ORACLE. Pl/sql user's guide and reference - release 8.0, June 1997.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....for independent operation. The Mobisnap middleware extends a traditional client server SQL database system. The single server maintains the official database state. Mobile clients cache database snapshots. Applications running on mobile devices update the shared database submitting small PL SQL [13] programs, dubbed mobile transactions. During independent operation, mobile transactions are tentatively executed in the mobile clients. Later, the clients propagate these mobile transactions to the server, where the transaction programs are re executed against the official database state. Unlike ....

....must be enforced when transactions are integrated in the official database state. In Mobisnap, operations that modify the database are expressed as mobile transactions (or simply transactions where no confusion may arise) A mobile transaction is a small program written in a subset of the PL SQL [13] language. The following changes to PL SQL have been introduced: 1) commit and rollback statements end the execution of a mobile transaction, i.e. they act as a return; 2) when the result of a select into statement includes more than one (sub )row, one row is returned (instead of raising an ....

ORACLE. Pl/sql user's guide and reference - release 8.0, June 1997.

....through the submission of This work was supported in part by Praxis XXI c #Springer Verlag. Published in the Proceedings of ADBIS DASFAA 2000, September 2000 (LNCS 1884) mobile transactions . These mobile transactions are specified in an extended subset of the PL SQL language [8], allowing programmers to clearly state the intended semantics of each operation pre conditions, post conditions and different alternatives may be defined for each transaction. The final result of a mobile transaction is only determined when the transaction is performed in the central ....

....it is often necessary to rely on optimistic replication techniques to face disconnection: transactions are tentatively executed in mobile units and they are later validated and integrated in the master database. In Mobisnap, mobile transactions are defined in an imperative language based on PL SQL [8], thus allowing programmers to specify the intended semantics for each transaction, testing pre and post conditions and defining possible alternatives. In the example of Figure 1 we present two mobile transactions. In the new order transaction the precise preconditions are tested the customer ....

Oracle.: PL/SQL User's guide and reference - release 8.0. June 1997.

....they supply a classical API working in request response fashion but not in registration notification manner. Therefore, observers are forced to use API and work as polling clients, so as to receive consistent states of the system. Some commercial technologies, in particular Relational DBMSs ([21, 26]) supply low level primitives to implement a proprietary basic publish subscribe protocol not aware of transactions. In other words the changes occur in a transactional way, but the external notification changes do not. Therefore each observer should have the burden of rebuilding a consistent ....

.... are not atomically sent, so an observer would transit across a state in which only one of them has arrived, which is inconsistent. Moreover the observer is unable to know when the sequence of events caused by a single transaction has completely arrived. 3. Some systems, such as Oracle DBMS [21] and Sybase DBMS [26] offer both the functionality of the two previous cases, in that they allow notifications to be sent both when changes occur and at commit time. Moreover, the corresponding events carry some information about the transaction causing them to be fired, typically the proprietary ....

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Oracle Corporation, PL/SQL User's Guide and Reference Release 2.3, Part No. A32542-1, chapter 8, February 1996

....[13] and Schmidt s reactor and active object [26] which don t face the problem of consistency. In previous works [22, 23] we proposed a solution applyable to object oriented applications, featuring an architectural pattern based on the observation interface. In commercial DBMSs also (Oracle [25], Sybase [27] etc. the problem of making the database active is solved at a mechanism level. In order to allow the notification of changes to observers, the database architecture has been modified by adding triggers [17, 20] Triggers are pieces of code attached to database tables that can notify ....

.... to allow the notification of changes to observers, the database architecture has been modified by adding triggers [17, 20] Triggers are pieces of code attached to database tables that can notify to a given port events of insertion, deletion and update of tuples (see for example Oracle Triggers [25]) Some research prototypes of active DBMS have been developed on the basis of Event Condition Action model (ECA) and active rules model [1, 12, 10] Some examples are HiPAC [9] Starburst [29] and Chimera [6] Most of them support composite events [7] allowing internal ECA rules to be activated ....

Oracle Corporation, PL/SQL User's Guide and Reference Release 2.3, Part No. A32542-1, chapter 8, February 1996

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