Buchmann, A.P, Zimmermann, J., Blakeley, J.A., Wells, D.L. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. Proc. IEEE Int'l. Conference on Data Engineering, Taipei, Taiwan, 117-128, March 1995.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....are currently provided by most commercial relational database systems. This is in contrast to commercially available object oriented database systems which do not yet support active rules. However, extensive work on active object oriented databases (AOODBMS) has been carried out in recent years [13, 1, 12, 3, 6]. This area of research can be seen as an enabling technology for supporting applications in heterogeneous information systems. Examples of applications in this category are advanced workflow management systems, real time plant control systems, and process centred software development environments ....

A. Buchmann, J. Zimmermann, J. Blakelyand, and D. Wells. Building an integrated active oodbms: Requirements, architecture, and design decisions. In Proc. of IEEE Data Engineering, 1995.

....The modes specify the transaction relationship of 1) database events to condition evaluation and 2) condition evaluation to action execution. This method has been effective in integrating Region II applications [86] However, ongoing research has lead to the development of dozens of coupling modes [21,24,33,98]. As a result, coupling modes often burden application programmers with extremely difficult conceptual specifications, and they have proven to be one of the most difficult conceptual obstacles in the development of hard active database applications. It is the author s belief that the details of ....

....execution of the pair occurs in separate transactions. Table 2 summarizes the semantics of these coupling modes. REACH proposes the additional modes of detached causally dependent in either of parallel, sequential or exclusive modes to give abort and commit semantics for decoupled transactions [21]. 2.2.3 Concurrency Control and Recovery A major difference between active databases and expert systems is that active database programs may contain readers and writers that are external to the rule programs. However, concurrency with respect to execution correctness between the rule application ....

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A. Buchmann, J. Zimmermann, and J. Blakeley, "Building an integrated active OODBMS: Requirements, architecture, and design decisions," in Proceedings of the 11th International Conference on Data Engineering. Taipeh, Taiwan, March, 1995, pp. 117-128.

....evaluation and 2) condition evaluation to action execution. This explicit specification of coupling modes by application programmers promises to increase system throughput by maximizing flexibility. However, the progression of research has lead to a proliferation of the number of coupling modes [6,8,12]. As a result, coupling modes often burden application programmers with extremely difficult conceptual specifications. In this paper, we begin deciphering which coupling modes are necessary to achieve useful active database programming. We have observed that a number of our active database ....

....completion; and in decoupled mode, execution of the pair occurs in separate transactions. Other coupling modes that have been proposed include the detached causally dependent in either of parallel, sequential or exclusive modes to give abort and commit semantics for decoupled transactions [6]. 2.2. Monotonic Log Monitors (MLM) This paper presents the simplifications that can be discerned from a class of applications called monotonic log monitors (MLM) MLMs are a class of real time active database applications [17,24] Such systems process some form of real time data logged to a ....

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A. Buchmann, J. Zimmermann, J. Blakeley, "Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions", Proceedings of the 11th International Conference on Data Engineering. Taipeh, Taiwan, March, 1995.

....Hochschule Darmstadt, Germany. Influenced by HiPAC and DOM, it developed a core system named REACT, which implements a language comparable to Snoop (2.16) Two prototypes use O2 and ObjectStore as a platform in order to implement the object oriented 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] ....

....Environment Supporting active database functionality in a distributed environment poses additional challenges for maintaining and executing rules. References: BOGM92] CW92] Etz93a] Jae95] Ulu95] 3. 8 Architecture Architecture of Active Databases are addressed in: References: BZBW95] Cha92] CZ93] Etz93d] Jas94] 3.9 Implementation Issues There are prototypes implemented, and the following papers discuss details of implementations: References: BZBW95] Car92] CKAK93] CN90] Coh89] DM89] GD93b] GJS92a] Han92b] Han92a] HB91] HK87] HK89] KD93] ....

[Article contains additional citation context not shown here]

A.P. Buchmann, J. Zimmermann, J.A. Blakeley, and D.L. Wells. Building an integrated active oodbms: Requirements, architecture, and design decisions. In Proc. 11th Intl. Conf. on Data Engineering, pages 117--128, Taipei, Taiwan, March

.... the events that make up composite event originate in multiple transactions, no identification of the spawning transactions is possible [116] Rules that are invoked by temporal events (time triggered) can only be run in an independent decoupled mode, since they are not triggered by a transaction [19]. To simplify the creation of the rule base a tool, GRANT, has been developed. This graphical tool prompts the user for necessary information, provides certain default choices, creates C language structures, and maps rules to C functions stored in a shared library [18] The event manager in ....

A. P. Buchmann, J. Zimmermann, J. A. Blakeley, and D. L. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. In Proceedings of the 11th International Conference on Data Engineering, pages 117--128. IEEE Computer Society Press, 1995.

....algorithms for processing rules are more efficient, and programmers cannot circumvent relationships defined in an object model, A second community has approached rules in the context of active object oriented databases. Many active databases (e.g. Sentinel [26] Ode [30, 31] ADAM [32] REACH [33], SAMOS [34] follow an event condition action paradigm [35] where ECA rules associate events with conditions and actions. Ode uses a simpler event action model, with conditions folded into events [36] Events are monitored and trigger rules. Rule conditions are evaluated when rules are ....

A. P. Buchmann, J. Zimmermann, J. A. Blakeley, and D. L. Wells. Building an integrated active oodbms: Requirements, architecture, and design decisions. In Proceedings of the 11th International Conference on Data Engineering, 1995.

....starts, scheduling of multiple rules, 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 ....

....of complex events and offers a small number of event constructors that allow expressive event definitions in combination with the concept of monitoring intervals [26, 32] 5 of 31 . Detection of complex events. In contrast to several other techniques for detection of complex events [7, 18, 39], the event detector of SAMOS is based on Petri Nets. Generally, Petri Nets allow both powerful and succinct descriptions of many complex systems. It turned out that they are suitable for the modeling and the detection of complex event definitions [33] Integration of active and object oriented ....

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A.P. Buchmann, J.Blakeley J.A. Zimmermann, D.L. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. Proc. 11 th Int'l Conf. on Data Engineering, Taipei, Taiwan, March 1995.

....graphs that reflect temporal dependencies. Dayal et al. 5] use rules as they are provided by active database systems to specify the ordering of transactions. They do this by specifying rules that are triggered by transaction events and by exploiting the capabilities of coupling modes (cf. [3]) The basic limitation of these approaches is that all related transactions must be known in advance. Our model is by far more modular and general: A transaction can be pinned to a point in time without the need to consider all the transactions that potentially may be executed around the critical ....

A.P. Buchmann, J. Zimmermann, J.A. Blakeley, and D.L. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. In Proc. of the 11th Intl. Conf. on Data Engineering (ICDE), 1995.

....in a flexible and time dependent way. Examples of activities in the area of active databases are Postgres [SHP88] and Starburst [WF90] Recently, these active mechanisms have been transferred to and integrated into object oriented database systems, see for instance the prototype system REACH [BZBW95] From our point of view it is obvious that mechanisms of active database systems can be used to realize or support prototyping or implementation of object specifications in a rather straightforward way. Above that, an additional motivation for employing ECA rules is based on the observation ....

....In comparison to hardcoded methods, ECA rules seem to be more suitable for modeling dynamic behavior of objects. In fact, ECA rules have the advantage that additional or modified behavior of objects can be easily integrated into the system at runtime (see active databases like REACH [BZBW95] Hence, the reaction on a specific event may be changed dynamically by replacing removing an existing ECA rule or by integrating a new one. Therefore, we are of the opinion that behavior of objects which 5 cannot be completely specified at compilation specification time should be expressed by ....

[Article contains additional citation context not shown here]

A. P. Buchmann, J. Zimmermann, J. A. Blakeley, and D. L. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. In P. S. Yu and A. L. P. Chen, editors, Proc. of the 11th Int. Conf. on Data Engineering (ICDE'95), Taipei, Taiwan, pages 117--128. IEEE Computer Society, March 1995.

....of host language programming, if the rules do not fit well with the object model, a pattern matching approach might be preferable. A second community has approached rules in the context of active object oriented databases. Many active databases (e.g. Sentinel [27] Ode [31, 32] ADAM [33] REACH [34], SAMOS [35] follow an eventcondition action paradigm [36] where ECA rules associate events with conditions and actions. Ode uses a simpler event action model, with conditions folded into events [37] Events are monitored and trigger rules. Rule conditions are evaluated when rules are ....

A. P. Buchmann, J. Zimmermann, J. A. Blakeley, and D. L. Wells, "Building an integrated active oodbms: Requirements, architecture, and design decisions," in Proceedings of the 11th International Conference on Data Engineering, 1995.

.... event and by one or more conditions and to execute the corresponding 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 ....

....for the execution models. This is especially the case for transactional aspects within execution models. Among the most challenging research problems is the development of a transaction model in the presence of so called composite events, i.e. events representing a combination of other events [Buch95], Chak94] We suggest to tackle this research problem by introducing multi parent subtransactions. The model of multi parent subtransactions is based on a simple extension of the nested transaction model [Hrd93] Moss85] It provides a means to naturally map the semantics of composite events ....

[Article contains additional citation context not shown here]

A.P. Buchmann, J. Zimmermann, J.A. Blakeley, D.L. Wells, Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions, Proc. of the 11th Int. Conf. on Data Engineering, Taipeh, 1995

....component, which tightly couples the operating system and the database management system. Further, the architecture assumes that all events are routed through the scheduler, since the response to the event needs to be scheduled like any other task in the system. The REACH project [BBKZ92, BZBW95] is an active object oriented database being built at the Technical University of Darmstadt, Germany. One of the issues addressed in REACH is time constrained rule processing in an active database system. A special type of relative temporal event, milestones, was introduced in REACH [BBKZ94] ....

A.P. Buchmann, J. Zimmermann, J. Blakely, and D. Wells. Building an integrated active oodbms: Requirements, architecture, and design decisions. In Proc. IEEE Data Engineering, 1995.

....time and the database state to recognize predefined situations and to react to them accordingly in order to meet a company s business policy. Modeling such business rules requires concepts that are not yet appropriately provided by current prototypes of active object oriented database systems [2, 4, 6, 18, 19] and recent approaches to active object oriented database design [1, 14, 20, 25] P. Lang and W. Obermair are funded by the Austrian Science Foundation (FWF) under contract P10320MAT. 1 The requirements on a rule language for modeling business rules from an external observation perspective are ....

A. P. Buchmann, J. Zimmermann, J. A. Blakeley and D. L. Wells, "Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions," in Proc. ICDE`95, 1995.

....19 http: www.his.se ida drts techTransfer 1996 deedsFollowup.ps.Z 20 http: www.his.se ida drts techTransfer 1996 deedsFollowuphandout.ps.Z 21 http: www.his.se ida drts techTransfer 1996 deedsInSe.ps.Z 22 http: www.his.se ida drts techTransfer 1996 deedsInSehandout.ps. Z 10 Buchmann et al. 1995] papers covering the REACH project, which is another active real time database project; Chakravarthy and Mishra, 1994, Chakravarthy et al. 1993, Chakravarthy et al. covering the Snoop event detector based on event graphs which is an efficient event monitoring techniqure, and event ....

....Distributed systems. Books: Mullender, 1994] a very good book covering most of the interesting issues in distributed computing. ffl Event monitoring. Articles: Chakravarthy and Mishra, 1994, Chakravarthy et al. 1993, Chakravarthy et al. the snoop event detector; Buchmann, 1994, Buchmann et al. 1995] which gives a good insight in problems concerning monitoring active (real time) databases [Deutsch, 1994] which has a comparison of different event detection algorithms used in active database; Mellin, 1996] a survey giving an overview event monitoring; Haban and Shin, 1989, Haban ....

Buchmann, A. P., Zimmermann, J., Blakeley, J. A., and Wells, D. L. (1995). Building an integrated active OODBMS: Requirements, architecture, and design decisions. Data Engineering.

....type X refers to a certain expression of constituent event types except X, as recursion is not allowed and operators. A composite event instance x is a typed representation for a combination of constituent event instances. Languages for event compositions provide a variety of operators ( BZBW95] PW93] WC94] Without discussing those languages, we classify event operators into three groups: constructors combine events from different sources to form new result tuples. collectors collect events from different sources and merge them without constructing a new event tuple. ....

A.P. Buchmann, J. Zimmermann, J.A. Blakeley, and D.L. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. In Proc. 11th Intl. Conf. on Data Engineering, Taipei, Taiwan, March 1995. IEEE, IEEE Computer Society Press.

....associated with BODs; not only those specified by OAG but also those defined by application systems are supported. The concept and use of ECAA rules for constraint specification and enforcement is adapted from some existing active database management systems [ACT96, HAN93] such as HiPAC [DAY88, BUC95], Ariel [HAN92] Alert [SCH91] Sentinel [CHA94a] POSTGRESS [STO91] ODE [GEH91, GEH96] Starburst [LOH91, WID90] and our own work on OSAM .KBMS [SU91, SU92, SU93, SU95, SU96a, SU96b, SHY96] In active systems, database operations or user defined operations can be treated as events, which can ....

Buchmann, A.P., Zimmermann, J., Blakeley, J.A., and Wells, D.L., "Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions", Proceedings of IEEE International Conference on Data Engineering, Taipei, Taiwan, 1995, pp. 117-128.

....constraints in federated database systems is required respecting as much as possible the autonomy of the local database systems. The approach we describe in this paper is based on mechanisms as they are used for integrity enforcement in active database systems (e.g. SAMOS [GD94b] REACH [BZBW95] Sentinel [CKTB95] From our point of view, active rules (ECA rules) are a promising principle not only for integrity enforcement in single, centralized database systems, but also for federated heterogeneous systems. This is due to the fact that the active rule paradigm is in principle ....

....provides active functionality on top of the object oriented database system ObjectStore. In contrast, in the built in approach all active capabilities are integrated into the kernel of a database system. This approach is used, for example, by the prototype systems Sentinel [CKTB95] and REACH [BZBW95] which integrate active mechanisms into the object oriented database system OpenOODB. So far, we have presented the essential notions and issues of active database systems needed to understand how active mechanisms can be used in a federated database environment for integrity constraint ....

[Article contains additional citation context not shown here]

A. P. Buchmann, J. Zimmermann, J. A. Blakeley, and D. L. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. In P. S. Yu and A. L. P. Chen, editors, Proc. of the 11th IEEE Int. Conf. on Data Engineering (ICDE'95), Taipei, Taiwan, pages 117--128. IEEE Computer Society Press, March 1995.

....however is the definition of composite events which was followed by TriGS. It has to be mentioned that it was not the main goal of TriGS to establish yet another composite event definition language. Rather, the approach is based on the work of existing active systems, such as Ode [Lieu96] REACH [Buch95], Samos [Gatz95] and Snoop [Chak95] Furthermore, The application of TriGS to a non standard application area as mentioned above made it necessary, to put special emphasize on the following design and implementation goals: Powerful Representation of Composite Events. The representation of ....

....which represent the composite event selector that the primitive event selector is part of. 3.2 Life Span and Consumption of Events Life Span of Events. The life span of partially composed events in TriGS is, in principle, neither restricted to a single transaction as it is the case in REACH [Buch95] and Snoop [Chak94] nor to an application like in SAMOS [Gatz95] Rather, a partially composed event stays alive as long as it is not explicitly scavenged by means of a special method provided by TriGS. If the life span would only be for a transaction, then composite events spanning several ....

[Article contains additional citation context not shown here]

Buchmann, A.P., Zimmermann, J., Blakeley, J.A., Wells, D.L., Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions, in P. S. Yu, A. L. P. Chen (eds.), Proceedings of the 11th International Conference on Data Engineering (ICDE '95), IEEE Computer Society Press, Taipeh, Taiwan, 1995.

....actions in the form of Event Condition Action #ECA# rules #Dayal et al. 1988a#. ADBMSs have received great attention lately, and several prototypes of object oriented ADBMSs are already available #e.g. ACOOD #Berndtsson, 1991#, NAOS #Collet et al., 1994#, Ode #Agrawal and Gehani, 1989#, REACH #Buchmann et al. 1995#, SAMOS #Gatziu et al. 1994#, SENTINEL #Chakravarthy et al. 1994##. We are currently in a position to evaluate the performance of ADBMSs by concentrating on # the performance requirements of di#erent architectural approaches; i.e. integrated versus layered, # di#erent techniques used for ....

....of primitive and composite events, # rule #ring, # event parameter passing, # treatment of semi composed events, and # rule administration tasks. The OBJECTIVE Benchmark comprises a number of operations that evaluate the issues stated above, and those operations were #rst run on REACH #Buchmann et al. 1995#. REACH is a full #edged operational object oriented ADBMS which is tightly integrated in Texas Instruments Open OODB #Wells et al. 1992#. The results reported in this paper reveal that REACH combines advanced features of current ADBMS proposals from the functionality point of view. As for its ....

[Article contains additional citation context not shown here]

Buchmann A. P., Zimmermann J., Blakeley J., and Wells D. L., Building an integrated active OODBMS: requirements, architecture and design decisions, in Proc. of the 1995 Data Engineering Conference,Taipeh, 1995.

....programmers. This chapter gives a brief overview of the REACH system implemented on OpenOODB. Currently, efforts are underway to port the REACH functionality to ObjectStore. 14.1 Introduction The REACH project set out to build an active OODBMS with full active functionality [BBKZ93, BBKZ92, BZBW95] This was considered important since previous projects had set ambitious goals and specified a broad range of functionality [DBB 88] but no robust system with full active functionality that could be used for actual implementation of applications was available. The initial goal was to use a ....

A.P. Buchmann, J. Zimmermann, J. Blakeley, and D. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. In Proc. 11th Intl. Conference on Data Engineering, Taipei, Taiwan, March 1995.

....basic mechanisms for composite event specification. Compose [18] introduced powerful event operators. Snoop [8] introduced a formal definition of primitive and composite events based on a global history log, and four event consumption policies: recent, chronicle, continuous and cumulative. Reach [6] provided mechanisms for efficient detection and composition based on the SAMOS [16] algebra. Ode [22] proposed complex event composition but used timestamps for event identification and required a total ordering. Recent efforts have concentrated on unbundling database functionality to provide, ....

A. Buchmann and J. Zimmermann and J. Blakeley and D. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. In Proceedings of ICDE '95, pp. 117-128, March 1995.

....of other properties of an object. Expressed differently, we want to be able to detect a primitive event, such as a method event, independently of an object being persistent or transient, being a system object or a user defined object. This property is known as orthogonality of monitoring and type [BZBW95]. Among the mechanisms that have been proposed for method event detection, the most popular is method wrapping. Method wrapping consists in bracketing a method with a begin method and an end method signal. Depending on whether a rule exists that subscribes to this method event (either before or ....

....for which rules are known to exist. Wrapping every method improves flexibility since a new rule that consumes a given method event that has no previous subscription can be added without having to wrap the corresponding method and recompiling the object class definition. This approach was taken in [BZBW95, BDZH95]. However, this flexibility comes at a price. If every method is wrapped independently of whether a rule subscribes to that event or not, some overhead is paid before and after the execution of each rule to check if a subscription exists. Hand wrapping a method that should be monitored was used 38 ....

[Article contains additional citation context not shown here]

A.P. Buchmann, J.Zimmermann, J.Blakeley, and D.Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. In Proc. 11th Intl. Conference on Data Engineering, Taipei, Taiwan, March 1995. 2. Architecture of Active Database Systems 47

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Buchmann, A.P, Zimmermann, J., Blakeley, J.A., Wells, D.L. Building an Integrated Active OODBMS: Requirements, Architecture, and Design Decisions. Proc. IEEE Int'l. Conference on Data Engineering, Taipei, Taiwan, 117-128, March 1995.

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A. Buchmann, J. Zimmermann, J. Blakely, and D. Wells. Building an integrated active oodbms: Requirements, architecture, and design decisions. In Proc. of IEEE Data Engineering (to appear), 1995.

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A. P. Buchmann, J. Zimmermann, J. A. Blakeley, and D. L. Wells. Building an Integrated Active OODBMS: Requirements, Architecture, and Design, and Design Decisions. In Proceedings of the Eleventh International Conference on Data Engineering, pages 117-128, 1995. 22

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