DBA Tips Archive for Oracle
Introduction to XML DB
by Jeff Hunter, Sr. Database Administrator
This chapter introduces you to Oracle XML DB.
From its beginnings, XML's core characteristics of self-description and dynamic extensibility have provided the flexibility needed to transport messages between various applications, and loosely couple distributed business processes.
XML is also language-independent and platform-independent. As XML support has become standard in browsers, application servers, and databases, enterprises have wished to tie legacy applications to the Web using XML to transform various proprietary file- and document-exchange templates into XML.
More recently, a new generation of XML standards, such as XML Schema, has enabled a unified data model that can address both structured data and documents. XML Schema has emerged as a key innovation in managing document content with the same rigor as data by enabling documents marked up as XML to move into the database.
Oracle XML DB is a set of built-in high-performance storage and retrieval technologies geared to XML. Oracle XML DB fully absorbs the World Wide Web Consortium (W3C) XML data model into Oracle9i database and provides new standard access methods for navigating and querying XML. You get all the advantages of relational database technology and XML technology at the same time. Oracle XML DB can be used to store, query, update, transform, or otherwise process XML, while at the same time providing SQL access to the same XML data.
Oracle XML DB is not some separate server but rather the name for a distinct group of technologies related to high-performance XML storage and retrieval that are available within the familiar Oracle database. Oracle XML DB can also be thought of as an evolution of the Oracle database that encompasses both SQL and XML data models in a highly interoperable manner, thus providing native XML support.
Benefits of XML DB
Applications often manage structured data as tables and unstructured data as files or Large Objects (LOBs). This subjects developers to different paradigms for managing different kinds of data. Systems channel application-development down either of the following paths:
- Unstructured: This typically makes document access transparent and table access complex.
- Structured: This typically makes document access complex and table access transparent.
Oracle XML DB provides the following benefits:
- The ability to store and manage both structured and unstructured data under the same standard W3C XML data model (XML Schema).
- Complete transparency and interchangeability between the XML and SQL data views.
- Valuable Repository functionality: foldering, access control, FTP, and WebDAV protocol support with versioning. This enables applications to retain the file abstraction when manipulating XML data brought into Oracle. As a result, you can store XML in the database (rendering it queryable) and at the same time access it through popular desktop tools.
- Better management of unstructured XML data by supporting
- Piecewise updates
- XML indexing
- Integrated XML text search with Oracle Text
- Multiple views on the data, including relational views for SQL access
- Enforcement of intra-document and inte- document relationships in XML documents
- Users today face a performance barrier in storing and retrieving complex XML. Oracle XML DB provides high performance and scalability for XML operations with the help of a number of specific optimizations that relate to XML-specific data-caching and memory management, query optimization on XML, special hierarchical indexes on the XML Repository, and so on.
- Enables data and documents from disparate systems to be accessed, for example, through Oracle Gateway and External Tables, and combined into a standard data model. This integrative aspect reduces the complexity of developing applications that must deal with data from different stores.
Options for Accessing Data in XML Repository
- HTTP, through the HTTP protocol handler.
- WebDav and FTP, through the WebDav and FTP protocol server.
- SQL, through Oracle Net Services including JDBC. Oracle XML DB also supports XML data messaging using Advanced Queueing (AQ) and SOAP.
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