Research On Efficient Queries Over Web Views

World-Wide Web (WWW) is an enormous,widely distributed,global information service center,which contains rich sources.With the popularization of network,Electronic Commerces has cought more attention from researchers.They want to take the advantage of the new commerce to gain more customs and profit.But the "data exploding"has become serious.As we are known,the users on Internet find it is a difficult problem to acquire useful information quickly.The WWW is a huge heterogeneous distributed database.To support advanced, robust and reliable applications,database functionalities need be added to WWW. This need to introduce new mechanism and concepts in order to add database functionalities to the WWW. Building a Web data query systemhas got more attention recehtly,the current is just based on the points mentioned above for further expansion in many related fields.First the paper outlines the current research status at home and abroad,introduces the significance of the paper and some relative theories.Then considering Web site's characteristics,Web data's diversity and distributed computation characteristics of net work,the paper builds a optimizing query system model based on Web Views and relates every function module in detail.Furthermore the paper integrates all modules in recommendation system model into B/S three layers based on CORBA criteria: customer layer,Server layer,database layer.Secondly, using Web data charactors,the paper is to build relational abstractions oflarge and fairly well-structured web sites and to use an optimizer to translate declarative queries on these relational abstractions to efficient navigation plans.We use a simple subset of the ARANEUS data model (ADM)to describe web sites.This ADM scheme is augmented with link constraints that capture the redundancy present in many web sites.This paper also use inclusion constraints that state that all the pages that can be accessed using a certain path can also be accessed using another path. We use a navigational algebra as the target ganguage the describes navigation plans and we show how to us rewrite rules in the spirit of relational optimizers and ,taking link and inclusion constraints into account ,to reduce the number of page accesses needed to answer a query.When a query on the relational views is issued,it is repeatedly rewritten using the rules.This process generates number of navigation plans to compute the query;the cost of these plans is then estimated based on a simple cost model that takes network accesses as the primary cost parameter.In this way,an efficient execution plan is selected for processing the query.The paper gives some validation experiment about the ability of query optimization algorithm to depict the accuracy .And at last,the paper puts forward the summarizing of the paper and next step's work.