1. XML and Databases

2. Data and Document There are really at least two distinct XML uses
XML to describe Documents
XML to describe Data

3. Document vs Data Machine to machine communication Document processing
XML for documents describes complex document structures: many elements with mixed content data types usually just text
Data XML, simpler describing data structure, No or little mixed content: data types varied and important
Machine to machine communication
Document processing

4. XML Data
Xml for data is usually simpler—more straight forward in structure: less hierarchical levels, no, or very few mixed elements
It is meant to be generated and read by applications
Data types are more important—thus the use of schemas rather than DTDs

5. Reasons for XML
Explosion in the need to share data over the Internet from enterprise databases
Different database softwares, application softwares, incompatible data schemas
XML provides an easily managed format for universal communication

6. Universal Communication
Unicode Multilanguage support
Application and platform independent data format
Data logic separate from presentation logic

7. Importance to Database
David Kroenke* lists these ways in which XML is important for databases
Standard means for representing domains
Standard means for expressing database views
Clean separation of structure, content and materialization
Facility for document validity checking
Industry standards for document types
*Kroenke, David Database Processing, Eighth Edition: Prentice Hall, NJ, 2001, p 432

8. Issues XML does not always translate well to relational data models
XML has a primarily hierarchical structure
Some sort of “Data Mapping” must occur

9. Data Mapping
XML application
Database server SQL
Mapping to XML

10. Approaches to Data Mapping
Result set mapping—maps the XML to the result set of an SQL Query. (A row element is created for each record. Each column becomes an element or attribute)
Schema mapping—the database structure is generated to and from XML Schema (we will cover this more later)

11. Commercial Database Support
SQL Server—can generate XML from SQL and can update tables from XML files.
Oracle 9-I includes XSU (XML SQL Utility that will
Generate XML based on SQL queries
Extract data from XML for insert or update

12. XML Databases
There has been some talk of creating XML databases—that is a database whose native format is XML and which processes queries with XPath and XQuery
There has also been some movement to include XML as a native Data type in Relational databases

13. The Gist XML is best used to communicate data
Databases are best used to store data