S. Gatziu: Events in an Active, Object-Oriented Database System. PhD-Thesis. Dr. Kovac, Nov. 1994.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....do not consider complex events and do not allow that at a point in time rules may be triggered more than once and may be executed as often as being triggered. For the detection of complex events Petri nets or higher level Petri nets like Coloured Petri nets have been shown to be suitable [Gat94, Zim95]. Petri nets are used to model possible rule execution traces which are analysed for termination. The information about the interactions between the rules may be taken directly from the rule definitions or from the results of other rule termination analysis techniques, as e.g. BW94, VS94] As the ....

Stella Gatziu. Events in an Active, ObjectOriented Database System. Phd-Thesis. Dr. Kovac, November 1994.

....language features like orthogonality, homogeneity, and symmetry. Moreover, the set of language constructs provided is sometimes too overloaded (overlapping) so that the same situation can be described in different ways. In most event algebras, such as those defined in HiPAC ( DaBC96] SAMOS ([Gatz94]) Ode ( GeJS92] Chimera ( MePC96] and NAOS ( CoCo96] event operators are the only way to specify the semantics of complex events. This leads to a confusion of concepts that makes the understanding of an inherently complex area even more difficult. A number of peculiarities and ....

....all these types. Axiom 4: The occurrence time of the terminator of a complex event instance always represents the occurrence time of the complex event as well. Axiom 5: Events can occur simultaneously. Thus, different event instances may get the same event occurrence time. Some models (e.g. [Gatz94], CKAK94] exclude such a behavior. However, we believe that such restrictions are not adequate as a database and a temporal event may occur simultaneously or one single event may trigger a number of other (complex) events, which may even be of the same type 3 . Axiom 6: For reasons of ....

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S. Gatziu: Events in an Active, ObjectOriented Database System. PhD-Thesis. Dr. Kovac, Nov. 1994.

.... 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 a leaf, a root, or an operator node. A detection ....

....BEFORE operator produces the composition of A:14 and B:17, bearing the time stamp 17. ticks LEAF (A) LEAF (B) BEFORE 1 A:14 2 B:17 3 (A:14; B:17; 17) Table 1. Example table for BEFORE(A,B) Composite event detection in ADBMS so far is sequential and centralized ( Beh95] BBKZ92] CKAK94] Gat95] GD92] GJS92b] Jae95] Kri94] PW93] WC94] For composite events the detection process advances step by step with each constituent event. The composite event detector accepts events in a totally ordered stream. For the sequential synchronized execution of the operator graph, we assume ....

S. Gatziu. Events in an Active, Object-Oriented Database System. PhD thesis, Univerisity of Zurich, Switzerland, 1995.

....and give conclusions and directions for future research in Section 7. 2 Related Work The rule subsystems of the existing active and or object oriented DBMSs (e.g. POSTGRES [42] Ariel [21] HiPAC [13] active OODB [6] ADAM [15] DOM [7] Starburst [49] Ode [19] Alert [1] and SAMOS [18]) use either priorities, to define the control structures among rules, or support no rule control mechanism at all. However, the priority based control mechanism is not flexible and expressive enough to meet the requirement of structured rule execution found in some advanced DB applications. As ....

S. Gatziu and K. R. Dittrich. SAMOS: an active, object-oriented database system. in IEEE Quarterly Bulletin on Data Engineering, 15(1):23--26, December 1992.

....the occurrences of the events, evaluating the condition when the event is signaled, and executing the action if the condition evaluates to true. A significant body of work exists on rules and rule processing in a DBMS. However, the event component of rules has received attention only recently [4, 5, 14, 10] and perhaps is the least understood compared to the condition and action components. Conditions and actions can be viewed as side effect free queries and transactions, respectively. This work is supported, in part, by the National Science Foundation IRI 9011216, by the Office of Naval Research ....

....relevant to application classes as well as for its use in active databases. To accommodate this, we introduce the notion of parameter contexts as a mechanism for precisely restricting the occurrences that make a composite event occur as well as for computing its parameters. Ode [14, 13] and Samos [10, 11] address event specification and detection in the context of active databases. Although there are some differences between Snoop, Ode, and Samos in the event specification language (for example, Samos has a Times operator for defining the occurrence of n events in an interval and Ode has a ....

S. Gatziu and K. R. Dittrich. SAMOS: an Active, Object-Oriented Database System. in IEEE Quarterly Bulletin on Data Engineering, 15(1-4):23--26, December 1992.

....we partition the problem space into classes along two distinct dimensions that quantify the level of cooperation required. Based on the architecture provided in [CKNT93] we describe the details of realizing that architecture using the reactive paradigm proposed by the active database community [GD92, GD93, GJ91, GJS92b, GJS92a, CM94, CAMM94, Lee96, Lee96, CKAK94, BL92, BZBW95] 2 The Problem Domain Extant approaches to cooperative problem solving can be categorized by mapping them along a single dimension that indicates their inherent degree of cooperation: from none to the most general ....

S. Gatziu and K. R. Dittrich. SAMOS: an Active, Object-Oriented Database System. in IEEE Quarterly Bulletin on Data Engineering, 15(1-4):23--26, December 1992.

....event instance selection defines which events are bound to a complex event, and the event instance consumption determines when events become invalid, i.e. they cannot be considered for the detection of further complex events. In most event algebras, such as those defined in HiPAC [DBM88] SAMOS [Gat94] Ode [GJS92] Chimera [MPC96] and NAOS [CC96] event operators are the only way to specify these different dimensions. This leads to a confusion of concepts that makes the understanding of an inherently complex area even more difficult. We will show that currently there are a number of ....

...., is triggered twice. In Snoop [Mis91, CKAK94] as we will show later, this sequence causes e 1 ;e 3 to be triggered twice while e 1 ; e 2 ;e 3 is triggered only once. 1 The terms event consumption or consumption mode have been used previously in the literature (see, e.g. BBKZ93, Day95, DGG95, Gat94] However, in these papers the authors essential meaning corresponds to aspects of our dimension event instance selection and thus seems to be misleading. The literature provides relatively few studies of the subdivision of the semantics of complex events. In Snoop [Mis91, CKAK94] parameter ....

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Stella Gatziu. Events in an Active, ObjectOriented Database System. Phd-Thesis. Dr. Kovac, November 1994.

.... reset test 2 t 1,1 p p p 1,0 2,0 3,0 t 1,3 3,3 2,3 1,0 p p 2,0 2,2 2,5 2,1 3,1 p p 1,1 p t 1,6 2,6 3,6 Figure 13: Example of the Petri net as constructed by our algorithm part of a rule more precisely (modeling of a sequential and conditional event generation) or modeling complex events (see e.g. [Gat94, Zim95]) 8 Comparison between the two techniques In this paper we have shown, that the rule semantics considered by the trac method can easily be expressed by Petri nets of the type PN PKB . For these kind of models we get the same quality of results as the tracmethod does. For the extended models as, ....

Stella Gatziu. Events in an Active, Object-Oriented Database System. PhdThesis. Dr. Kovac, November 1994.

....that automatically collect and combine constituent events of the event composition. In this paper, we discuss the operator graph approach as used in SENTI NEL [5,15] REACH [2] ADL [1] SMILE [13] and others [18,25] Finite automata in ODE [11,12] and modified colored Petri nets in SAMOS [8,9,10] are variations of the detection technique based on operator graphs. All approaches are sequential. Event detection is centralized. During runtime, the Active DBS receives atomic events and collects those in a timely ordered history. For example, a history of event instances of atomic types A, B, ....

S. Gatziu. Events in an Active, Object-Oriented Database System. Ph.D. Thesis, University of Zurich, Switzerland, Verlag Dr. Kovac, 1995.

....events and computing their parameters in the recent parameter context. Our language subsumes the events supported in the extant active database systems including Ariel [15, 5] Interbase ( 18] Postgres ( 24] 23] Starburst [25] 3] HiPAC ( 4] 8] ADAM ( 9] Ode [14] and Samos ([12]) OSAM ( 19, 22] Table 7 compares Snoop with the events supported in various systems 8 . The emphasis in Snoop [20, 6] and Sentinel [5, 2] is quite different from that taken in [17] and [21] respectively; Snoop extends the event specification language in a model independent manner and ....

S. Gatziu and K. R. Dittrich. SAMOS: an Active, Object-Oriented Database System. in IEEE Quarterly Bulletin on Data Engineering, 15(1-4):23--26, December 1992.

....;e 3 is triggered only once. Literature does only provide relatively few attempts for the subdivision of the semantics of complex events. In Snoop [CKAK94] parameter contexts were introduced. They are responsible for the determination of the set of events that are bound to complex events. SAMOS [Gat94] copes with this semantics by the introduction of two additional operators called and last , which select the oldest ( or most recent event ( last ) out of a set of events. In the following section we introduce some basic definitions which are used for the definition of our meta model ....

....of some data is an example for an event. Definition 2: For this paper we assume an equi distant discrete time domain TD having 0 as the origin and consisting of points in time represented by non negative integers. In general events should be permitted to occur simultaneously. Some models (see [Gat94, CKAK94] exclude such a behaviour. However we believe that such restrictions are not adequate as one single event may trigger a number of other (complex) events, which may even be of the same type 1 . Definition 3: In the system a concrete event is represented by an event instance (EI) which ....

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Stella Gatziu. Events in an Active, ObjectOriented Database System. Phd-Thesis. Dr. Kovac, November 1994.

No context found.

S. Gatziu, K.R. Dittrich. SAMOS. An Active, Object-Oriented Database System. In [16].

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S. Gatziu, K.R. Dittrich: SAMOS: An Active, Object-Oriented Database System. In [7].

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S. Gatziu: Events in an Active, Object-Oriented Database System. PhD-Thesis. Dr. Kovac, Nov. 1994.

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Gatziu, S.: Events in an Active, Object-Oriented Database System, Hamburg: Dr. Kovac 1995.

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