H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, K. Salem, Modeling Long-Running Activities as Nested Sagas, IEEE Bulletin of the Technical Committee on Data Engineering, 14 (1), 1991  Home/Search   Document Not in Database   Summary   Related Articles   Check

....of database 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 ....

....be possible that the application is not aware of the underlying active capabilities, and, thus, the functionality realized by ECA rules does not directly influence the application. According to this decision, some transaction modes which have considerable influence on the application such as vital [Garc91] could be allowed or not. Whatever transaction modes will finally be provided, their combined usage for distinct components of a composite event have to be restricted in order to prevent indeterminism and inefficiency. Besides that, it would also be useful to develop some kinds of design ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, K. Salem, Modeling Long-Running Activities as Nested Sagas, IEEE Bulletin of the Technical Committee on Data Engineering, 14 (1), 1991

....transaction management. There are two challenges to achieve this integration. Firstly, due to their asynchronous nature, agents are best suited to be engaged in long lived activities. It must be investigated, which transaction models meet these requirements, where Contracts [WaeReu92] and Sagas [GarciaEA91] seem to be a good starting point. Secondly, at least parts of the agent state must be made recoverable. Current approaches to integrate mobile entities and transactions, such as Java Database Connection (JDBC, see [HaCaFi97] and Java Transaction Service (JTS, see [JavaSoft97] only consider ....

H. Garcia-Molina, D. Gawlick, J. Klein, et al. "Modeling Long-Running Activities as Nested Sagas", Data Engineering Bulletin 14(1): 14-18 (1991) .

....of a production line. At present, this information is all embedded in application programs, as described in the next subsection. It is worth noting that the idea of assigning states to materials contrasts with transactional workflow, in which states are assigned to long running activities (e:g: [48, 1, 58, 21]) This difference might be resolved if each material were associated with a single long running activity. This activity would exist as long as the material is being processed, and would correspond to the sequence of workflow steps that process the material. In this case, material state and ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, and K. Salem. Modeling long-running activities as nested sagas. Bulletin of the Technical Committee on Data Engineering (IEEE Computer Society), 14(1), March 1991.

....the greater functionality and performance required by complex applications. These include nested transactions [76, 89] multi level transactions [77, 11] cooperative transactions [60] compensating transactions [61] recoverable communicating actions [128] split transactions [90] and sagas [44, 45]. Each of these transaction models has different semantics with respect to visibility, consistency, recovery and permanence in their attempt to be useful for various complex applications. As an example, a nested transaction is composed of subtransactions that may execute concurrently. ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, and K. Salem, "Modeling LongRunning Activities as Nested Sagas," IEEE Technical Committee on Data Engineering, 14(1):14-18, March 1991.

....(t j WCD t i ) if t i commits, t j can begin executing after t i commits; i.e. Begin t j 2 H) Commit t i 2 H) Commit t i Begin t j ) Let us look at further examples of structure related transaction correctness properties. In the transaction model proposed in [Buchmann, 1990, Garcia Molina, 1991] a parent can commit only if its vital children commit, i.e. a parent transaction has an abort dependency on its vital children t v (t p AD t v ) Child transactions may also have different dependencies with their parents if the transaction model supports various spawning or coupling modes ....

Garcia-Molina H., D. Gawlick, J. Klein, K. Kleissner, and K. Salem. (1991) Modeling Long-Running Activities as Nested Sagas. Bulletin of the IEEE Technical Committee on Data Engineering, 14(1):14--18.

....subtransactions, say T k , fails, then committed subtransactions T 1 , T k Gamma1 are undone by executing compensating subtransactions CT k Gamma1 , CT 1 . Sagas relax the full isolation requirements and increase inter transaction concurrency. An extension allows the nesting of Sagas [Garcia Molina et al. 1991]. Nested Sagas provide useful mechanisms to structure steps involved within a long running transaction into hierarchical transaction structures. This model promotes a relaxed notion of atomicity whereby forward recovery is used in the form of compensating transactions to undo the effects of a ....

Garcia-Molina, H., Salem, K., Gawlick, D., Klein, J., and Kleissner, K. (1991). Modeling Long-Running Activities as Nested Sagas. IEEE Data Engineering Bulletin, 14(1).

...., fails, then committed subtransactions T 1 , T k Gamma1 are undone by executing compensating subtransactions CT k Gamma1 , CT 1 . Sagas relax the full isolation requirements and increase inter transaction concurrency. An extension allowing the nesting of sagas has been proposed in [20]. Split and Join Transactions [40] were designed for open ended activities characterized by uncertain, but usually very long duration, unpredictable development, and interaction with other activities. A transaction may split into two separate transactions (the resources are divided) and later ....

H. Garcia-Molina, K. Salem, D. Gawlick, J. Klein, and K. Kleissner. Modeling Long-Running Activities as Nested Sagas. Data Engineering Bulletin, 14 (1), March 1991.

....These applications exhibit new requirements in terms of control flow, distribution and cooperation which call for more flexible transaction management. An important flexible transaction model is that of nested transactions proposed by Moss [12] which has been the basis for many extensions [7, 19, 4, 20, 21]. A nested transaction is a tree of transactions with a top level transaction as root and subtransactions as leaves or intermediate nodes. A sub transaction can either commit or abort, but commitment will take effect only when the top level transaction commits. Thus, the top level transaction has ....

Hector Garcia-Molina. Modeling long-running activities as nested sagas. Data Engineering, 14(1):249-- 259, March 1991.

....These applications exhibit new requirements in terms of distribution, cooperation and long duration which call for more flexible transaction management. An important flexible transaction model is that of nested transactions proposed by Moss [13] which has been the basis for many extensions [8, 20, 4, 21, 22]. A nested transaction is a tree of transactions with a top level transaction as root and subtransactions as leaves or intermediate nodes. A sub transaction can either commit or abort, but commitment will take effect only when the top level transaction commits. Thus, the top level transaction has ....

Hector Garcia-Molina. Modeling long-running activities as nested sagas. Data Engineering, 14(1):249-- 259, March 1991.

....transaction without any requirement for compensation. This example suggests that analogously to the different isolation modes discussed in the context of basic task integration, a variation task may also require different modes for atomicity. This situation is analogous with nested transactions [22, 11, 12] where typically subtransactions have to satisfy ACID properties when executed alone, but the nested transaction does not necessary have to be fully isolated. To capture the facility of varying execution requirements of a task we introduce the following execution modes: DEFINE ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, and K. Salem. Modeling long-running activities as nested sagas. IEEE Data Engineering Bulletin, 14(1), March 1991.

....that the predecessor subtransaction has completed) and that commit is allowed upon completion of a subtransaction. This specification causes the transaction to behave as a set of disjoint subtransactions that commit serially. Such a structure could also be used to model a long duration transaction [10]. The transaction structure also allows the specification of concurrent or parallel executions (Figure 2b) Subtransactions can have the precondition that all must begin at the same time. Conversely, the structure allows specification of a set of disjoint parallel subtransactions being ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, and K. Salem. Modeling long-running activities as nested sagas. Bulletin of the IEEE Technical Committee on Data Engineering, 14(1), March 1991.

....of workflow applications, it is vital to have a model that is powerful enough to support the specifications of not only the common features possessed by most workflow applications but also some special features arising from individual specifications. Recently, a number of models have been proposed [4,5,6,7,8,9,10,15,16] which may fit various applications. One crucial requirement in a workflow specification is the identification of the requirements for the control data flow among the participating tasks. In some literatures, these flows are supported by the concept of dependency. A dependency imposes certain ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, and K. Salem, "Modeling long-running activities as nested sagas", IEEE Data Engineering Bulletin, 14(1), Mar ch 1991.

....requirement matches more to the traditional transaction without any requirement for compensation. This example suggests that analogously to the different isolation modes discussed earlier, a task may also require various modes for atomicity. This situation is analogous with nested transactions [16, 8, 9] where typically subtransactions have to satisfy ACID properties when executed alone, but the nested transaction does not necessary have to be fully isolated. To capture the facility of varying execution requirements of a task we introduce the following execution modes: prepare mode, compensation ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, and K. Salem. Modeling long-running activities as nested sagas. IEEE Data Engineering Bulletin, 14(1), March 1991.

....c would be incorrect and must therefore be prevented by the L0 concurrency control. If, in a two level system, the conflict relation at the higher level is em 6 Chapter 13. Multilevel Transactions and Open Nested Transactions pty, then we arrive at the special case of sagas [GS87] see also [GGKKS91] for nested sagas) Sagas are based on the assumption that all high level operations (called steps ) are commutative. Therefore, a transaction can in fact be decomposed into a sequence of independent subtransactions. That is, it is sufficient to serialize the resulting subtransactions, and no ....

Garcia-Molina, H., Gawlick, D., Klein, J., Kleissner, K., Salem, K. Modeling Long-Running Activities as Nested Sagas. IEEE Data Engineering Vol.14 No.1, 1991.

....is drawn into consideration as a criterium for commutativity at the higher levels of the execution trees. In S transactions the main focus is on autonomy and the recovery is based on compensation [GM83, KLS90, Vei90] as is the case also with open nested transactions. Sagas [GMS87, GMDGKS90, GMDGKS91] are simple Stransactions and the Flex Transaction Model [BEK93] also bears some similarities. Split transactions [PH88, KP92] represent a novel view of how to dynamically restructure transactions. This idea might be of interest also for workflows. Transaction Specification and Management ....

Hector Garcia-Molina, Johannes Klein Dieter Gawlick, Karl Kleissner, and Kenneth Salem. Modeling long-running activities as nested sagas. IEEE Data Engineering Bulletin, 14(1), March 1991.

....the workload for the DBMS. A sample graph is given in [2] one that forms the basis of the workload for the LabFlow 1 benchmark. It is worth noting that the idea of assigning states to materials contrasts with transactional workflow, in which states are assigned to long running activities (e:g: [22, 26, 9]) This difference might be resolved if each material were associated with a single long running activity. This activity would exist as long as the material is being processed, and would correspond to the sequence of workflow steps that process the material. In this case, material state and ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, and K. Salem. Modeling long-running activities as nested sagas. Bulletin of the Technical Committee on Data Engineering (IEEE Computer Society), 14(1), March 1991.

....different programming techniques and a different concept of duration. In the literature, there are several suggestions for new execution models to allow control of long duration transactions which may consist of an arbitrary number of subtransactions e.g. nested, chained, conditional. Gar87] [Gar91], Reu90] Another approach is to use relaxed transaction models [Chr93] Geo95] CHAPTER II 36 2.5.1 LINEAR SAGAS Linear Sagas [Gar87] were originally proposed to solve the problem of long lived transactions. The model was later extended to parallel, nested, and generalized Sagas ....

....[Reu90] Another approach is to use relaxed transaction models [Chr93] Geo95] CHAPTER II 36 2.5.1 LINEAR SAGAS Linear Sagas [Gar87] were originally proposed to solve the problem of long lived transactions. The model was later extended to parallel, nested, and generalized Sagas [Gar90][Gar91]. The Saga model allows a transaction to release resources before commit time. A Saga transaction is a sequence of sub transactions (Saga steps) that can be interleaved with other transactions. The Saga step is a separate transaction with ACID properties. Each step also has a defined compensating ....

Garcia-Molina, Gawlick, D., Klein, J., Kleissner, K., Salem, K., Modeling Long-Running Activities as Nested Sagas, Bulletin of the Technical Committe on Data Engineering, IEEE, 14(1), March 1991. Compcon, 1991.

.... multiparent subtransactions, inheritance of locks 1 Introduction 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 [1, 7, 8, 16]. Active database capabilities are now finding their way into many of the most popular commercial database management systems. In contrast to conventional database management systems, active database management systems perform certain operations automatically, either in response to certain events ....

....as a message event. Incorporating other kinds of simple events such as time events and external events is part of ongoing research. 2. 1 Nested Transactions for Simple Events Most of the execution models of existing active object oriented database systems are based on the nested transaction model [3, 4, 6, 8]. Note that in the following, if not stated otherwise, the term nested transactions stands for closed nested transactions [11] The nested transaction model is particularly appropriate for active systems due to the following reasons [13, 20] First, its structure accommodates nicely the ....

H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner and K. Salem, "Modeling Long-Running Activities as Nested Sagas, " IEEE Bulletin of the Technical Committee on Data Engineering, vol. 14, no. 1, 1991.

....these requirements are specified via axioms that express the dependencies that are formed when transactions execute according to the given model. We first look at some simple examples of structure related transaction correctness properties. In the transaction model proposed in [Buchmann, 1990, Garcia Molina, 1991] a parent can commit only if its vital children commit, i.e. a parent transaction has an abort dependency on its vital children t v (t p AD t v ) Child transactions may also have different dependencies with their parents if the transaction model supports various spawning or coupling modes ....

Garcia-Molina H., D. Gawlick, J. Klein, K. Kleissner, and K. Salem. (1991) Modeling Long-Running Activities as Nested Sagas. Bulletin of the IEEE Technical Committee on Data Engineering, 14(1):14--18.

....and release their resources when completed. Long duration transactions are used for many scientific and engineering applications [36] It is also shown that the log and state information needed for compensation can be stored within the same application database. The notion of sagas is extended in [25] to nested sagas, where a subtransaction may be further decomposed into steps that are compensatable. Other ideas for using semantic atomicity for coping with long lived activities are discussed in [22] 56] One issue that we have not addressed in this section is that of the design of ....

H. Garcia-Molina, K. Salem, D. Gawlick, J. Klein, K. Kleissner, Modeling Long-Running Activities as Nested Sagas, Database Engineering, Vol. 14, No. 1, March, 1991.

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Garcia-Molina, H., Gawlick, D., Klein, J., Kleissner, K., and Salem, K. Modeling Long-Running Activities as Nested Sagas. Bulletin of the IEEE Technical Committee on Data Engineering, 14(1):14--18, 1991.

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H. Garcia-Molina, G. Gawlick, J. Klein, K. Kleissner, and K. Salem. Modeling Long-Running Activities as Nested Sagas. Bulletin of the Technical Committee on Data Engineering, 14(1), 1991. IEEE Computer Society.

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H. Garcia-Molina, D. Gawlick, J. Klein, K. Kleissner, and K. Salem. Modeling long-running activities as nested sagas. Technical Report CS-TR-247-90, Dept. of Computer Science, Princeton U., February 1990.

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Garcia-Molina, H., Gawlick, D., Klein, J., Kleissner, K., and Salem, K. Modeling Long-Running Activities as Nested Sagas. Bulletin of the IEEE Technical Committee on Data Engineering, 14(1):14--18, 1991. 24 Chapter 10. Correctness Criteria and Concurrency Control

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Hector Garcia-Molina, Dieter Gawlick, Johannes Klein, Karl Kleissner, and Kenneth Salem. Modeling long-running activities as nested sagas. IEEE Data Engineering Bulletin, 14(1):14--18, March 1991.

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