| A conventional database system consists primarily of user application programs that are invoked when a user explicitly requests so. Execution of such programs typically results in the processing of a sequence of transactions, where each transaction is assumed to be a unit of atomicity and recovery. Concurrency control and recovery techniques are used in conventional DBMS's to preserve the serializability and the permanence requirements of database transactions.Several DBMS facilities have been proposed that would have the DBMS automatically perform some separately defined action in response to an explicit request from an application program to read or update the database. These facilities are often referred to as assertions, triggers, or rules. We refer to systems that support such rules as active DBMS.A rule consists of a triggering event, a condition to be evaluated, and an action to be executed if the condition is evaluated to be true. We refer to those actions that are initiated by the system in response to some triggering event and condition as triggered actions. How should the execution of these triggered actions be treated with respect to user transactions in an active DBMS? Are there serializability and permanence requirements associated with such actions? In this paper we propose an execution model for active DBMS's which systematically addresses such issues. The model proposed is being incorporated into a active DBMS, which we are researching and implementing.Most of the currently proposed strategies for executing triggered actions essentially consider execution of the triggered action to be part of the triggering "transaction". Within this framework, some rules may be executed immediately when the triggering event occurs and before the triggering transaction arrives at its end point, and others may be delayed until the end of the triggering "transaction". In either case, the triggered action is executed essentially as 0a linear extension of the triggering "transaction", and the atomicity requirement is applied to the combined execution. Motivated by the above observations, we propose to incorporate decoupled execution of triggered actions in an active DBMS. Decoupled execution differs from coupled execution in that the execution of the actions and/or the evaluation of the conditions may occur in separate transactions. In general, it would be useful to allow the users the flexibility of specifying when the action or the condition evaluation need be executed, and through such specifications the system may gain flexibility in scheduling.This paper use active database method in Deer Raise Manage Information System. This modus operandi can follow the workflow of deer raise field according to the field in nature. It can suggest manager when and how to defend deer or the deer house and how to confect the forage according to the deer whose are in different kind.This article adopted software engineering idea of object-orientation, according to the process of requirement, analysis, system design, object design, realization and test, adopting UML modeling mode. The main reason is: the program analysis and design of object-orientation excelled that of traditional structure, its advantage is, it is expected to solve two main problems of software engineering----the control to software complexity and the raise in software production. Besides, it also accord with the human thinking custom, and can naturally represent entity problem in the realism world, it has significant meaning for software development process. UML is a kind of modeling language with good definition, easy to express, strong function and general application. It has blended the new thought, new method and new technology in the field of software engineering. In fact, UML has become an industry standard and gained ground. Whether in field of computer, software industry and business, UML has become a unified tool used to model a variety of systems, describe system structure, business structure and business process.I ha... |
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