototypes have been developed [27, 30, 15, 22, 8, 2]. Event models and languages have received a lot of attention [18, 26, 16, 14, 5] Events are either considered as points in time [16, 14] or as happening of interest occurring at specific points in time [18] Events may be primitive (e.g. the update of Bobs salary) or composite, i.e. comprised ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating active concepts into an object- oriented database system. In Proc. of the 3rd Int. Workshop on Database Programming Languages: Bulk Types 4 Persistent Data, pages 399-415, Nafplion - Greece, 1991. Morgan Kaufmann.

....rule concept. References: BBKZ92] BBKZ93] BZBW95] BB95] 2.15 SAMOS SAMOS is a project at the University of Zurich, Switzerland. While aiming at the HiPAC functionality, it has a rich language comparable to ODE (2.13) A prototype is implemented on top of ObjectStore. References: GGD91] GD92] GD93a] GD93b] GD94] GGD95a] Secondary: PDW 93] TGD95] 2.16 Sentinel Sentinel is a project at the University of Florida, Database Systems Research and Development Center, Gainesville, Florida. It developed directly from results obtained in the HiPAC project. Several ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating active concepts into an object-oriented database system. In 3rd Int'l.Workshop on Database Programming Languages, Naflion, August 1991. Annotation: This paper introduces the basic concepts of the SAMOS project. It is a good description of the utilization of object-oriented features for active rules.

....2.13 SAMOS SAMOS is a project at the University of Zurich, Switzerland. While aiming at the HiPAC functionality, it has a rich language comparable to ODE (2.11) A prototype was based on GemStone OODB. GD93a] and [GD94] mention a new prototype implementation on top of ObjectStore. References: GGD91] GD92] GD93a] GD93b] GD94] 3 SPECIAL ISSUES 4 2.14 Sentinel Sentinel is a project at the University of Florida, Database Systems Research and Development Center, Gainesville, Florida. It developed directly from results obtained in the HiPAC project. Several papers discuss prototypes ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating active concepts into an object-oriented database system. In 3rd Int'l.Workshop on Database Programming Languages, Naflion, August 1991. Annotation: This paper introduces the basic concepts of the SAMOS project. It is a good description of the utilization of object-oriented features for active rules.

....of its transition predicate occurs and the ECA rule s precondition evaluates to true. That is to say, an ECA rule consists of events, conditions and actions. The semantics of an ECA rule is that when the event occurs, evaluate the condition; if the condition is true, then execute the action(s) [10]. Characteristics of ECA rules and their collective behaviour in both relational and object oriented database systems have been analysed by various researchers and are now well known [4, 24] ECA rules have been used for database system extensions like supporting integrity constraints, for closed ....

Gatziu E, Geppert A, Dittrich K R (1991). Integrating active concepts into an object-oriented database system. In: 3 rd International Workshop on Database Programming Languages, Naphlion, Greece.

....section 4 describes in detail the production rule compilation scheme, while section 5 briefly sketches incremental rule matching. Finally, section 6 discusses various implementation issues and section 7 concludes the paper. 2. Related Work Several active OODB systems have been developed so far [8, 11, 13, 20]. Traditionally OODB systems incorporate ECA rules only, since event driven rules conform to the message driven nature of OODB programming languages. Potential event is every recognisable message method and rule triggering can be easily implemented as a detour from normal method execution. ....

Gatziu, S, Geppert, A and Dittrich, K R, Integrating active concepts into an object-oriented database system, in: Kanellakis, P and Schmidt, J W, eds., Proc. 3rd Workshop on Database Programming Languages, Morgan-Kaufmann, 1991, 399-415.

....features of E DEVICE; Section 7 discusses the system performance, presenting results for deductive rules; and finally, section 8 concludes this paper with a summary of the main points and a discussion of future work. 2. Related Work There are several active OODB systems that support ECA rules [9, 10, 12, 11, 15]. The ECA rule type is the most easy to implement in OODBs since events conform to the message passing paradigm of OO computation and every recognizable message method can be a potential event. Therefore, they can be executed as a detour from normal method execution. There are a few active OODB ....

S. Gatziu, A. Geppert, and K.R. Dittrich, " Integrating active concepts into an object-oriented database system," Proc. Workshop on Database Programming Languages, Morgan-Kaufmann, Nafplion, Greece, 1991, pp. 399415.

....with various optimizations, and section 8 presents some performance results. Finally, section 9 concludes this paper with a summary of the main points and a discussion of future work. 2. Rule Integration in Active Databases Several active database systems have appeared in the literature so far [10, 12, 14, 21, 22, 28, 29, 38, 44]. All of them incorporate the active rule facility which allows one to provide automatic execution of database operations in response to certain events and or conditions. There is a certain confusion about the term active rules ; some researchers [28, 29] denote by this term the production rules ....

....database operations in response to certain events and or conditions. There is a certain confusion about the term active rules ; some researchers [28, 29] denote by this term the production rules met in expert system technology [17, 18] while others refer to the Event Condition Action (ECA) rules [10, 12, 14, 21] met in many active database systems. To avoid the confusion we will explicitly use the above terms interchangeably with the term data driven for the production rules, i.e. the rules of the form: #FRQGLWLRQ#7 (1#DFWLRQ because these rules describe data states that should be reached in order ....

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S. Gatziu, A. Geppert and K.R. Dittrich, Integrating active concepts into an object-oriented database system, Proc. 3rd Workshop on Database Programming Languages, Nafplion, Greece, Morgan-Kaufmann (1991) 399-415.

....are based on the query language of the underlying database system, and thus support declarative expression of conditions and straightforward facilities for performing updates. Such systems generally have simple event specification languages and execution models. Active object oriented databases [12, 17, 11, 6], which are based on the programming language of the underlying database system, and thus support procedural mechanisms for the expression of conditions and for performing updates. Such systems generally have sophisticated event specification languages and execution models. However, the trend ....

....are based on the query language of the underlying database system, and thus support declarative expression of conditions and straightforward facilities for performing updates. Such systems generally have simple event specification languages and execution models. Active object oriented databases [12, 17, 11, 6], which are based on the programming language of the underlying database system, and thus support procedural mechanisms for the expression of conditions and for performing updates. Such systems generally have sophisticated event specification languages and execution models. However, the trend ....

S. Gatziu, A. Geppert, and K. Dittrich. Integrating active concepts into an objectoriented database system. In P. Kanellakis and J.W. Schmidt, editors, Proc. 3 rd Workshop on Database Programming Languages. Morgan-Kaufmann, 1991.

....that are executed automatically when certain conditions are met. They offer a flexible, unifying mechanism for common database management tasks, like constraint enforcement and view maintenance. As a consequence, a number of proposals for incorporating rules into DBMS s appeared recently [16, 4, 6, 3, 9, 5, 2, 11, 12]. The correct implementation of constraint enforcement and view maintenance based on rules requires that the set is confluent and terminates [15] A rule set terminates if its execution terminates on all database states. A terminating rule set is confluent if for each initial database state db 0 ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating active concepts into an object-oriented database system. In Proceedings of the 3th International Workshop on DBPL, pages 341--357, 1991.

....most important advantage of object orientation is the encapsulation of data and behaviour in one object. Rules are part of the behaviour of objects. They describe what actions triggered in specific situation. Examples of object oriented DBMSs that offer encapsulation of rules in objects are SAMOS [15] and Chimera [10] However, these systems offer a hybrid model. In both systems it is still possible to define rules separate from a class. Thus, we do not have a single place to look for the behaviour of an object. We take encapsulation to its extremes. All behaviour is encapsulated with an ....

....= M(S; I(fc (a)ja 2 Ag) 4. Related Research Active Databases An autonomous objects has active rules. Therefore a database of autonomous objects is an active database. Some active DBMSs have been constructed using the relational model [16, 25] Others are based on an object oriented data model [15, 12]. In most systems there is a separate rulebase, where all rules are stored. In an object oriented system this rulebase can be integrated with the database [13, 14] in such a way that rules can be treated as objects themselves. A object oriented system would offer the possibility of defining a rule ....

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Stella Gatziu, Andreas Geppert, and Klaus R. Dittrich. Integrating active concepts into an object-oriented database system. In Paris Kanellakis and Joachim W. Schmidt, editors, The Third International Workshop on Database Programming Languages: Bulk Types and Persistent Data, pages 399-415, San Mateo,. CA, USA, August 1991. Morgan Kaufmann.

....2.13 SAMOS SAMOS is a project at the University of Zurich, Switzerland. While aiming at the HiPAC functionality, it has a rich language comparable to ODE (2.11) A prototype was based on GemStone OODB. GD93a] and [GD94] mention a new prototype implementation on top of ObjectStore. References: GGD91] GD92] GD93a] GD93b] GD94] Secondary: PDW 93] 2.14 Sentinel Sentinel is a project at the University of Florida, Database Systems Research and Development Center, Gainesville, Florida. It developed directly from results obtained in the HiPAC project. Several papers discuss ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating active concepts into an object-oriented database system. In 3rd Int'l.Workshop on Database Programming Languages, Naflion, August 1991.

....that executes concurrently with the triggering transaction. The same modes are available for C A coupling, which specifies the relationship between condition evaluation and action execution. 2. 2 SAMOS The overall goal of SAMOS (Swiss Active Mechanism Based Object Oriented Database System) [Gatz91, Gatz92, Gatz94] is the combination of active and objectoriented characteristics within one coherent system by means of a layered approach. Since current OODBS differ in their data models and functionalities only characteristic properties provided by almost all OODBS, like inheritance, user definable types and ....

S. Gatziu, A. Geppert, K.R. Dittrich, Integrating Active Concepts into an Object-Oriented Database System, Proc. of the 3rd Int. Workshop on Database Programming Languages, Nafplion, August 1991

.... Ramamritham, 1987) In general, these assumptions are not applicable in the type of complex environments that characterize the next generation of real time systems (Stankovic, 1988b) Considerable research has been made on reactive databases, e.g. Chakravarthy, 1989; Gehani and Jagadish, 1991; Gatziu et al. 1991), and also real time databases, e.g. Singal, 1988) but results on reactive real time databases are limited to discussion in a few research projects, e.g HiPAC (Chakravarthy et al. 1989) and REACH (Buchmann et al. 1992) In the HiPAC report, active databases and time constrained databases are ....

Gatziu, S., Geppert, A., and Dittrich, K. (1991). Integrating active concepts into an objectoriented database system. In Proc. Third Int'l Workshop on Database Programming Languages (DBPL), Nafplion, Greece.

.... When object oriented database systems [ADM 89] were developed, projects on integrating reactive behavior into such systems emerged, the most comprehensive being HiPAC [CBB 89] which was followed by several projects such as Sentinel [Cha89, CM91] from University of Florida, and SAMOS [GGD91, GD92] developed at Universitat Zurich. Other active OODBMSs are Ode [GJ91, GJ92, GJS92a] from AT T, ADAM [Pat89] REACH [BBKZ93] from Technical University of Darmstadt, which also includes real time behavior, and ACOOD [Ber91] and DeeDS [AHEM94, AHE 96] from University of Skovde. All of the ....

Stella Gatziu, Andreas Geppert, and Klaus R. Dittrich. Integrating active concepts into an object-oriented database system. Proceedings on the Third International Workshop on Database Programming Languages (DBPL), Nafplion, Greece, August 1991.

....1991] Stonebraker et al. 1990] Stonebraker and Kemnitz 1991] Delcambre and Etheredge 1988] Widom et al. 1991] Widom and Finkelstein 1990] Beeri and Milo 1991] Cohen 1989] Diaz et al. 1991] Kotz et al. 1988] Schreier et al. 1991] Simon et al. 1992] Buchmann 1990] E. Anwar 1993] S. Gatziu 1991] In this chapter, we will illustrate the features of active database systems using Ariel [Hanson 1992] HiPAC [Chakravarthy et al. 1989, Dayal et al. 1988, McCarthy and Dayal 1989] POSTGRES [Stonebraker et al. 1990, Stonebraker and Kemnitz 1991] and Starburst [Widom et al. 1991, Widom and ....

....describing run time rule processing in HiPAC, it is necessary to introduce the concept of coupling modes. Coupling modes originated in the HiPAC project but subsequently have been discussed in the context of other active database systems, e.g. Gehani and Jagadish 1991, Schreier et al. 1991, S. Gatziu 1991, E. Anwar 1993, Buchmann 1990] Coupling modes determine how rule events, conditions, and actions relate to database transactions. Whereas in Ariel, POSTGRES, Starburst, and many other active database systems, rule conditions are evaluated and actions are executed in the same transaction as the ....

S. Gatziu, A. Geppert, K. D. (1991). Integrating active concepts into an objectoriented database systems. In Proceedings of the Third International Workshop on Database Programming Languages.

....be required to express the same functionality as a single production rule. Thus systems which support only ECA rules may provide cumbersome solutions to certain tasks which have been felt to be important applications of active functionality. While many proposals have been made for active OODBs [13, 22, 17, 12, 29], none of these support production rules. There thus seems to be a need for work on the integration of production rule facilities with OODBs. This paper addresses two issues of relevance to this task the way in which such functionality can be implemented, and the performance which can be ....

S. Gatziu, A. Geppert, and K. Dittrich. Integrating active concepts into an object-oriented database system. In P. Kanellakis and J.W. Schmidt, editors, Proc. 3 rd Workshop on Database Programming Languages. Morgan-Kaufmann, 1991.

....extended model based methodology with notable flexibility in reuse. This paper shows its applicability to this area with a formal respecification of the Starburst active rule system. The specifica2 tion is structurally comparable with active rule system implementations in which rules are objects [7, 8, 11], with three important distinctions: 1. functionality inherited from the underlying system in the implementations is made overt here; 2. the Object Z specification is much more concise and readable than the implementations; 3. Object Z is amenable to formal reasoning, allowing for verification of ....

....environments for Petri nets (such as LOOPN from the University of Tasmania) There are some tools for analysis of nets, but they can only decide a limited range of questions about temporal phenomena. Petri nets have been employed in event specification formalisms for active databases; see [11]. 3.2.8 Process algebras These include CCS [29] CSP [18] and simpler calculi like path expressions and flow languages. These systems have not been used for large scale specifications, and are only modular in a limited sense (some form of compositionality holds for some of them) These systems ....

Stella Gatziu, Andreas Geppert, and Klaus Dittrich. Integrating active concepts into an objectoriented database system. In P. Kanellakis and J.W. Schmidt, editors, Proc. 3 rd Workshop on Database Programming Languages. MorganKaufmann, 1991.

.... Corporation of America (and later Xerox) which pioneered many of the features and techniques found in active databases today [DBM88] Other important object oriented systems include Ode, which uses finitestate automata to detect events [AG89] SAMOS, which uses Petri net based event detection [GGD91]; and Sentinel, which features a subscription scheme for linking events to rules [AMC93] A number of well developed active relational databases also exist, such as Postgres [SK91] Ariel [Han92] and Starburst [WF90] Many specific proposals have been made for using active databases in various ....

S. Gatziu, A. Geppert, K.R. Dittrich, "Integrating active concepts into an object-oriented database system," in 3rd International Workshop on Database Programming Languages, Naphlion, Greece (1991).

....GemStone. Concerning the underlying concepts of active object oriented database systems it is commonly accepted that the pioneering work of HiPAC [Daya88] in terms of its knowledge model and execution model has influenced a whole fleet of active object oriented database system proposals, e.g. [Anwa93, Chak90, Diaz91, Gatz91, Geha91, Kotz93, Mede91]. TriGS also builds on this work. Like in most systems the knowledge model of TriGS comprises Event Condition Action (ECA) rules. Unlike most systems, however, TriGS does not exploit coupling modes to describe the execution model of the rule scheduler. Instead, the event specification mechanism is ....

....continues evaluating the next condition. Finally, the Action Executor has to execute all actions still waiting for execution within the AEP dictionary according to the specified priorities and according to the specified transaction semantics. 5. Comparison and Outlook Almost all active systems [Daya88, Diaz91, Gatz91, Geha91, Mede91, Kotz93] use coupling modes to define CEPs and AEPs, which implies that the condition has to be evaluated either immediately after the signaled event ( immediate coupling) or at the end of the triggering transaction ( deferred coupling) or in a separate transaction ( separate coupling) The same ....

S. Gatziu, A. Geppert, K.R. Dittrich, Integrating Active Concepts into an Object-Oriented Database System, Proc. of the 3rd Int. Workshop on Database Programming Languages, Nafplion,

.... very powerful rule language for an object oriented data model, a flexible execution semantics, and several main memory experimental prototypes [20] Recently there has been an explosion of projects in object oriented active database systems many of these projects are still preliminary; see e.g. [3,4,6,7,10,11, 24,25,26,27,33,35]. Several previous papers have described language, implementation, or application development issues related to the Starburst Rule System. An initial proposal for the Starburst rule language appears in [49] 48] describes how the extensibility features of the Starburst prototype are used in ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating active concepts into an object-oriented database system. In Proceedings of the Third International Workshop on Database Programming Languages, Nafplion, Greece, August 1991.

.... combination of the above dimensions, has recently been proposed and inves 1 An expert database sysetm that uses deductive reasoning (backward chaining) is often referred to as a Deductive Database System [17] tigated, as exemplified by such prototypes systems as HiPac [13] ADAM [15] SAMOS [19], Ode [20, 22] Chimera [4] and Sentinel [8] A system taking such an approach allows a wide range of internal functions and external applications to be supported in a more general and extensible manner. Some of these systems are implemented by developing a totally new database kernel from ....

....22] Chimera [4] and Sentinel [8] A system taking such an approach allows a wide range of internal functions and external applications to be supported in a more general and extensible manner. Some of these systems are implemented by developing a totally new database kernel from scratch (e.g. [14, 15, 19, 22]) and others by building a special rule management module inside an existing OODBMS (e.g. 4, 8] However, this built in approach is system specific, rather than general purpose, as the specially implemented database kernel and or rule management module can not be (easily) used by different ....

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S. Gatziu, A. Geppert, and K.R. Dittrich. "Integrating active concepts into an object-oriented database system." In Proceedings of the 3rd Int'l Workshop on Database Programming Languages, pages 399--415, 1992.

.... The features of these systems depend upon whether the rules are defined for a general purpose DBMS or for specific applications [2] The approach proposed here is based on propositions done in the framework of the most representative object oriented projects: ODE [12, 13] O 2 [19] SAMOS [11] and HiPAC [9, 15, 18] We also considered works done on the execution model of rule systems in [14, 10, 8, 17, 23, 24, 6] The main contributions of our work are as follows: ffl Rules belong to a schema and thus can be used as any other component of a schema. Rules respect encapsulation and ....

....definitions. The execution of a rule takes place within an application and interacts with one or more databases. Rules are permitted to operate on objects and values 2 . We do not allow rules to be properties of a class because this implies the notion of external and internal rules as in [11] which can be confusing from the programmer s point of view. Rules respect encapsulation. This means that only authorized operations on objects or values can produce valid events. Such operations are public methods, programs or updates on values. By default values are public. When compiling rule ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating Active Concepts into an ObjectOriented Database System. In Proc of the 3rd International Workshop on Database Programming Languages: Bulk Types & Persistent Data, pages 399--415, Nafplion, 1991. Morgan Kaufmann.

.... Active object oriented concepts are especially useful in the area of nonstandard applications in order to express an event driven and constraint driven system environment [Chak90, Daya88b, Ahme92] Several attempts have been made to integrate active concepts into object oriented databases [Beer91, Daya88a, Diaz91, Gatz91, Geha91, Kim92, Mede91]. Current approaches to active objectoriented database systems, however, do not consider the various active concepts together with some of the basic object oriented concepts: They do not exploit all the advantages of object oriented features to make the whole system more expressive and open for ....

S. Gatziu, A. Geppert, K.R. Dittrich, Integrating Active Concepts into an ObjectOriented Database System, Proc. of the 3rd Int. Workshop on Database Programming Languages, Nafplion, August 1991

....based on the query language of the underlying database system, and thus support declarative expression of conditions and straightforward facilities for performing updates. Such systems generally have simple event specification languages and execution models. Active object oriented databases [12, 17, 11, 6], which are based on the programming language of the underlying database system, and thus support procedural mechanisms for the expression of conditions and for performing updates. Such systems generally have sophisticated event specification languages and execution models. However, the trend that ....

S. Gatziu, A. Geppert, and K. Dittrich. Integrating active concepts into an objectoriented database system. In P. Kanellakis and J.W. Schmidt, editors, Proc. 3 rd Workshop on Database Programming Languages. Morgan-Kaufmann, 1991.

.... our rule system we took into consideration works on database production rules which have focused on (i) relational systems: Postgres[36, 37, 38] Starburst[30, 35, 3] and Ariel[25, 26] and (ii) object oriented systems: HiPAC [16, 14, 15, 19, 27, 31, 12] Ode [22, 24, 23] O 2 [32] 3 , SAMOS [21], Sentinel [4] and TriGS [29] We also consider specific approaches for incorporating rules in software engineering environments: Marvel [7, 8, 9] ALF [33] and Adele [18, 11] The following provides a motivation for our approach based on the characteristics and limitations of the existing ....

....earlier work done in the framework of the O2 prototype and our rule system NAOS, we will refer to the prior as ProtoO2 . Event specification The event part of a rule specifies a type of events. These events are usually divided into two categories: primitives (called basics in Ode) and composites [19, 21, 24]. Three kinds of primitive events are considered: internal events related to database operations, temporal events and external events. Composite events are made up of other composite or primitive events. In HiPAC, SAMOS and Sentinel, events are mostly related to the state of objects and to the ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating Active Concepts into an ObjectOriented Database System. In Proc. of the 3rd International Workshop on Database Programming Languages: Bulk Types & Persistent Data, pages 399--415, Nafplion, 1991. Morgan Kaufmann.

....of several di#erent events, where an event algebra is used to specify the composition of events. HiPAC was one of the first active database projects to define an event algebra [Daya96] Notable projects involving composite MCC INSL 131 98 events since HiPAC include SNOOP [Chak97, Chak97] Samos [Gatz91, Gatz93, Gatz94] and Ode [Geha92a, Geha92b] Other projects include REACH [Bran93] and REFLEX [Naqv93, Naqv93] The work of Sistla and Wolfson has focused specifically on composite events involving temporal triggers [Sist95a, Sist95b] More recent e#orts have extended previous work on composite ....

S. Gatziu, A. Geppert, and K. Dittrich, "Integrating Active Concepts Into an ObjectOriented Database System," DBPL-3 Workshop, Greece, 1991.

....data and interpreted by an engine at runtime. Thus, it is possible to change or extend 2 system behavior dynamically by merely modifying existing rules or defining new rules. There exist different approaches aiming at the integration of active concepts with object oriented database systems [Anwa93, Chak90, Coll94, Diaz91, Gal95, Gatz91, Gatz95, Geha92, Kotz93, Mede91]. They mainly differ in the expressive power of their event specification languages, in the integration of the rule model with the underlying object oriented model, and in approaches for terminating rule execution. In general, the designer is confused with the power of the provided concepts and ....

S. Gatziu, A. Geppert, K.R. Dittrich, Integrating Active Concepts into an Object-Oriented Database System, Proc. of the 3rd Int. Workshop on Database Programming Languages, Nafplion, 1991

....of triggers. Secondly, it allows extension of the object oriented paradigm with (declarative) mechanisms to specify event driven behavior and constraints, both local to one object and global to a system of objects. Current approaches to integrating active facilities and object oriented systems [Gatz91, Geha91, Kim92, Kotz92, Mede91] do not fully reflect the semantics of object oriented concepts in the definition of triggers. This paper contributes toward filling this gap. TriGS ( Trigger system for GemStone) focuses on several design goals that originate both from shortcomings of existing active object oriented systems and ....

....Modes and Transactions On detection of an event, the rules of the respective triggers have to be fired. Thus their conditions have to be evaluated and their actions executed. When and where the condition evaluation and the action execution take place is determined by three different coupling modes [Daya88b, Gatz91], which are defined relative to the occurrence of the respective event and its surrounding transaction (called triggering transaction) immediate E C E A coupling The condition action has to be evaluated executed immediately after the occurrence of the event and within the triggering ....

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S. Gatziu, A. Geppert, K.R. Dittrich, Integrating Active Concepts into an Object-Oriented Database System, Proc. of the 3rd Int. Workshop on Database Programming Languages, Nafplion, August 1991

....2 fRelational, Extended Relational, Deductive, Object Orientedg Primitive, in which case the event is raised by a single, low level occurrence, which belongs to one of the categories described in Source below. Composite, in which case the event is raised by some combination of primitive events [5, 14]. A composite event is constructed from a number of other primitive or composite events using a range of operators which vary from system to system, but which may include conjunction, disjunction, sequence and negation. The semantics of composite events are complicated by the need to maintain a ....

....it is possible for the event to be raised before or after the execution of the operation. Transaction, in which case the event is raised at some specific point in a transaction (e.g. before abort, start of transaction) Clock, in which case the event is raised at some particular point in time [5, 14] (e.g. it is 23:00 hours, it is 4 hours since some other event) Furthermore, clock events can be used to specify the time limit within which composite events should take place [14] Error, in which case some error has occurred within the database. External, in which case the event is raised by ....

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S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating active concepts into an object-oriented database system. In Proc. of the 3rd Int. Workshop on Database Programming Languages, pages 399--415, August 1991.

....able to avoid these limitations by means of ECA rules. Rules provide a mechanism for an explicit, localized, and transparent specification of business policies. There exists quite a number of different approaches aiming at the integration of active concepts with object oriented database systems [Anwa93, Chak90, Coll94, Diaz91, Gal95, Gatz91, Geha92, Kotz93, Mede91]. They mainly differ in the expressive power of their event specification languages, in the integration of the rule model with the underlying object oriented model, and in approaches for terminating rule execution. In general, the designer is confused with the power of the provided concepts and ....

S. Gatziu, A. Geppert, K.R. Dittrich, Integrating Active Concepts into an Object-Oriented Database System, Proc. of the 3rd Int. Workshop on Database Programming Languages, Nafplion, 1991

....passive, i.e. they only react to explicit requests by users or applications. An active DBMS executes operations automatically whenever certain events occur and=or certain conditions are met. There already are quite a few proposals for the integration of active behavior into DBMS, e.g. Sto92] GGD91] Wid92] DNP91] and [GJ92] among many others. Most of these approaches use ECA rules which were first introduced by HiPAC ( DBM88] DD89] ECA means that if a certain Event occurs and a certain Condition is met, the DBMS automatically executes the specified Action. ECA rules can be used ....

S. Gatziu, A. Geppert, and K.R. Dittrich. Integrating active concepts into an object--oriented database system. In Proc. DBPL--3 workshop, August 1991.

....be a sub event type of the event of the original rule, though the meaning of subtyping for events is not presented. Similarly, there is no discussion of whether and how class spanning rules may be overridden in NAOS. In the SAMOS system, both class specific and class spanning rules are supported (Gatziu, Geppert Dittrich, 1991, Geppert, et al. 1995) Class specific rules (class internal rules in SAMOS terminology) can be encapsulated within the class and may not be visible to the user of the class. Events can be defined so that they have independent existence and can be reused in multiple rules. Class spanning rules ....

....of being well formed. If now another definition of Inform Operator is specified with the class vector Chemical, MXE , the set of overridings of Inform Operator becomes well formed. p DISCUSSION Our basic rule model, though formal, is similar to the informal model described for the SAMOS system in (Gatziu, et al. 1991, Geppert, et al. 1995) In SAMOS events, conditions and actions can be defined independently of rules. Both class specific and class spanning rules are supported and are inherited by the subclasses. As mentioned earlier, the semantics of inheritance for class spanning rules and rule overriding ....

Gatziu, S., Geppert, A. & Dittrich, K. (1991). Integrating Active Concepts into an Object-Oriented Database System. Proc. of 3rd International Workshop on Database Programming Languages, 399-415.

....involved in coupling the event mechanism. Conclusions and future research plans are given in section 5. 2. Background of Research 2. 1 Related Work on Active Object Oriented Databases There are a number of recent works on active object oriented databases including: Sentinel [CKA 94] SAMOS[GGD92] NAOS[CCS94] REACH[BBK 93, BZB 95] and Ode[GJ91] However, there are a number of differences between their rule systems with ours: 1. Differences in condition predicates. All of the systems allow methods to be called allowing wide variety of operations to be executed during condition ....

S. Gatziu, A. Geppert, and K.R. Dittrich. "Integrating Active Concepts into an Object-Oriented Database System". Proc. 3rd International Workshop on Database Programming Languages, pp.399--415, 1992.

....of a specific number of cancer cases or defining new regions or intervals for clustering. These enhancements concern especially the language necessary for describing active behaviour as well as the implementation of the corresponding runtime system. Active databases (ref. e.g. 3] 4] 5] 6] [7], 9] 14] 15] provide means for specifying active behaviour and monitoring incoming events. They supply rule based languages, as e.g. introduced in [5] Each rule consists of three parts, describing events, conditions and actions (ECA rule for short) The semantics is as follows: each time an ....

S. Gatziu, A. Geppert, K.R. Dittrich: "Integrating Active Concepts into an ObjectOriented Database System", Proc. 3rd. Int. Workshop on Database Programming Languages (DBPL), Nafplion, 1991.

....point(E) 2DAYS) monitors the occurrence of E during two days in August after its first occurrence. 3 Integrating active Components into an OO Environment The combination of active and object oriented characteristics within one, coherent system is another major goal of SAMOS [GGD 91] Using ooDBS characteristics like user defined types, methods, inheritance or encapsulation increases the flexibility of an active mechanism twofold: first in that method and value events are supported and second in that rules are subject to encapsulation and inheritance and are represented as ....

S. Gatziu, A. Geppert, K.R. Dittrich. Integrating Active Concepts into an Object-Oriented Database System. Proc. of the 3. Intl. Workshop on Database Programming Languages, August 91.

....is concerned with the nature of events, conditions and actions and their relationships to the data model. Rule execution refers to the processing of rules, which has to be carried out in the context of the general transaction model supported by the database system (some aspects are presented in [7]) Rule management incorporates tasks for the internal representation of rules and events, for the event detection and the selection of all rules that have to be executed. A short general description of SAMOS can be found in [8] In this paper, we focus on rule specification and rule management. ....

....object oriented environment. In our approach, it is also important that the user is not required to know the internal representation and the handling of events. Our current research focuses on the refinement of the event detector for time events and on socalled value events (as introduced in [7]) Our future research concerns the investigation of the strengths and possible problems of the rule language in concrete applications environments, e.g. in stock applications. In the longer term we plan to provide (design) tools for active database systems. In detail a graphic editor, a debugger ....

Gatziu S, Geppert A, Dittrich K.R. Integrating Active Concepts into an Object-Oriented Database System. Proc. of the 3. Intl. Workshop on Database Programming Languages, Nafplion, August 91

No context found.

S.Gatzin, A.Geppert and K.R.Dittrich, "Integrating Active Concepts into an Object-Oriented Database System", Proc 3rd International Workshop on database programming languages, Nafplion, 1991.

No context found.

GGD91 S. Gatziu, A. Geppert, K.R. Dittrich: "Integrating Active Concepts into an Object-Oriented Database System", Proc. 3rd. Int. Workshop on Database Programming Languages (DBPL), Nafplion, 1991.

No context found.

S. Gatziu, A. Geppert, and K.R. Dittrich, "Integrating Active Concepts into an Object-Oriented Database System", Proc. of the Third International Workshop on Database Programming Languages, August 1991.

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