Research On Consistency Maintenance Of Data Warehouse's Materialized View

Data Warehouse is the product of computer information development, It handles a large number of data which are used in DataBase affairs. In the Data Warehouse,Some cleaning, extraction and conversion of the date are done to achieve the goal of rapid and effective decision-making support. On-line Consistency maintaining of Materialized view is a key technology in the Data Warehouse area.Most researches of this application area are about Consistency Maintenances, and a lot of researches are based on the view definition with the key of relational tables. All of them the ECA-Key algorithm and the ECA-Key compensation algorithm are maturely used. They use direct source database as their relations inquiry, thus has avoided nonuniformity of data view.But ECA-Key algorithm works only in the condition when view definition has the source key words and the renewal inquiry's has the same sequence with the receive order. As a result of the Data Warehouse's complex application,and frequent updating and uncertain sequence under the net envirement,also as the reasons of business distribution,media and net commucation,The result that Datawarehouse receives are usually not the same with their inquery sequence,which makes the application of ECA-Key and ECA-Key compensation algorithm get narrower and narrower and their faults apper gradually.The cost of maintanence and data writing back grows rapidly because the way that the algorithm used to do total copy.To resolve those problems, we analyze some examples of ECA-Key algorithm in this paper and propose an extended mode of relational data table. Then, we will give a new algorithm to update Materialized View called Expansion which includes Expansion-DB algorithm on source database and Expansion-DW algorithm on data warehouse. In Expansion algorithm, we first extend the traditional table in the mode and then record the sequence and type of operating using the extended field. After that, we do some necessary modification in the Materialized View of data warehouse on the basis of judging the operating on the source database by several rules. In order to guaranty the consistency of the View maintanence transaction , we use the way of query notification and response confirmation in the database and data warehouse. Following introducing the soul of the Expansion algorithm, we will show some examples and prove the correctness of it.At last, we discuss the Self maintenance of Materialized View. In this section,We not only give it a definition but also analyze its properties and the rules of judging. And then we give the simple idea and some conditions of Materialized View 's Self maintenance and improve the Materialized View to Self maintenance simply.