Narain H. Gehani, H. V. Jagadish, and Oded Shmueli. Composite event specification in active databases: Model & implementation. In Li-Yan Yuan, editor, Proceedings of the Intl Conference on Very Lage Data Bases (VLDB), pages 327--338, Vancouver, Canada, August 1992. Morgan Kaufmann.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....is more declarative, while ADeLe s approach is more procedural. The syntax for ADeLe is a hybrid of XML and C. ADeLe is designed mainly for detection at a local level using network traffic. SEL is an event correlation language used in the SHAMAN network management scripting Framework [73] ODE [16] and CEDAR [22] are languages designed for specifying active database triggers. EBBM [4] is designed to create meaningful abstractions from system events for debugging purposes. These languages are designed with precise expressivity as their main criterion and are generally not scalable. 8.3 ....

N. Gehani, H.V. Jagadish, and O. Shumeli. Composite Event Specification in Active Databases: Model and Implementation. In Proc. 18th Interna-tional Conference on Very Large Data Bases, 1992.

....E 1 ,E 2 , The fact that an event e i is an instance of an event class E j is denoted membership, i.e. e i E j . Definition 4 (Composite Event) Composite event instances are formed by temporal combinations of event instances. Note that our notion of composite events differs from Gehani [8], where a composite event is a set of the events it is formed of. The definition of composite events requires temporal operators and additional parameters for the handling of duplicate events, for details see [13] Composite event operators are, e.g. sequence (E 1 ; E 2 ) t , conjunction ( E 1 ....

....of composite events Automata Composite event expressions are similar to regular expressions if they are not parameterized. Using this observation, it is possible to implement event expressions using finite automata. The first approach for using automata has been made in the Compose system of Ode [8], an active database system. The history of events provides the sequence of input symbols to the automaton implementing the event expression. The automaton input are the primitive event components from the corresponding composite event as they occur in the history. If the automaton enters an ....

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model & implementation. In Proceedings of the 18th International Conference on Very Large Data Bases, 1992.

....A TOPSS) Event centered systems use Boolean combinations of predicates on attribute values. Additionally, several of these systems carry the notion of composite events that are temporal combinations of events, such as a sequence. Composite events have been extensively studied in active databases [11, 16, 36]. Only few sophisticated profile definition languages using 4 composite events have been implemented [19, 14] A combination of concepts from active databases and event notification systems are Event Action Systems (EAS) In such systems (e.g. in Yeast [17] the user profile defines an action ....

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model & implementation. In Proceedings of the Intl. Conference on Very Large Data Bases (VLDB), 1992. 19

.... rules [9] Sophisticated research prototypes have in fact been imple mented recently to provide [his capability an incomplete list of such systems includes [9, 13, 10, 4] These systems feature composite event detection mechanisms, which are based on formalisms such as Finite State Automata [12]. Petri Nets [11] or Event Graphs [3] The problem of formally specifying the semantics of active rules remains largely unsolved. Indeed, giving a formal semantics to active database behavior presents a challenge even when only simple events are involved. For composite event expressions, this ....

....all events El, Er occur simultaneously. El, E, E) A disjunction of events. It occurs when at least one event among E1, En occurs. E : It occurs when not any instance of E occurs. A basic number of additional (derived) constructs may be defined in terms of the ones (see also [12]) Some of these are: any The disjunction of all basic events (of the types monitored) It occurs every lime such an event occurs. E,E2, E, El, any, E, any, any, E, Relaxed sequence. It consists of an instance of El, followed later by an instance of E2, followed ....

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N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specifi- cation in active databases: Model and implementation. In Proceedings of the 18th VLDB International Conference, pages 327-338, 1992.

....databases, temporal or deductive databases, temporal data mining, time series analysis, and distributed systems. In the area of active database systems, the problem of event rule specification has been evaluated for several years (see, e.g. 8] also with special focus on composite events [15, 16, 19, 14, 31, 30] and temporal conditions (e.g. 14, 11, 12] Active database systems can rely on the transactional context for the composition of events. Trigger conditions can be defined based on the old and new state of the database, thus using the concept of states rather than describing the event itself. ....

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model & implementation. In L.-Y. Yuan, editor, 18th International Conference on Very Large Data Bases, August 23-27, 1992.

....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 of different events. In active databases, events correspond to situations that ....

....causeeffect relationships. One important issue when dealing with events is to provide an expressive event specification language with a clear semantics and an eiticient detection mechanism. Proposals have been made for event specification language and event detection in active database systems [5, 4, 14, 18, 26, 25]. However they do not consider deeply enough the fact of composing events that are themselves composite events and they do not really explain what are negative events, i.e. events using negation operator, and how to deal with such events during the detection process. Ode [26] uses an extended ....

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O. Shmueli N.H. Gehani, H.V. Jagadish. Composite Event Specification in Active Databases: Model 85 Implementation. In Proc. of the 18th Int. Conf. on Very Large Data Bases, September 1992.

....M 2 means that any given sequence will occur at exactly the same situations under both M 1 and M 2 . This ultimately leads to the same active behavior under both M 1 and M 2 . 5 Related Work The problem of specifying complex events in active databases has been recognized not to be trivial( 3] [5], 4] 15] Proposals for solving it can be classified in three groups. The first group uses regular expressions and context free grammars to specify complex events (see, e.g. 5] The second group uses graph based methods to specify them ( 3] 4] Finally, the third group uses a logic based ....

....Work The problem of specifying complex events in active databases has been recognized not to be trivial( 3] 5] 4] 15] Proposals for solving it can be classified in three groups. The first group uses regular expressions and context free grammars to specify complex events (see, e.g. [5]) The second group uses graph based methods to specify them ( 3] 4] Finally, the third group uses a logic based approach (for good examples of this approach, see [5] 15] Very often, these approaches are expressible in form of an event algebra ( 16] Using a metamodel for event algebras, ....

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N.H. Gehani, H.V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model and implementation. In Proceedings of the 18th VLDB Conference, pages 327--338, Vancouver, 1992.

....and includes facilities for temporal information. Finite automata are the formal basis for describing activities. A prototype named COMPOSE for composite event detection has been implemented in concurrent C C 3 SPECIAL ISSUES 4 ( GJS93] References: AG89] AMC93] GJ91] GJ92] GJS92b] GJS92a] GJS93] JQ92] GJ96] Secondary: HW93] 2.14 REACH REACH is a project at the Technische 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 ....

.... events are described in: References: BJ93] CM93] GD93a] HK89] Ris89] SHP88] SJGP90] 3 SPECIAL ISSUES 6 Complex Event Detection Mechanisms to detect complex events are described in: References: BJ93] BL92] Cha92] CKAK94] CM93] GD93a] GD94] GHJ93] FD95] Jae95] GJS92a] GJS93] NTC92] RCBB89] SW92] SW95a] TJD95] Wid92a] Context Handling The handling of parameters for basic events, and context information for complex events are described in: References: BW95] Transactions and Concurrency The following papers address rule execution in the ....

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N. Gehani, H.V. Jagadish, and O. Shumeli. Composite event specification in active databases: Model and implementation. In Proc. 18th Int'l Conf. on Very Large Data Bases, Vancouver, Canada, Aug 1992. Annotation: This is a more formal description of [GJS92b].

....with activity extensions. First publications emphasize constraint and trigger management. The Ode rule language is very powerful and includes facilities for temporal information. Finite automata are the formal basis for describing activities. References: AG89] AMC93] GJ91] GJ92] GJS92b] GJS92a] JQ92] Secondary: HW93] 2.12 REACH REACH is a project at the Technische Hochschule Darmstadt, Germany. Influenced by HiPAC and DOM, it developed a core system named REACT, which implements a language comparable to Snoop (2.14) Two prototypes use O2 and ObjectStore as a platform in order to ....

.... Mechanisms to detect basic events are described in: References: BJ93] CM93] GD93a] HK89] Ris89] SHP88] SJGP90] Complex Event Detection Mechanisms to detect complex events are described in: References: BJ93] BL92] Cha92] CKAK94] CM93] GD93a] GD94] GHJ93] GJS92a] NTC92] RCBB89] SW92] Wid92a] Parameter Context Handling The handling of parameters for basic events, and context information for complex events are described in: References: CM93] Transactions The following papers address rule execution in the presence of regular transactions ....

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N. Gehani, H.V. Jagadish, and O. Shumeli. Composite event specification in active databases: Model and implementation. In Proc. 18th Int'l Conf. on Very Large Data Bases, Vancouver, Canada, Aug 1992. Annotation: This is a more formal description of [GJS92b].

....of constituent events, and an explosion of potential complex situations. Context parameters are a powerful restriction method. They specify relevant events by certain time intervals, transaction id, data state and other information available within the active databases [CM93] GD94] [GJS92] . Most systems provide a uniform set of context information for each basic event. Context arguments of complex situations are derived from basic information either by priorization or accumulation of arguments, depending on the event algebra operators. Event parameter processing often provides ....

....tasks depend on complex situation descriptions. Efficient management of event information requires an intelligent event and situation detection mechanism like in active databases. We do not want to develop yet another active database language, but propose a rule language like in HiPAC [MD89] Ode [GJS92], and SAMOS [GD94] The well known event conditionaction (ECA) structure of active rules is called (EC) A rule in [Jas94] which we will adopt in this paper, because it more precisely describes the semantics of complex situations. In AIMS the context condition C is tightly coupled with the event ....

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N.H. Gehani, H.V. Jagadish, O. Shmueli. Composite Event Specification in Active Databases: Model and Implementation. Proc. Int'l. Conference on Very Large Data Bases, August 23-27,

.... becomes even more complex, inasmuch as the issues of temporal databases and active rule languages are now combined and intertwined [21] In previous systems, the operational semantics of composite event detection has been defined using widely different frameworks, such as Finite State Automata [12], Petri Nets [11] or Event Graphs [4] Eventhough these systems have captured a great deal of the functionality required by active database applications, they are restricted by the limitations of their underlying This work was partially supported by NASA HPCC grant NAG 5 2225. formalisms. ....

....(f or g) Event History Figure 1: An FSM for the composite event E = f, g) 0 and sat denote the start and success states respectively. 2 1. FSMs do not support variables, and thus, they cannot detect parameterized events, which are essential in most real life applications. It is suggested in [12], that parameterized events are handled, by augmenting the states of an FSM with sets of partial variable bindings of the composite event that the FSM implements (detects) The resulting model surrenders the initial simplicity and intuitive appeal of FSMs, without providing a failproof formalism. ....

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N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model and implementation. In Proceedings of the 18th VLDB International Conference, pages 327--338, 1992.

....sophisticated event algebras (e.g. SNOOP, REACH, NAOS, CHIMERA [11] but there are not associated results on the expressiveness of these algebras which could be used as the basis for (global) reasoning about implication and equivalence of event queries. The event language of the system ODE [5], however, has been shown to have the power of regular expressions, but event consumption policies are not an explicit feature of the language. 10] proposes the use of Datalog 1S for expressing complex event queries. The advantage being that it has a well defined formal semantics. Such a language ....

N. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model and implementation. In VLDB'92, pages 327--338, 1992.

....between the temporal events A and A . The above defined wet of operators is minimal. Though, for making the authoring effort easier we have adopted two more operators: Event Modeling Composition The concept of event is defined in several research areas. In the area of Active Databases [GJS92, CM93] an event can be defined as an instantaneous happening of interest . An event is caused by some action that happens at a specific point in time and it may be atomic or complex. However, multimedia information systems widen the context of events as defined in the domain of active databases. In ....

N.H. Gehan, H.V. Jagadish, O. Shmueli, "Composite Event Specification in an Active Databases: Model & Implementation", Proceedings of VLDB Conference, 1992, pp. 327-338.

....(C) is satisfied on the database, then fire the action (A) which can be a database manipulation operation CHAPTER 1. INTRODUCTION 4 and or a procedural action. We propose that NM functions be specified as ECA rules. A number of ADB systems support composite event specification languages (CESL) GJS92a, GD94, CKAK94, MZ96] that allow temporal correlation of ADB events. But the existing CESLs are not well suited for the specification of event management requirements of NM. For example, composite event expression involving aggregation on event attributes, and persistent composite events, that ....

....happens. Composite events are specified using a composite event algebra which allows one to relate events occurring at different time points. Some examples of composite events are CHAPTER 3. ACTIVE AND TEMPORAL DATABASES 38 ffl three successive discount rate cuts without an intervening increase [GJS92a] happens at the events marked with as shown in Figure 3.2) ffl first rising threshold crossing event since the recent falling threshold crossing event [Has95] Figure 7.8) ffl server overload observed at all discrete points of a five minutes interval [Has95] Figure 7.9) ffl selling ....

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N. Gehani, H. Jagadish, and O. Shmueli. Composite event specification in active databases: Model and implementation. In Proceedings of the 18th International Conference on Very Large Data Bases, 1992.

....is the spatial instance, which refers to the spatial coordinates of a rectangle (x 1 , y 1 , x 2 , y 2 ) bounding an area of interest relative to the origin of an IMAP window. 2.3 The notion of events The concept of events is defined in several research areas. In the area of Active Databases [4, 5, 6] an event is defined as an instantaneous happening of interest [5] An event is caused by some action that happens at a specific point in time and may be atomic or composite. In multimedia literature events are not uniformly defined. In [16] events are defined as a temporal composition of objects, ....

....a rectangle (x 1 , y 1 , x 2 , y 2 ) bounding an area of interest relative to the origin of an IMAP window. 2.3 The notion of events The concept of events is defined in several research areas. In the area of Active Databases [4, 5, 6] an event is defined as an instantaneous happening of interest [5]. An event is caused by some action that happens at a specific point in time and may be atomic or composite. In multimedia literature events are not uniformly defined. In [16] events are defined as a temporal composition of objects, thus they have a temporal duration. In other proposals for ....

N.H. Gehani, H.V. Jagadish, O. Shmueli. "Composite Event Specification in an Active Databases: Model & Implementation". Proc. of VLDB Conference, 1992, pp. 327-338.

....executed, and if so, in which order If only one is to be executed, which one Also here, several solutions exist, depending on application. Date: 1st October 1996 Slide: 11 1 University of Skovde Technology Transfer: Active databases Event detection ffl An event is a happening of interest [ Gehani et al. 1992 ] ffl An event is an instantaneous (takes zero time) atomic (happens completely or not at all) occurrence [ Chakravarthy and Mishra, 1991 ] ffl Events can be further categorize into primitive events; and composite events Date: 1st October 1996 Slide: 12 University of Skovde ....

.... disjunction (OR) sequence . ffl There are various algorithms to detect that composite events have occurred, for example event graphs used in Snoop [ Chakravarthy and Mishra, 1991 ] Petri Nets used in SAMOS [ Gatziu and Dittrich, 1993 ] and Finite State Automata used in Ode [ Gehani et al. 1992 ] etc. Considering the combination of size and efficiency, event graphs is considered to be the best suited algorithm, although FSA is more efficient. Mellin, 1995, Deutsch, 1994] Date: 1st October 1996 Slide: 14 University of Skovde Technology Transfer: Active databases 14 Notes A ....

Gehani, N. H., Jagadish, H. V., and Shmueli, O. (1992). Composite event specification in active databases: Model and implementation. In Proceedings of the 18th VLDB Conference, Vancouver, British Columbia, Canada.

.... more complex, inasmuch as the issues of temporal databases and active rule languages are now combined and intertwined [19] Furthermore, the operational semantics of composite event detection in previous systems have been defined using widely different frameworks, such as Finite State Automata [11], Petri Nets [10] or Event Graphs [3] Eventhough these systems have captured a great deal of the functionality required by active database applications, they are restricted by the limitations of their underlying formalisms. Consequently, it is desirable that a general more abstract execution ....

....; En occur simultaneously. 4. fE 1 ; E 2 ; Eng : A disjunction of events. It occurs when at least one event among E 1 ; En occurs. 5. E : It occurs when not any instance of E occurs. A number of additional (derived) constructs may be defined in terms of the basic ones (see also [11]) Some of these are : ffl any j The disjunction of all basic events (of the types monitored) It occurs every time such an event occurs. ffl [E 1 ; E 2 ; En ] j (E 1 ; any; E 2 ; any; any; En ) Relaxed sequence. It consists of an instance of E 1 , followed later by an ....

[Article contains additional citation context not shown here]

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model and implementation. In Proceedings of the 18th VLDB International Conference, pages 327--338, 1992.

....system properties in the Internet) Conquer bridges this gap. Active Databases: Event Condition Action (ECA) systems are rule based programs in which an event triggers the testing of a condition, which in turn (if true) triggers an action. Most of active database systems [28] provide facilities [3, 21, 24, 7, 26, 9, 5] that support ECA rules referring to actions and events such as changes of database state. Some popular active database research prototypes include HiPAC [5] ODE [7] Postgres [26] Starburst [9] These systems support powerful rules and allow very general events, conditions, and actions, and ....

....condition, which in turn (if true) triggers an action. Most of active database systems [28] provide facilities [3, 21, 24, 7, 26, 9, 5] that support ECA rules referring to actions and events such as changes of database state. Some popular active database research prototypes include HiPAC [5] ODE [7], Postgres [26] Starburst [9] These systems support powerful rules and allow very general events, conditions, and actions, and therefore are difficult to implement efficiently. The result is fairly restricted implementations in practice. For example, typical built in triggers [11] in relational ....

N. Gehani, H. Jagadish, and O. Shmueli. Composite event specification in active database: Model and implementation. In Proceedings of ACM SIGMOD Conference, 1992.

....system properties in the Internet) Conquer bridges this gap. Active Databases: Event Condition Action (ECA) systems are rule based programs in which an event triggers the testing of a condition, which in turn (if true) triggers an action. Most of active database systems [29] provide facilities [3, 21, 24, 7, 26, 9, 5] that support ECA rules referring to actions and events such as changes of database state. Some popular active database research prototypes include HiPAC [5] ODE [7] Postgres [26] Starburst [9] These systems support powerful rules and allow very general events, conditions, and actions, and ....

....condition, which in turn (if true) triggers an action. Most of active database systems [29] provide facilities [3, 21, 24, 7, 26, 9, 5] that support ECA rules referring to actions and events such as changes of database state. Some popular active database research prototypes include HiPAC [5] ODE [7], Postgres [26] Starburst [9] These systems support powerful rules and allow very general events, conditions, and actions, and therefore are difficult to implement efficiently. The result is fairly restricted implementations (e.g. built in triggers [11] in relational database management systems ....

N. Gehani, H. Jagadish, and O. Shmueli. Composite event specification in active database: Model and implementation. In Proceedings of ACM SIGMOD Conference, 1992.

....constituent events of the event composition. In this paper, we discuss the stream based operator graph approach as used in Sentinel ( CKAK94] Kri94] Reach [BBKZ92] Adl [Beh95] Smile [Jae95] and others ( PW93] WC94] Variations of the graph approach are: finite automata in Ode ( GJS92b] GJS92a] and modified colored Petri nets in Samos ( Gat95] GD92] GD94] Operator Graphs. An operator graph is represented by a set of nodes and edges. An edge indicates a stream of totally ordered entries. Entries are appended at the end of the stream and received from the head. A node is either ....

N. Gehani, H.V. Jagadish, and O. Shumeli. Composite Event Specification in Active Databases: Model and Implementation. In Proc. 18th Int'l Conf. on Very Large Data Bases, Vancouver, Canada, Aug 1992.

....is simply a value in the appropriate history and delta relations. The specification and detection of both primitive and composite events merely consist of defining and evaluating queries over these relations. A history of primitive events can be used to define the semantics of event operators [12, 5]. However, such histories are not necessary for event detection. Alternatives are the Petri nets, finite automata and event graphs of SAMOS, Ode and Sentinel, respectively. Our events are specified in PFL which is computationally complete. In contrast, event expressions in Ode are reducible to ....

Gehani, N.H., Jagadish, H.V. and Schmueli, O. "Composite Event Specification in Active Databases: Model & Implementation", Proc. 18th VLDB Conference, Vancouver, 1992. pp 327-338.

....management policy, and in particular automated management. Much of the work on active databases has triggered actions which are similar to our obligation policies but these databases are not distributed, and the triggered actions are defined statically and cannot be changed without re compilation [12]. Lomita is a rule based language for programming the management layer in the Meta system [13] Lomita rules are of the form on condition do action , which is also similar to Jonscher s triggered actions, but there is no explicit subject or target they are defined implicitly. This paper has ....

Gehani, N., Jagadish, H., Shmueli O. (1992) Composite Event Specification in Active Databases: Model and Implementation, Proceedings of the 18th VLDB Conference, Vancouver, British Columbia, Canada.

....though they are published as such, e.g. the Java Distributed Event Specification. An investigation of these frameworks can be found, e.g. in [Car98] Also, we do not consider local event based procedures in operating systems, such as IPCs and interrupt handling. Active databases [CM93, CM94, GJS92a, GJS92b, GJS93] can serve as triggers for alerting services. The underlying model is based on ECA rules (Event ConditionAction) that can also be applied to alerting services, where the conditions are defined in the profiles and the action is sending the notification. The notion of events used ....

N. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases. In Proceedings of the 18th Conference on Very Large Databases, Morgan Kaufman pubs. (Los Altos CA), Vancouver, August 1992.

....infrastructures, relevant to human beings rather than notifications to other software components [2] The alerting services considered here are closer related to event action systems than to common event based infrastructures. An example of an event action system is Yeast [11] Active databases [9, 4] can serve as triggers for alerting services. The underlying model is based on ECA rules (Event Condition Action) that can also be applied to alerting services, where the conditions are defined in the profiles and the action is sending the notification. They cover the repository, the observer, ....

N. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases. In Proceedings of the 18th Conference on Very Large Databases, Morgan Kaufman pubs. (Los Altos CA), Vancouver, August 1992.

....elsewhere. However, we provide more detail on the semantics of event composition relative to transaction boundaries, as this has not been properly addressed in the literature. 3. 2 Event Composition Relative to Transaction Boundaries Events can be composed using either finite state automata [GJS92], colored) Petri nets [GD93b] or syntax graphs (e.g. CKA93] Deu94] A crucial issue for the architecture is the composition of events relative to transaction boundaries and the valid execution strategies of rules, depending on the kind of event. This issue has not been properly addressed ....

Gehani, N., Jagadish, H.V., Shmueli, O. Composite Event Specification in Active Databases: Model & Implementation, Proc. 18th VLDB, 1992.

....testing as to whether the action ought to be executed should be pushed into the condition part of a rule. This has the advantage of not blocking further event detection, and that the condition is processed as any other query. The other school of thought (represented among others by the Ode project [GJS92]) states that lightweight events cause too many rules to be triggered unnecessarily just to detect in the condition evaluation part that no action is required. Therefore, events are provided with additional conditions, so called guards, that allow the specification of rather complex conditions on ....

N.H. Gehani, H.V. Jagadish, and O.Shmueli. Composite event specification in active Databases: Model and Implementation. In Proc. of the 18th Intl. Conf. on Very Large Data Bases, Vancouver, Canada, August 1992.

....time (t s ) and end time (t e ) of that interval. Assume that x, y and z are properties of the same class. On January 1 1994, ff.y is modified to be 7, valid in [Jan 1 1994, Jan 8 1994) ff.x is modified to be 10, valid in 12 [Jan 1 1994, Jan 8 1994) only if the value of ff.z was more than 100 throughout the interval [Jan 1 1993, Jan 8 1994) Otherwise, ff.x is modified to be 22, valid in [Jan 1 1994, Jan 8 1994) Temporal action: A temporal action in a temporal data dependency results in the generation of values with bounded temporal validity that is a function of the temporal ....

....that is a function of the temporal validity of other values. For example, the operation clause x: y 3 valid in [t s , t e 4) defines an explicit valid time for the derivative. On January 1 1994, ff.y is modified to be 7, valid in [Jan 1 1994, Jan 8 1994) As a result, ff.x is modified to be 10, valid in [Jan 1 1994, Jan 12 1994) 5 Conclusion In this paper we have presented a language for the support of constraints in temporal active databases. Temporal constraints bound the temporal validity, and enable the support of temporal conditions and temporal actions, in addition to the ....

N. Gehani, H.V. Jagadish, and O. Shmueli. Composite event specification in active databases. In International Conference on Very Large Databases, Vancouver, Canada, Aug 1992.

....absolute time events and external (or abstract) events are also considered as primitive events. In general, most of the rule definition languages support additional before and after specifiers to refer to the begin or the end of the execution of an operation (or method) Composite events [GD94a, GJS92b] on the other hand, are events which are composed by several smaller events using event operators (e.g. disjunction, conjunction, sequence, history, closure) Of course, rule definition languages vary in the complexity of specifiable events because of different data models. Whereas AOODBSs ....

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite Event Specification in Active Databases. In L.-Y. Yuan, editor, Proc. of the 18th Int. Conf. on Very Large Data Bases (VLDB'92), Vancouver, Canada, pages 265--276. Morgan Kaufmann Publishers, August 1992.

.... 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 themselves in the active database field ....

....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 themselves in the active database field ( GJS92, NG92, GGD93, GD94, CM93, MPC96, CC96] but also in other fields (real time systems, artificial intelligence, etc. However, if most active systems differ on these aspects, they mainly differ on their behaviour. Large scale applications making intensive use of active rules are very few because the ....

O. Shmueli N.H. Gehani, H.V. Jagadish, Composite event specification in active databases: model & implementation, Proc. of the 18th Int. Conf. on Very Large Data Bases, September 1992.

....to do actions. Our system does not deal with freedom policies which might be used to permit human managers to override obligation policies, however we are not convinced of the need for liberties in management policy, and in particular automated management. Much of the work on active databases (Gehani, Jagadish and Shmueli, 1992) has triggered actions which are similar to our obligation policies but these databases are not distributed, and the triggered actions are defined statically and cannot be changed without re compilation. Lomita is a rule based language for programming the managementlayer in the Meta system ....

Gehani, N., Jagadish, H. and Shmueli, O. (1992). Composite event specification in active databases: Model and implementation, Proceedings of the 18th VLDB Conference,Van- couver, British Columbia, Canada.

....the spatial instance, which refers to the spatial coordinates of a rectangle bounding an area of interest (x 1 , y 1 , x 2 , y 2 ) relative to the origin of an IMAP window. 2.3 The notion of events The concept of events is defined in several research areas. In the area of Active Databases [Ga94, GJS92a, GJS92b, CM93] an event is defined as an instantaneous happening of interest [GJS92a] An event is caused by some action that happens at a specific point in time and may be atomic or composite. In the multimedia literature events are not uniformly defined. In [SW95] events are defined as a ....

....an area of interest (x 1 , y 1 , x 2 , y 2 ) relative to the origin of an IMAP window. 2.3 The notion of events The concept of events is defined in several research areas. In the area of Active Databases [Ga94, GJS92a, GJS92b, CM93] an event is defined as an instantaneous happening of interest [GJS92a] An event is caused by some action that happens at a specific point in time and may be atomic or composite. In the multimedia literature events are not uniformly defined. In [SW95] events are defined as a temporal composition of objects, thus they have a temporal duration. In other proposals for ....

N.H. Gehani, H.V. Jagadish, O. Shmueli, "Composite Event Specification in an Active Databases: Model & Implementation". Proceedings of VLDB Conference, 1992, pp. 327338.

....with the object Film occurs, we want to go back to the beginning. rule restart = Film.ScarletDisappears Film Source.gotoframe(0) We can also combine primitive events into ordered combinations using certain operators. We have borrowed a general approach from the field of active databases [4] which is ideally suited to this form of application. We can express any temporal or spatial combination. For example we can specify with relation to object Film that if the area where Scarlet appears is clicked on between the events which indicate she is on screen then pause the video and display ....

N. H. Gehani et al., "Composite Event Specification in Active Databases- Model and Implementation ", Proceedings of the 18th VLDB Conference, pp. 327-338, 1992.

....with activity extensions. First publications emphasize constraint and trigger management. The Ode rule language is very powerful and includes facilities for temporal information. Finite automata are the formal basis for describing activities. References: AG89] AMC93] GJ91] GJ92] GJS92b] GJS92a] JQ92] Secondary: HW93] 2.12 REACH REACH is a project at the Technische Hochschule Darmstadt, Germany. Influenced by HiPAC and DOM, it developed a core system named REACT, which implements a language comparable to Snoop (2.14) Two prototypes use O2 and ObjectStore as a platform in order to ....

.... Detection Mechanisms to detect basic events are described in: References: BJ93] CM93] GD93a] HK89] Ris89] SHP88] SJGP90] Complex Event Detection Mechanisms to detect complex events are described in: References: BJ93] BL92] Cha92] CKAK94] CM93] GD93a] GD94] GHJ93] GJS92a] NTC92] RCBB89] SW92] Wid92a] Parameter Context Handling The handling of parameters for basic events, and context information for complex events are described in: References: CM93] Transactions The following papers address rule execution in the presence of regular transactions within ....

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N. Gehani, H.V. Jagadish, and O. Shumeli. Composite event specification in active databases: Model and implementation. In Proc. 18th Int'l Conf. on Very Large Data Bases, Vancouver, Canada, Aug 1992.

....= e where e is any event observable by the database system. This is the most general class of coherency conditions and its realization is tightly related to mechanisms developed in active databases [13] A formal syntax for specifying events is beyond the scope of this paper but can be found in [19, 33]. 3 Modeling a replicated database In section 3.1 we present a queueing network model for replicated databases and sketch how to obtain important performance criteria to judge relaxed coherency in section 3.2. It is based on the coherency index (k) introduced in section 2.2.2. So it is generally ....

N.H. Gehani, H.V. Jagadish, O. Shmueli: "Composite Event Specification in Active Databases: Modell & Implementation", VLDB 92, pages 347-362.

....as diverse scheduler classes. ffl Choice among several prefabricated 6 detectors. The detection of complex events (e.g. conjunction or sequence of two events or the negation of an event; 10] is a complex procedure where different approaches like Petri Nets [11] trees [5, 6] and automata [12] have been examined. The ubiquitous trade off between efficiency (i.e. detection time) and functionality (e.g. conservation of event parameters with implication to the possible strategies) prominently manifests itself in this subject. Different detection strategies are implemented, so that the ....

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite Event Specification in Active Databases. In Proc. of the 18th Intl. Conference on Very Large Databases, Vancouver, August 1992.

....relations comparing condition transaction and action transaction have to be provided. Class external rules call methods which are synchronized with other methods and rules by themselves. The execution of multiple rules triggered by the same event is handled by means of priorities. 2. 3 Ode Ode [Geha92a, Geha92b] is a database system based on the database programming language O , which is an extension to the object oriented programming language C . O extends C by providing database facilities such as creating and manipulating persistent and versioned objects, and associating constraints and triggers ....

N. H. Gehani, H. V. Jagadish, O.Shmuheli, Composite Event Specification in Active Database Systems, Proc. of the 18th Int. Conference on VLDB, August 1992

....basis, uniform mechanisms for composite event detection can be provided. Such mechanisms have been used widely in the area of active databases. Techniques developed in this field are not fully appropriate for our problem. For example, the grammar and finite state machine approach described in [GJS92] does not allow concurrent monitoring. Once one sequence is being checked for, the monitor is busy until it has finished that detection. Other approaches are more complex to implement [CM93, GD94] and are designed for a centralised database. These do not directly address issues required for a ....

N.H. Gehani, H.V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model & implementation. In Proceedings of the 18th VLDB Conference, Vancouver, British Columbia, Canada, 1992.

....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 systems mentioned above use C , except ADAM which is based on Prolog. Few ....

....in time, and not over a period of time. Further, there is no such thing as an event being half done, either it occurs or it doesn t. The nature of an event is however not clearly defined within the database area. An example of such an informal definition is: An event is a happening of interest. GJS92a] Although no formal definition is given, many examples of what type of happenings that should be considered as an active database event have been given, for example in [CM91] Events can be divided into primitive events and composite events. Primitive events are simple events detected in the ....

[Article contains additional citation context not shown here]

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model and implementation. In Proceedings of the 18th VLDB Conference, Vancouver, British Columbia, Canada, 1992.

....of relationship can not be expressed by most event specification languages in literature. Finally, we develop a detection algorithm that uses a tree structure to efficiently monitor composite events. 1 1 Introduction Recently rule system have been applied in various database research efforts [CW91, SPAM91, SK91, Cho92, GJS92, GD93, SW95]. A problem in study of rule systems is the specification of the events. Since the early study of this problem by [DBB 88] many proposals have been seen in literature. Research efforts studying event specification are forced in the design of specification languages, event semantics, expressive ....

....to general semantics, Chakravarthy and Mishra introduced four other types of events semantics, namely, Recent, Chronicle, Continuous, and Cumulative. Expressive power handles how capable a specification language is of expressing composite events. Clearly, the more expressive, the better. In [GJS92], Gehani, Jagadish and Shmueli designed a language reaching the expression power of a regular language. Gatziu and Dittrich, authors of [GD93] use Petri nets to detect composite events, hence their language potentially has the expressive power of the Petri nets. Chakravarthy and Mishra used a ....

[Article contains additional citation context not shown here]

GEHANI, N. H., JAGADISH, H. V. AND SHMUELI, O., Composite event specification in active databases: model & implementation, VLDB'92, pp.327-338.

....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 : ffl ex ecution des r egles de fa con s equentielle en mode ....

N. Gehani, H.V. Jagadish, O. Shmueli. Composite Event Specification in Active Databases: Model & Implementation. In Proceedings of the Eighteenth International Conference on Very Large Data Bases, pages 327--338, Vancouver, British Columbia, August 1992.

.... 88, MD89, BM91, SSU91, GJ91, LLPS91, SK91] In an active database, a trigger fires when an event of interest happens and some condition is satisfied. Most efforts have focussed on the trigger firing mechanism and the execution of the triggered action. However, recent work [DHL91, CM91, GJS92b, GJS92a] has recognized the importance of event specification. Of special interest is the specification of composite events, which are constructed from (simpler) basic events. Events usually have attributes. For instance, an insert event has information regarding the specific relation (or object ....

....methods are invoked. It is even possible for events to take as attributes arbitrary values (computed) from the database at the time at which the event occurs. Author s current affiliation: Technion Israel Institute of Technology, Haifa 32000 Israel. 1 It has been argued [DHL91, CM91, GJS92b, GJS92a] that the specification and detection of composite events is important for an active database. Here, a composite event comprises a sequence of constituent primitive events. The attributes of a composite event must be derived from the attributes of the constituent primitive events. These ....

[Article contains additional citation context not shown here]

Narain Gehani, H. V. Jagadish, and Oded Shmueli. Composite event specification in active databases: Model and implementation. In Proceedings of the Eighteenth International Conference on Very Large Databases (VLDB), pages 327--338, Vancouver, Canada, August 23-27 1992.

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Narain H. Gehani, H. V. Jagadish, and Oded Shmueli. Composite event specification in active databases: Model & implementation. In Li-Yan Yuan, editor, Proceedings of the Intl Conference on Very Lage Data Bases (VLDB), pages 327--338, Vancouver, Canada, August 1992. Morgan Kaufmann.

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N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model & implementation. In L.-Y. Yuan, editor, Proceedings of the 18th International Conference on Very Large Data Bases (VLDB'92), pages 327--338, Vancouver, Canada, Aug. 1992. Morgan Kaufmann.

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N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite Event Specification in Active Databases: Model & Implementation. In Proceedings of the 18th International Conference on Very Large Databases (VLDB), 1992.

No context found.

N. Gehani, H. Jagadish, and O. Shmueli. Composite Event Specification in Active Databases: Model & Implementation. In Proc. of VLDB, pages 327--338, August 1992.

No context found.

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model & implementation. In Proceedings of the Intl. Conference on Very Large Data Bases (VLDB), 1992.

No context found.

N. Gehani, H. Jagadish, and O. Shmueli. Composite Event Specification in Active Databases: Model & Implementation. In Proc. of VLDB, pages 327--338, August 1992.

No context found.

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model and implementation. In Proceedings of the 18th International Conference on Very Large Data Bases, 1992.

No context found.

N. H. Gehani, H. V. Jagadish, and O. Shmueli. Composite event specification in active databases: Model implementation. In Proceedings of the 18th International Conference on Very Large Databases, Vancouver, British Columbia, Canada, 1992.

No context found.

Gehani, N.H., Jagadish, H. V. and Shmueli, O. Composite event specifi- cation in active databases: Model and implementation. In Proceedings of the 18th VLDB International Conference (Vancouver, Canada, August 1992), 327-338.

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