G. Kappel, S. Rausch-Schott, W. Retschitzegger, and S. Vieweg. TriGS making a passive object-oriented database system active. JOOP, 1994.  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 ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, and S. Vieweg. TriGS making a passive object-oriented database system active. JOOP, 1994.

....etc. Active database research has initially focussed on the integration of active behavior into relational DBMSs (Starburst [74] Ariel [48] POSTGRES [65] A second generation of projects (including Ode [38] Sentinel [17] and SAMOS, later followed by REACH [6, 7] ACOOD [4] NAOS [22] TriGS [50], Chimera [15] and [51] investigated object oriented ADBMS. Reactive behavior as offered by ADBMS can be beneficially used by numerous application areas, such as financial applications [20] network management [3] workflow management [42] medical applications [5] integrity constraints [12, ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Viewweg. TriGS: Making a Passive Object -Oriented Database System Active. Journal of Object-Oriented Programming 7:4, July 1994.

....be subject of future work to consider such a mapping more thoroughly. Currently, there is no accepted standard in the field of active object oriented database systems. Therefore, we decide to show how Situation Activation diagrams can be mapped to an existing system. The selected system is TriGS ([12, 21]) an active extension to the commercial object oriented database system GemStone (GemStone Systems, Inc. We have selected TriGS since GemStone is an interpreting system that provides a flexible framework for an intended prototypical implementation. Since the knowledge model and the execution ....

....prototypical implementation. Since the knowledge model and the execution model of TriGS are comparable with those of other active object oriented database systems, we expect that the lessons learned from mapping to TriGS can be transferred to other systems. For details on TriGS we refer to [12, 21]. When the mapping of active behavior into TriGS is discussed, the term rule is ambiguous. Rule may mean either a rule that is modeled with Situation Activation diagrams or a rule that is defined as part of a TriGS schema. To avoid confusion, we refer to a rule in the former sense as an SAD rule, ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger and S. Vieweg, "TriGS: Making a Passive Object-Oriented Database System Active," in JOOP , 7(4), 1994.

....that must be executed within transactions to assure database consistency and integrity. In the same way rules are executed within a transaction in order to process database operations. Many active database systems models or prototypes have been proposed [Da86, DBB 88, Han89, BBKZ92, CAM93, KRRV94, CFPT95, WC96, MFLS96, Pat] Database products and standard proposals (SQL 92, SQL3) include similar mechanisms. They share a common idea of providing the active functionality to databases but many design differences are found. Active systems may differ on active rule languages and data model ....

Kappel (G.), Rausch-Schott (S.), Retschitzegger (W.) et Vieweg (S.). -- TriGS Making a Passive Object-Oriented Database System Active. JOOP, 1994.

.... applications have been investigated ( CW90, CW91, BCMP94, CS94, CW94, CFPT94, WC96] As a consequence to these various uses of active rules, many active database systems models or prototypes have been proposed ( Da86, SHH87, DBB 88, AG89, Han89, WF90, BM91, DPG91, BBKZ92, SKM92, CAM93, CCS94, KRRV94, CFPT95a] Database products ( Ing92, Ora92, Syb92] and standards ( MM95] proposals include similar mechanisms. Active rule languages and integration of rules in various data models (relational, NF2, object oriented) have motivated numerous works. Events represent a research domain in ....

....a formal description of this model. 1 A RDL [SKM92] Ariel [Han89] Beeri Milo [BM91] Chimera [CFPT95a] EXACT [DPG91] HiPAC [DBB 88] Informix, NAOS [CCS94, Col98] Ode [AG89] Oracle [Ora92] Postgres [SHH87] REACH [BBKZ92] SAMOS [Da86] Sentinel [CAM93] Starburst [WF90] TriGS [KRRV94] 2.2 The FL ARE Model FL ARE is not yet another rule execution model but might be considered as a proposal of standard for active rule execution models. To define this model we turned the dimensions of our taxonomy into constants and parameters. Parameters can take values only within a set of ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, and S. Vieweg, TriGS Making a Passive Object-Oriented Database System Active, JOOP (1994).

....et des donn ees d eriv ees, des autorisations, des alerteurs, des bases de connaissance, des applications de workflow . Les bases de donn ees actives ont donn e lieu a de nombreuses recherches durant les derni eres ann ees [WC96] Elles ont abouti a l impl ementation de plusieurs prototypes [WC96, CC94, SKdM92, KRSWV94, AMC93, GJ91, GD92] tant dans le cadre des bases de donn ees relationnelles que dans celui des bases de donn ees objet. Actuellement, cette technologie a atteint un stade de maturit e tel que plusieurs syst emes de bases de donn ees relationnelles commercialis es offrent des m ecanismes d ex ecution de r egles ....

....ordonn e selon une priorit e statique entre les modules. 2.3 Les syst emes actifs captur es Le tableau de la figure 1 donne quelques exemples des choix s emantiques adopt es par les diff erents syst emes actifs et support es par notre mod ele. Les syst emes consid er es sont : NAOS [CC94] TriGS [KRSWV94], Sentinel [AMC93] A RDL [SKdM92] Starbust [WCL91] Ode [GJ91, GJS92] Chimera, Ariel, WC96] Exact [DPG91] et Samos [GD92] 3 L architecture 3.1 Fonctionnalit es Notre syst eme fonctionne au dessus de la base de donn ees objet passive O2. Ses principales caract eristiques sont les suivantes ....

G. Kappel, S. Rausch-Scott, W.Retschitzegger, S. Vieweg. TriGs : Making a passive object-oriented database system active. Journal of Object-Oriented Programming, July 1994.

....transactions, they are still limited in their support for truly cooperative activities. During the past decade, traditional groupware applications, such as process oriented workflow systems have been extended with transactional abilities. Examples of these are the TriGS flow workflow system [8], which is based on an active database system using a multi parent nested transaction model, and the Exotica system [1] which shows how advanced transaction models, such as Linear Sagas and Flexible Transactions, can be implemented on top of existing workflow systems such as FlowMark. There are ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, and S. Vieweg. TriGS: Making a passive object-oriented database system active. Journal on Object-Oriented Programming, (4), July 1994.

....IN CURRENT ACTIVE OODBS Rule inheritance is provided by most active OODBs, although the exact mechanism for rule inheritance, and in particular rule overriding, is not widely discussed. To the best of our knowledge there has been no work on signature compatibility in active OODBs, and TriGS [Kappel 94] and NAOS [Collet 94] are the only active OODB systems that discuss rule overriding. In TriGS class specific rules (local triggers in TriGS terminology) can be overridden. However, based on the underlying dynamically typed object model, the rule specialization is not required to be signature ....

G. Kappel, et. al., "TriGS - Making a Passive Object-Oriented Database System Active", Journal of Object-Oriented Programming, July-August 1994, 40-63.

.... 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 systems, especially the ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, and S. Vieweg. TriGS making a Passive Object-Oriented Database System Active. JOOP - To be published, 1994.

....different directions ranging from a dynamic evolution of existing coordination policies to proper reactions to unpredictable situations. Active object oriented database systems along with their basic mechanism of ECA rules seem to be a promising technology in order to cope with these requirements [Kappel et al. 1994] . ECA rules allow for an event driven realization of context dependent and time dependent behavior by monitoring a situation represented by an event together with a condition and executing the corresponding action when the event occurs and the condition is true. By encapsulating coordination ....

Kappel, G., Rausch-Schott, S., Retschitzegger, W. and Vieweg, S. 1994. TriGS - Making a Passive Object-Oriented Database System Active. Journal of Object-Oriented Programming (JOOP), 7(4), 40-51.

....on the architecture and implementation of TriGS Debugger can be found in the section following. The paper concludes with some lessons learned from user experiences and points to future research. 2 Overview of TriGS TriGS Debugger is realized on top of TriGS (Triggersystem for GemStone) [Kapp94a], Kapp98b] representing an active extension of the object oriented database system GemStone [GemS00] The two main components of TriGS are TriGS Engine comprising the basic concepts employed in TriGS for specifying and executing active behavior and TriGS Developer, an environment supporting the ....

....event selectors and or rules. For example, the message event selector post(Machine, changeState: is used as component event selector of MaintenanceRule 1, as Esel C Esel A of ScheduleRule 1 and as Esel C of ScheduleRule 2. Due to inheritance, rules are inherited along the class hierarchy [Kapp94a]. However, to reduce complexity, edges from the subclasses of the class containing the respective method to the event selector(s) are not visualized, except the method has been overridden in a 5 subclass. For example, the event selector post(Machine, changeState: is associated with ....

Kappel, G., Rausch-Schott, S., Retschitzegger, W., Vieweg, S., TriGS - Making a Passive Object-Oriented Database System Active, Journal of Object-Oriented Programming (JOOP), 7(4), 1994, pp. 40-63.

....research during the last years. Research on active databases has been driven by a need for supporting (re )active database functionality important for a number of non traditional applications such as computer integrated manufacturing (CIM) and workflow management [Atti93] Daya90] Garc91] [Kapp94a], Kapp95] Active database capabilities are now finding their way into many of the most popular commercial database management systems. Conventional database management systems are passive, i.e. they only perform operations in response to commands issued by users or applications. In contrast, ....

.... actions when the event occurs and the conditions evaluate to true [Beer91] There exists quite a number of different prototype approaches aiming at the integration of active concepts with object oriented database systems (e.g. Buch95] Chak94] Coll94] Gal95] Gatz95] Geha96] [Kapp94a], Mede91] Comparing to commercial database systems with active capabilities [Orac92] both knowledge model and execution model of these prototype systems are more advanced. Concerning the knowledge model, e.g. different kinds of events such as time events, external events and composite events ....

[Article contains additional citation context not shown here]

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Vieweg, TriGS - Making a Passive Object-Oriented Database System Active, Journal of Object-Oriented Programming (JOOP), July-August, 1994

....of the DBS considered in a CIM environment. Active database management systems (ADBMS) are designed to support the definition of consistency constraints in terms of production rules tightly coupled to the entities in the database. A production rule may be specified as event condition action rule [Dayal88, Kappel93] where the event specifies an operation performed within the database, the condition part describes some additional constraint, and the action part specifies operations on the database. ADBMSs also provide active monitoring of the production rules. If an event takes place it triggers the ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Vieweg; TriGS - Making a Passive Object-Oriented Database System Active; accepted for publication in: Journal of Object-Oriented Programming (JOOP); 1993

.... inheritance in TriGS was, that the underlying object oriented model of GemStone, which is Smalltalk, adheres to this kind of inheritance, and, in our opinion, the kind of inheritance used for rules should not contradict the kind of inheritance supported by the underlying object oriented model [Kapp94], Rets97] However, what should be investigated in the future is, how far other kinds of inheritance such as specification inheritance and specialization inheritance [Wegn88] are useful for being applied to rules. ....

Kappel, G., Rausch-Schott, S., Retschitzegger, W., Vieweg, S., TriGS - Making a Passive ObjectOriented Database System Active, Journal of Object-Oriented Programming (JOOP), 7(4), 1994.

....attempts exist to integrate active concepts into object oriented databases. Current approaches to active object oriented database systems, however, do not consider the various active concepts together with some of the basic object oriented concepts. The system TriGS ( Trigger system for GemStone) [Kapp93, Kapp94] focuses on several concepts that originate both from shortcomings of existing active object oriented systems and from advanced requirements of CIM applications. TriGS makes explicit use of objects, message passing, inheritance, and overriding to provide a seamless integration between rules and an ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Vieweg, TriGS - Making a Passive Object-Oriented Database System Active, to be published in: Journal of Object-Oriented Programming (JOOP), 1993

....rules) These rules allow the designer to monitor situations represented by events together with conditions and execute the corresponding actions when the events occur and the conditions are true. ECA rules may be stored as first class objects in so called active object oriented database systems [Kappel et al. 1994]. The second problem concerns reusability. Application designers have to decide on the implementation of a particular business policy over and over again for each application domain since appropriate abstraction mechanisms are not available. This problem can be captured by introducing a framework ....

KAPPEL, G., RAUSCH-SCHOTT S., RETSCHITZEGGER, W. AND VIEWEG, S. 1994. TriGS - Making a Passive Object -Oriented Database System Active. Journal of Object-Oriented Programming (JOOP), 7(4), 40-63.

....different directions ranging from a dynamic evolution of existing coordination policies to proper reactions to unpredictable situations. Active object oriented database systems along with their basic mechanism of ECA rules seem to be a promising technology in order to cope with these requirements [Kappel et al. 1994]. ECA rules allow for an event driven realization of context and time dependent behavior by monitoring a situation represented by an event together with a condition and executing the corresponding action when the event occurs and the condition is true. By encapsulating coordination policies within ....

KAPPEL, G., RAUSCH-SCHOTT S., RETSCHITZEGGER, W. AND VIEWEG, S. 1994. TriGS - Making a Passive Object-Oriented Database System Active. Journal of Object-Oriented Programming (JOOP), 7(4).

....systems as well. The rest of the paper provides a detailed account of the execution model and implementation aspects of TriGS. To make the paper self contained the underlying knowledge model is shortly summarized in the next section. For an in depth discussion of the knowledge model we refer to [Kapp94a]. A comparison with related approaches and an outlook on further work concludes the paper. The work on TriGS is part of the EC ESPRIT project Design, Development and Implementation of a KnowledgeBased Leitstand (KBL No. 5161) 1 aiming at the development of next generation production scheduling ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Vieweg, TriGS - Making a Passive Object-Oriented Database System Active, to be published in: Journal of Object-Oriented Programming (JOOP), 1994

.... with the individual needs of organizations and, on the other hand, has to dynamically react to frequently changing requirements or unpredictable situations [10] A powerful means to meet these requirements for flexibility of coordination policies are active objectoriented database systems (AOODBS) [7, 18]. The realization of coordination policies by means of Event Condition Action (ECA) rules, which represent the most prominent basic mechanism of such active systems, leads to various advantages. To start with, ECA rules enable the system to monitor certain situations and to react to them ....

....time. In TriGS f low , roles are used to specify capabilities and duties of agents, consequently supporting the assignment of activities to agents. For details of the role model of TriGS f low we refer to [20] The active component of TriGS f low is based on TriGS ( Trigger System for GemStone) [18]. TriGS has been implemented on top of GemStone and makes explicit use of objects, message passing, inheritance, and overriding to provide a seamless integration between rules and the object oriented data model of GemStone. TriGS rules consisting of events, conditions, and actions monitor the ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger and S. Vieweg, "TriGS: Making a Passive ObjectOriented Database System Active", in Journal of Object-Oriented Programming (JOOP), vol. 7(4), July/August 1994.

....and the rule based paradigm. The transaction paradigm and the distribution paradigm are not subject of this paper. A first prototype of the workflow model has been implemented on top of TriGS, an active extension of the commercially available object oriented database system GemStone TM [Kapp94, Butt91]. 2. Overview of TriGS TriGS makes explicit use of objects, message passing, inheritance, and overriding to provide a seamless integration between rules and an object oriented data model. Rules consisting of events, conditions, and actions monitor the behavior of objects and can be attached to ....

....different kinds of rules are orthogonal to each other. In the following we discuss the use of ECA rules for TriGS flow in detail. If not stated otherwise, the coupling modes between event and condition as well as between condition and action are assumed to be immediate according to the notion in [Kapp94]. Figure 2: Application areas for ECA rules 3.2.1 Activity Ordering The relationships between activities, i.e. the activity net can be realized by using ECA rules, thus specifiying a certain workflow type. Each relationship between two activities is mapped to a single rule. The event always ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Vieweg. TriGS - Making a Passive Object-Oriented Database System Active, Journal of Object-Oriented Programming (JOOP), July-August, 1994

....The transaction paradigm and the distribution paradigm are not dealt with in this paper but are subject of ongoing research. A first prototype of the workflow model has been implemented on top of TriGS, an active extension of the commercially available object oriented database system GemStone [Kapp94a, Butt91]. The paper is organized as follows: Section 2 introduces the object oriented workflow model as well as integration aspects. Section 3 incorporates rule modeling and Section 4 points to ongoing research. 2. Object oriented workflow model In the following we describe our workflow model which is ....

....of those systems and provide the necessary transformation to and from those systems. Real interoperability between TriGS flow and other (legacy) systems, e.g. in terms of multiworkflow models, is subject to ongoing research. 3. Rule model of TriGS flow 3. 1 Basic concepts of TriGS TriGS [Kapp94a, Kapp94b] is an active extension to activity 1 activity 2 activity 3 .m1 .m2 .m3 .m4 Class B .m5 activity 4 Internal Application External Application WFMS Class A Class C ooDBS the commercial object oriented database system GemStone and has been developed as part of a larger EC ESPRIT project ....

[Article contains additional citation context not shown here]

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Vieweg, TriGS - Making a Passive ObjectOriented Database System Active, Journal of Object-Oriented Programming (JOOP), JulyAugust, 1994

....a specific design situation recurs and thus is worth to be specified by a corresponding rule pattern, existing rules can be used for this abstraction process (cf. in Figure 1) 3. The Underlying Model We define rule patterns on the basis of an AOODBS called TriGS ( Trigger system for GemStone) [Kapp94a]. Like most active systems, TriGS is designed according to the ECA paradigm [Daya88] Rules and its components are implemented as first class objects allowing both the definition and modification of rules during run time. Figure 2 shows the basic structure for specifying rules in TriGS using the ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Vieweg, TriGS - Making a Passive Object-Oriented Database System Active, Journal of Object-Oriented Programming (JOOP), July-August, 1994

....semantic modeling can significantly help to tackle the rule method problem. 1 Introduction Active object oriented databases represent the structure of real world entities by attributes, their passive behavior by methods, and their active behavior by eventcondition action rules (ECA rules) [8, 7, 12, 18, 1, 5]. An ECA rule defines what action is to be taken, if the specified event occurs and the specified condition holds. e.g. when an item is to be deleted (the event) and orders for that item exist (the condition) then abort the transaction (the action) Events of ECA rules can be basic or ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, and S. Vieweg. TriGS: Making a Passive Object-Oriented Database System Active. Journal of Object-Oriented Programming, 7(4):40--51, 1994.

....car may be reserved at a very special rate for one week. This policy can be best expressed by a rule which is triggered by a composite event as follows (note, we use a simplified notation borrowed from our underlying active object oriented database system called TriGS, Triggersystem for GemStone [14, 15]) DEFINE RULE reserveRentalCar AS ON e1: PRE(Hotel, reserve:roomRequest for:interval customer:aCust) AND e2: PRE(Airline, book:destination for:interval customer:aCust) DO IF checkCustomer regular customer accepts cheap rental car offer THEN EXECUTE rentalOffice reserve:compact ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger and S. Vieweg, "TriGS: Making a Passive Object-Oriented Database System Active," in Journal of Object-Oriented Programming (JOOP), vol. 7, pp. 40-51, July/August 1994.

....to a fully fledged running example situated within the area of workflow systems is available as technical report [Kapp95d (http: www.ifs.uni linz.ac.at ifs publications.html) 2. The Underlying Model We define rule patterns on the basis of an AOODBS called TriGS ( Trigger system for GemStone) [Kapp94a]. Like most active systems, TriGS is designed according to the ECA paradigm [Daya88] Rules and its components are implemented as first class objects allowing both the definition and modification of rules during run time. Figure 1 shows the basic structure for specifying rules in TriGS using the ....

G. Kappel, S. Rausch-Schott, W. Retschitzegger, S. Vieweg, TriGS - Making a Passive Object-Oriented Database System Active, Journal of Object-Oriented Programming (JOOP), July-August, 1994

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