* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Presentation summary: XML views in relational databases
Survey
Document related concepts
Expense and cost recovery system (ECRS) wikipedia , lookup
Resource Description Framework wikipedia , lookup
Semantic Web wikipedia , lookup
Concurrency control wikipedia , lookup
Information privacy law wikipedia , lookup
Data vault modeling wikipedia , lookup
Open data in the United Kingdom wikipedia , lookup
National Information Exchange Model wikipedia , lookup
Relational algebra wikipedia , lookup
Business intelligence wikipedia , lookup
Microsoft SQL Server wikipedia , lookup
Entity–attribute–value model wikipedia , lookup
Versant Object Database wikipedia , lookup
Clusterpoint wikipedia , lookup
Relational model wikipedia , lookup
Transcript
Presentation summary: XML views in relational databases Done by: El Hazoui Ilias Supervised by: Dr. Haddouti 7 October 2003 1. Definition of XML view: The definition of XML view is somewhat the same as the concept of view in the relational databases. However, the result of the XML view is an XML document. The XML view describes the shape of an XML document, even though the XML does not really exist because it is created on the fly from the relational engine. In addition, we can query this XML view as though it were a real XML document; the query, together with the view, determines the shape of the resulting XML. 2. The importance of XML view: XML has emerged as the standard data exchange format for internet-based business applications. This has created the need to publish existing business data, stored in relational databases, as XML. A general way to publish relational data as XML is to provide XML views over relational data, and allow business partners to query these views using an XML query language. 3. XML view architecture: A possible architecture is based on three components: The data server that may be a database, an XML repository, or any source capable of exporting XML data. The View server that restructures data to construct the view, possibly deals with access rights, and integrates data from several sources. An XML view document that is handled by a standard Web browser and interacts with view server to obtain data. XML View Architecture Vie w Specification Data Server Vie w Server XML Repository Vie w Docume nts (possibly virtual) XML Stylesheet Web Browser Vie w Pages External Application 4. The implementation of XML views: Many universities and research laboratories are till working on this topic to find a universal standard to make relational data viewable as XML documents; here I present some projects that support XML views: The Mediation of Information using XML (MIX) project, which is a joint effort between the San Diego Supercomputer Center and the Database Lab at the University of California San Diego. They are developing a wrapper-mediator system which employs XML as a means for information modeling, as well as interchange, across heterogeneous information sources including GIS systems, and web sites with HTML pages. However, this project is not optimized for RDBMS’s. Most commercial database systems provide a way to create views of relational data. However, most of these systems do not support queries over XML views. Microsoft’s SQL Server is the only one that supports queries over XML views, but this query support is very limited. This is because queries are specified using XPath, which is a subset of XQuery. For instance, unlike XQuery, XPath cannot specify joins. (here I’m talking about the support of the relational database system of XML views without using any other system in the top of it, and as I mentioned before, this support is limited, and that is why we are looking on a system that can fills this gap). XPERANTO middleware system allows existing relational data to be viewed and queried as XML, and which works on top of any relational database system. XPERANTO automatically creates a default XML view, which is a low-level XML view of the underlying relational database. Users can define their own views on top of the default views on top of the default view using XQuery. The main advantage of this approach is that a “standard” XML query language is used to create and query views. However, if we want to use relational database systems alone for XML views without XPERANTO, a proprietary language is to be used to define the initial XML view of the underlying relational database. High-Level Architecture of XPERANTO XQuery Query Query Result XPERANTO XQuery to SQL Converter Tagger SQL Query SQL Result Relational Database 5. My opinion: XML views provide a flexible way to view the relational data in XML. Some relational database systems provide XML views and support queries over these kinds of views. So if the user doesn’t have to use advanced queries, then there is no need to use a middleware system on top of the RDBMS. However, we can use a middleware system like XPERANTO in the top of the RDBMS if it does not support XML views, or if it can’t execute complex XML queries over the views that the RDBMS provides. The middleware takes care of everything from creating the views to executing the XML queries and giving the result as XML document. I think that there is a drawback of using the middleware system, because the user has to do some plumbing to make the middleware system works on top of the RDBMS. So, we should wait until the RDBMS companies provide a full support of the XML views in order to get rid of these middleware systems, and this is my guess to what will happen.